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California Sparrows Return from Displacement to Maryland
Abstract
Twenty-two migratory sparrows (Zonotrichia) which had returned to their winter home at San Jose, California (1962-63), after
being displaced 2900 kilometers to Baton Rouge, Louisiana, in the winter of 1961-62, were then displaced the 3860 kilometers
to Laurel, Maryland, during the winter of 1962-63. Six of the 22 birds returned across the continent to San Jose to be recaptured
during the winter of 1963-64.
... The migration strategies in birds are commonly (e.g., Berthold 1996) assumed to differ between adult and first-time migrants, in that young birds are guided by a bearing-and-distance program (called a clock-and-compass strategy), whereas adult birds navigate toward the previously visited wintering grounds or breeding grounds. Some very impressive experiments performed by Perdeck (1958Perdeck ( , 1964Perdeck ( , 1967 and involving displacement of thousands of birds on migration form the basis of this view, and later work by Mewaldt (1964) confirmed the navigational ability in adult migrants. Perdeck displaced more than 11,000 European starlings from The Netherlands to Switzerland. ...
... In general, the banded adults were recovered in directions toward their normal wintering grounds whereas the recoveries of first-time migrants indicated that they had continued in their normal direction of migration. Later, Mewaldt (1964) displaced adult white-crowned sparrows caught on their wintering grounds in California to Eastern United States with the rather high rates of return in subsequent winters confirming the navigational ability of experienced migrants. ...
... However, Able and Able (1996) believed that celestial rotation provides the primary cue for both naïve and experienced migrants and Cochran et al. (2004) also argues that Catharus thrushes in spring apparently calibrate their magnetic compass using celestial cues. Apart from the experiments by Perdeck (1958) and Mewaldt (1964), few experiments have focused on the navigational ability of adults. Interestingly, crows displaced in the spring did not, in general, appear to compensate for displacement (Rüppell 1944). ...
For many years, orientation in migratory birds has primarily been studied in the laboratory. Although a laboratory-based setting enables greater control over environmental cues, the laboratory-based findings must be confirmed in the wild in free-flying birds to be able to fully understand how birds orient during migration. Despite the difficulties associated with following free-flying birds over long distances, a number of possibilities currently exist for tracking the long distance, sometimes even globe-spanning, journeys undertaken by migrating birds. Birds fitted with radio transmitters can either be located from the ground or from aircraft (conventional tracking), or from space. Alternatively, positional information obtained by onboard equipment (e.g., GPS units) can be transmitted to receivers in space. Use of these tracking methods has provided a wealth of information on migratory behaviors that are otherwise very difficult to study. Here, we focus on the progress in understanding certain components of the migration-orientation system. Comparably exciting results can be expected in the future from tracking free-flying migrants in the wild. Use of orientation cues has been studied in migrating raptors (satellite telemetry) and thrushes (conventional telemetry), highlighting that findings in the natural setting may not always be as expected on the basis of cage-experiments. Furthermore, field tracking methods combined with experimental approaches have finally allowed for an extension of the paradigmatic displacement experiments performed by Perdeck in 1958 on the short-distance, social migrant, the starling, to long-distance migrating storks and long-distance, non-socially migrating passerines. Results from these studies provide fundamental insights into the nature of the migratory orientation system that enables experienced birds to navigate and guide inexperienced, young birds to their species-specific winter grounds.
... 1B and 2A). This observation is consistent with prior displacement experiments from other Zonotrichia winter populations in California, which reported birds returning to wintering sites from as far as Maryland, USA (51)(52)(53). In those experiments, return rates to winter sites were highly dependent on age-return rates increased substantially for birds that were displaced during or after their second winter at the site (51)(52)(53). ...
... This observation is consistent with prior displacement experiments from other Zonotrichia winter populations in California, which reported birds returning to wintering sites from as far as Maryland, USA (51)(52)(53). In those experiments, return rates to winter sites were highly dependent on age-return rates increased substantially for birds that were displaced during or after their second winter at the site (51)(52)(53). However, while the previous golden-crowned sparrow studies quantified site fidelity at the level of the study plot, our work tracks site fidelity at the scale of the home range and shows that precision of site fidelity increases across years. ...
Animal social interactions have an intrinsic spatial basis as many of these interactions occur in spatial proximity. This presents a dilemma when determining causality: Do individuals interact socially because they happen to share space, or do they share space because they are socially linked? We present a method that uses demographic turnover events as a natural experiment to investigate the links between social associations and space use in the context of interannual winter site fidelity in a migratory bird. We previously found that golden-crowned sparrows (Zonotrichia atricapilla) show consistent flocking relationships across years, and that familiarity between individuals influences the dynamics of social competition over resources. Using long-term data on winter social and spatial behavior across 10 y, we show that i) sparrows exhibit interannual fidelity to winter home ranges on the scale of tens of meters and ii) the precision of interannual site fidelity increases with the number of winters spent, but iii) this fidelity is weakened when sparrows lose close flockmates from the previous year. Furthermore, the effect of flockmate loss on site fidelity was higher for birds that had returned in more than 2 winters, suggesting that social fidelity may play an increasingly important role on spatial behavior across the lifetime of this migratory bird. Our study provides evidence that social relationships can influence site fidelity, and shows the potential of long-term studies for disentangling the relationship between social and spatial behavior.
... Indeed, in contrast to first-time migrants, experienced migrants are able to correct for displacements (Perdeck, 1958;Mewaldt, 1964;Thorup et al., 2007;Chernetsov et al., 2008Chernetsov et al., , 2017Kishkinev et al., 2010Kishkinev et al., , 2013Kishkinev et al., , 2015Pakhomov et al., 2018) and thus have added a learned map to their orientation program (see Fig. 15.3). Interestingly, this map is also functional at locations that have not been visited previously: birds can correct their orientation appropriately when they are experimentally displaced to far away locations, where they have certainly never been before (Perdeck, 1958;Mewaldt, 1964;Thorup et al., 2007;Chernetsov et al., 2008Chernetsov et al., , 2017Kishkinev et al., 2010Kishkinev et al., , 2013Kishkinev et al., , 2015Kishkinev et al., 2021). ...
... Indeed, in contrast to first-time migrants, experienced migrants are able to correct for displacements (Perdeck, 1958;Mewaldt, 1964;Thorup et al., 2007;Chernetsov et al., 2008Chernetsov et al., , 2017Kishkinev et al., 2010Kishkinev et al., , 2013Kishkinev et al., , 2015Pakhomov et al., 2018) and thus have added a learned map to their orientation program (see Fig. 15.3). Interestingly, this map is also functional at locations that have not been visited previously: birds can correct their orientation appropriately when they are experimentally displaced to far away locations, where they have certainly never been before (Perdeck, 1958;Mewaldt, 1964;Thorup et al., 2007;Chernetsov et al., 2008Chernetsov et al., , 2017Kishkinev et al., 2010Kishkinev et al., , 2013Kishkinev et al., , 2015Kishkinev et al., 2021). If their learned map would have been based exclusively on previously experienced local landmarks, it should not have worked at unfamiliar locations. ...
The Earth's magnetic field provides potentially useful information, which birds could use for directional and/or positional information. It has been clearly demonstrated that many birds are able to sense the compass direction of the Earth's magnetic field and that they can use this information as part of a compass sense. More recently, it has also been demonstrated that at least some birds can use magnetic information to determine their approximate position on the Earth based on magnetic cues. In addition to direct uses for orientation and navigation, magnetic information also seems to be able to influence other physiological processes such as fattening and migratory motivation as a trigger for changes in behavior. While the behavioral responses to geomagnetic cues are relatively well understood, the physiological mechanisms enabling birds to sense the Earth's magnetic field are only starting to be understood and understanding the magnetic sense(s) of animals including birds remains one of the most significant unsolved problems in biology. It is very challenging to sense magnetic fields as weak as that of the Earth using only biologically available materials. Only two basic mechanisms are considered theoretically viable in small terrestrial animals: iron-particle–based magnetoreception and radical-pair–based magnetoreception. Based on current scientific evidence, both iron-particle–based magnetoreception and radical-pair–based magnetoreception mechanisms seem to exist in birds, but they seem to be used for different purposes. Plausible primary sensory molecules and a few brain areas involved in processing magnetic information have been identified in birds for each of these two types of magnetic senses. Nevertheless, we are still far away from understanding the detailed function of any of the at least two different magnetic senses existing in at least some bird species, and, at present, no primary sensory structure has been identified beyond reasonable doubt to be the source of avian magnetoreception. This is an exciting but challenging field requiring a highly multidisciplinary, stringent, scientific approach in which a number of major discoveries are likely to be made in the next one–two decades.
... [3,33,34]). Also, we do not include the possibility that birds may use map information to navigate to their migratory destination, despite of convincing evidence that migrants are able to compensate for displacements [4][5][6][35][36][37], in some cases already during their first return migration during spring [6,37]. ...
... The first compass mechanism to be discovered and explored in birds was the time-compensated sun compass [7,35]. Birds can determine the compass direction from the sun (or from sun-related cues like the skylight polarization pattern) by compensating, through their circadian clock sense, for the sun's apparent daily movement in azimuth. ...
Birds use different compass mechanisms based on celestial (stars, sun, skylight polarization pattern) and geomagnetic cues for orientation. Yet, much remains to be understood how birds actually use these compass mechanisms on their long-distance migratory journeys. Here, we assess in more detail the consequences of using different sun and magnetic compass mechanisms for the resulting bird migration routes during both autumn and spring migration. First, we calculated predicted flight routes to determine which of the compasses mechanisms lead to realistic and feasible migration routes starting at different latitudes during autumn and spring migration. We then compared the adaptive values of the different compass mechanisms by calculating distance ratios in relation to the shortest possible trajectory for three populations of nocturnal passerine migrants: northern wheatear Oenanthe oenanthe, pied flycatcher Ficedula hypoleuca, and willow warbler Phylloscopus trochilus. Finally, we compared the predicted trajectories for different compass strategies with observed routes based on recent light-level geolocation tracking results for five individuals of northern wheatears migrating between Alaska and tropical Africa. We conclude that the feasibility of different compass routes varies greatly with latitude, migratory direction, migration season, and geographic location. Routes following a single compass course throughout the migratory journey are feasible for many bird populations, but the underlying compass mechanisms likely differ between populations. In many cases, however, the birds likely have to reorient once to a few times along the migration route and/or use map information to successfully reach their migratory destination.
Electronic supplementary material
The online version of this article (10.1186/s40462-018-0126-4) contains supplementary material, which is available to authorized users.
... Thus, it is likely that the orientation strategies of experienced migrants are multisensory and involve learned maps (Mouritsen, 2003(Mouritsen, , 2013Holland, in press). Indeed, in contrast to first-time migrants, experienced migrants are able to correct for displacements (Perdeck, 1958;Mewaldt, 1964;Thorup et al., 2007;Chernetsov et al., 2008;Kishkinev et al., 2010Kishkinev et al., , 2013 and thus have added a learned map to their orientation program (see Figure 8.3). Interestingly, this map is also functional at locations that have not been visited previously: Birds can appropriately correct their orientation when they are experimentally displaced to faraway locations where they have certainly never been before (Perdeck, 1958;Mewaldt, 1964;Thorup et al., 2007;Chernetsov et al., 2008;Kishkinev et al., 2010Kishkinev et al., , 2013. ...
... Indeed, in contrast to first-time migrants, experienced migrants are able to correct for displacements (Perdeck, 1958;Mewaldt, 1964;Thorup et al., 2007;Chernetsov et al., 2008;Kishkinev et al., 2010Kishkinev et al., , 2013 and thus have added a learned map to their orientation program (see Figure 8.3). Interestingly, this map is also functional at locations that have not been visited previously: Birds can appropriately correct their orientation when they are experimentally displaced to faraway locations where they have certainly never been before (Perdeck, 1958;Mewaldt, 1964;Thorup et al., 2007;Chernetsov et al., 2008;Kishkinev et al., 2010Kishkinev et al., , 2013. If their learned map would have been based exclusively on previously experienced local landmarks, then it should not have worked at unfamiliar locations. ...
The Earth's magnetic field provides potentially useful information, which birds could use for directional and/or positional information. It has been clearly demonstrated that birds are able to sense the compass direction of the Earth's magnetic field and that they can use this information as part of a compass sense. Magnetic information could also be useful as part of a map sense, and there is a growing body of evidence that birds are able to determine their approximate position on the Earth on the basis of geo-magnetic cues. In addition to direct uses for orientation and navigation, magnetic information also seems to be able to influence other physiological processes, such as fattening and migratory motivation, as a trigger for changes in behavior. Although the behavioral responses to geomagnetic cues are relatively well understood, the physiological mechanisms enabling birds to sense the Earth's magnetic field are only starting to be understood, and understanding the magnetic sense(s) of animals, including birds, remains one of the most significant unsolved problems in biology. It is very challenging to sense magnetic fields as weak as that of the Earth using only biologically available materials. Only two basic mechanisms are considered theoretically viable in terrestrial animals: iron-mineral-based magnetoreception and radical-pair based magnetoreception. On the basis of current scientific evidence, iron-mineral-based magnetorecep-tion and radical-pair-based magnetoreception mechanisms seem to exist in birds, but they seem to be used for different purposes. Plausible primary sensory molecules and a few brain areas involved in processing magnetic information have been identified in birds for each of these two types of magnetic senses. Nevertheless, we are still far away from understanding the detailed function of any of the at least two different magnetic senses existing in some if not all bird species, and, at present, no primary sensory structure has been identified beyond reasonable doubt to be the source of avian magnetoreception. This is an exciting but challenging field in which several major discoveries are likely to be made in the next 1–2 decades.
... (homing pigeons) or familiar migratory routes (migratory birds). The results of these studies (Chernetsov et al. 2008;Mewaldt 1964;Perdeck 1958Perdeck , 1983; Thorup et al. 2007) show that birds possess the ability to choose approximately the correct direction leading towards their goal even if the direction is into unfamiliar territory, and the goal cannot be directly perceived by any sense on the initial step of movement (type III orientation, sensu Griffin 1952). The reference systems used for positioning (natural coordinates) and avian sensory systems involved in navigation are in focus of this review. ...
... Displacement experiments with birds of different age and migratory experience suggested that, during their first migration, naive birds gain navigational skills that allow them to perform true navigation later on (Mewaldt 1964;Perdeck 1958Perdeck , 1983Thorup et al. 2007). Given that, two key questions arise: (1) what kind of experience do avian migrants gain during their first migration that enables them to navigate? ...
Displacement studies have clearly shown that experienced avian
migrants are able to perform true navigation, i.e., they can find the
correct direction leading to a target destination from unfamiliar sites.
The sensory mechanisms of true navigation remain poorly understood,
though some remarkable progress has been made in the last 10–15 years.
There are two primary hypotheses explaining the sensory nature of
navigation: (1) a magnetic map hypothesis proposes that birds use
parameters of the geomagnetic field that are predictably distributed on
the globe. As for the sensory nature of this hypothesis, it has been
assumed by some researchers that the magnetic receptor cells reside in
the upper beak (the socalled
“beak organ”), and transmit information
via the trigeminal nerve to the brain; (2) an olfactory map hypothesis
assumes that birds can smell their position by taking advantage of
odours distributed in the atmosphere. There are a growing number of
studies supporting both of the hypotheses mentioned though in different
avian model species. In this review, an attempt is made to provide an
overview of the evidence for different navigational cues proposed thus
far, with the main focus on the recent studies addressing the magnetic
and olfactory navigation hypotheses. Also, a list of key open questions,
together with possible experimental approaches, is proposed.
... Birds displaced to unknown places either from their breeding sites, their wintering sites or during the migratory season have shown the ability to return and home to the breeding site either directly or to the next breeding season (e.g. Mewaldt 1964, Perdeck 1967. Thus, birds with ample experience can in addition to compass information rely on map information presumably gathered on their previous migration(s) to locate already known stopover, wintering and breeding areas (map-and compass concept;Berthold 2003) and there is also convincing evidence that birds are able to use a navigational map (Fischer et al. 2003). ...
... First indications of navigation abilities in migratory songbirds came from Perdeck (1958) and Mewaldt (1964) that showed that displaced adult birds were capable of returning to their species-specific wintering sites after displacement. Fischer et al. (2003) showed that at least one of the parameters used for navigation by adult Australian silvereyes were magnetic cues, most probably inclination or total intensity. ...
... First we consider how modern tracking studies might help contribute to our understanding of navigational abilities and spatiotemporal representational strategies. Adult migratory birds (and perhaps other life stages) display a stunning ability to return to the same breeding, overwintering and even stopover sites during repeated migrations (Moreau, 1972; Mouritsen, 2003), and more importantly, they can do so (or at least start to do so) following both passive and experimental displacements from familiar routes or locations (Chernetsov et al., 2008; Mewaldt, 1964; Perdeck, 1958; Thorup et al., 2007). This capacity is usually explained as the result of true navigation (sensu Griffin, 1952). ...
... However, there are only a few experimental studies that infer or track movements of migrants in free-flight followingTable 1. Example contrasts over which the tracks of migrant birds might be compared, with examples of the type of navigational questions the comparison might inform and the type of track differences to look for Contrast E x ample navigational interest W h at to look Fewer atypical routes in social migrants ability with the diminishing angle of magnetic dip (inclination) near the equator? experimental displacement, such as the band-recapture studies of starlings [Sturnus vulgaris (Perdeck, 1958)] and white-crowned sparrows [Zonotrichia leucophrys (Mewaldt, 1964)], the satellite tracking of white storks [Ciconia ciconia (Chernetsov et al., 2004)] and the short-range transmitter tracking of white-crowned sparrows (Thorup et al., 2007). Envisioning a future that will enable the long-range tracking of migrant songbirds over the course of a complete migration cycle, including experimental displacements, offers unparalleled opportunities for understanding the properties, capacity and limits of migrant navigational ability. ...
Birds have remained the dominant model for studying the mechanisms of animal navigation for decades, with much of what has been discovered coming from laboratory studies or model systems. The miniaturisation of tracking technology in recent years now promises opportunities for studying navigation during migration itself (migratory navigation) on an unprecedented scale. Even if migration tracking studies are principally being designed for other purposes, we argue that attention to salient environmental variables during the design or analysis of a study may enable a host of navigational questions to be addressed, greatly enriching the field. We explore candidate variables in the form of a series of contrasts (e.g. land vs ocean or night vs day migration), which may vary naturally between migratory species, populations or even within the life span of a migrating individual. We discuss how these contrasts might help address questions of sensory mechanisms, spatiotemporal representational strategies and adaptive variation in navigational ability. We suggest that this comparative approach may help enrich our knowledge about the natural history of migratory navigation in birds.
... The hypothesis also depends on the assumption that birds imprint on the geographical variation of the Earth's magnetic field during their first outbound migration towards their non-breeding areas and later extrapolate spatial gradients to determine their position [18,19]. Accordingly, experienced birds that artificially experienced the geomagnetic field of an unfamiliar location by virtual displacement [18,20,21] or were physically translocated to outside the individual's known route [19,22], were found to correct their displacements. This would also explain why the magnetic-particle sensor is affected by the magnetic pulse treatment only in adults, performing true navigation, but not in juveniles, which on their first migration have to first learn the map and orient only by a compass [2]. ...
Migratory songbirds may navigate by extracting positional information from the geomagnetic field, potentially with a magnetic-particle-based receptor. Previous studies assessed this hypothesis experimentally by exposing birds to a strong but brief magnetic pulse aimed at remagnetizing the particles and evoking an altered behaviour. Critically, such studies were not ideally designed because they lacked an adequate sham treatment controlling for the induced electric field that is fundamentally associated with a magnetic pulse. Consequently, we designed a sham-controlled magnetic-pulse experiment, with sham and treatment pulse producing a similar induced electric field, while limiting the sham magnetic field to a value that is deemed insufficient to remagnetize particles. We tested this novel approach by pulsing more than 250 wild, migrating European robins (Erithacus rubecula) during two autumn seasons. After pulsing them, five traits of free-flight migratory behaviour were observed, but no effect of the pulse could be found. Notably, one of the traits, the migratory motivation of adults, was significantly affected in only one of the two study years. Considering the problem of reproducing experiments with wild animals, we recommend a multi-year approach encompassing large sample size, blinded design and built-in sham control to obtain future insights into the role of magnetic-particle-based magnetoreception in bird navigation.
... Information from this unknown sensor is neither necessary nor sufficient for a functional magnetic compass, but instead could contribute important components of a multifactorial "map" for global positioning. Positional information could allow migratory birds to make vitally important dynamic adaptations such as migratory restlessness behaviour, fuel deposition, and/or directional orientation have been shown to be modified by magnetic fields (Perdeck 1958;Mewaldt 1964;Beck and Wiltschko 1988;Wiltschko and Wiltschko 1992;Fransson et al. 2001;Kullberg et al. 2003;Thorup et al. 2007;Boström et al. 2010;Henshaw et al. 2010;Kishkinev et al. 2015;Bulte et al. 2017). Thus, in addition to the well-known magnetic "compass" sense (Wiltschko and Wiltschko 1972;Cochran et al. 2004;Zapka et al. 2009), it is conceivable that birds could use magnetic "map" or "signpost" parameters for global positioning and to adapt their behaviour accordingly. ...
The Earth's magnetic field is one of several natural cues, which migratory birds can use to derive directional ("compass") information for orientation on their biannual migratory journeys. Moreover, magnetic field effects on prominent aspects of the migratory programme of birds, such as migratory restlessness behaviour, fuel deposition and directional orientation, implicate that geomagnetic information can also be used to derive positional ("map") information. While the magnetic "compass" in migratory birds is likely to be based on radical pair-forming molecules embedded in their visual system, the sensory correlates underlying a magnetic "map" sense currently remain elusive. Behavioural, physiological and neurobiological findings indicate that the sensor is most likely innervated by the ophthalmic branch of the trigeminal nerve and based on magnetic iron particles. Information from this unknown sensor is neither necessary nor sufficient for a functional magnetic compass, but instead could contribute important components of a multifactorial "map" for global positioning. Positional information could allow migratory birds to make vitally important dynamic adaptations of their migratory programme at any relevant point during their journeys.
... Wild birds-sea birds, aerial birds as well as small passerines-returned when displaced from their nests during breeding, but also during the winter season, with the homing success depending on the distance of displacement, the size of the birds' home range and their ability to perform long, enduring flights. Wintering migrants-passerines, shorebirds, and others-have also been found to return to their winter home after displacement (e.g., Baillon et al. 1992;Baccetti et al. 1999); wintering sparrows of the genus Zonotrichia, displaced across the American continent, returned during following winter (Mewald 1964) (for a review on displacement experiments with wild birds and corresponding references, see Wiltschko 1992). These experiments document the general homing ability of birds, and their navigational capacities formed a solid baseline when some species began to develop a migratory lifestyle, flying even longer distances when moving their home range from one region to a distant other one twice a year. ...
Experiments with migrating birds displaced during autumn migration outside their normal migration corridor reveal two different navigational strategies: adult migrants compensate for the displacement, and head towards their traditional wintering areas, whereas young first-time migrants continue in their migratory direction. Young birds are guided to their still unknown goal by a genetically coded migration program that indicates duration and direction(s) of the migratory flight by controlling the amount of migratory restlessness and the compass course(s) with respect to the geomagnetic field and celestial rotation. Adult migrants that have already wintered and are familiar with the goal area approach the goal by true navigation, specifically heading towards it and changing their course correspondingly after displacement. During their first journey, young birds experience the distribution of potential navigational factors en route and in their winter home, which allows them to truly navigate on their next migrations. The navigational factors used appear to include magnetic intensity as a component in their multi-modal navigational ‘map’; olfactory input is also involved, even if it is not yet entirely clear in what way. The mechanisms of migratory birds for true navigation over long distances appear to be in principle similar to those discussed for by homing pigeons.
... The method involved tying an identification tag/band in bird's leg before releasing. Many migratory route displacement experiments on starlings [44] and white-crowned sparrows [45] used banding method. This method needed large sample size for effectiveness thus was often replaced by mass-marking and larger numbers of observing location and personnel. ...
How migrating animals find their direction to reach migratory destination is an important question of wildlife migration. Animals use a variety of geophysical cues such as the sun compass, stellar constellation, and geomagnetic field of the Earth to accomplish this feat. Endogenous clocks facilitate, to some extent, the challenge of heading toward the right direction. Whereas extensive body of research has focused on the biophysical and neurobiological mechanisms, relatively less is known of the extent of involvement of biological clocks in the migratory orientation. Studies on the innate capability of first year migrants and experimentally displaced experienced migrants to correctly reach their destination indicate that an endogenous time program controls spontaneous changes during the course of migratory journey. Here, we intend to briefly summarize the orientation studies in animals, with emphasis placed on the role of biological clocks in the avian orientation.
... Documenting whether juvenile migrants travel independently of adults and whether they follow the same routes as adults has not been possible for smaller species because the necessary technology was unavailable [5]. Similarly, lack of suitable technology has hindered the study of how the inherited spatiotemporal guiding programme unfolds in free-flying individuals, for instance in route learning [6] and dealing with wind drift [7]. Common cuckoos Cuculus canorus are long-distance migrants wintering in Tropical Africa [8]. ...
Being an obligate parasite, juvenile common cuckoos Cuculus canorus are thought to reach their African wintering grounds from Palearctic breeding grounds without guidance from experienced conspecifics but this has not been documented. We used satellite tracking to study naïve migrating common cuckoos. Juvenile cuckoos left breeding sites in Finland moving slowly and less consistently directed than adult cuckoos. Migration of the juveniles (N = 5) was initiated later than adults (N = 20), was directed toward the southwest–signifi-cantly different from the initial southeast direction of adults–and included strikingly long Bal-tic Sea crossings (N = 3). After initial migration of juvenile cuckoos toward Poland, the migration direction changed and proceeded due south, directly toward the winter grounds, as revealed by a single tag transmitting until arrival in Northwest Angola where northern adult cuckoos regularly winter. Compared to adults, the juvenile travelled straighter and faster, potentially correcting for wind drift along the route. That both migration route and timing differed from adults indicates that juvenile cuckoos are able to reach proper wintering grounds independently, guided only by their innate migration programme.
... However, the birds we displaced likely did not know the location of the closest breeding habitat when they were released (the boreal forest was ~ 50 km directly north). In addition, the migratory orientation and the return rates of translocated white-and golden-crowned sparrows suggests that these closely-related species retain their motivation to fly back to wintering or breeding sites after long-distance displacements (up to 3,900 km 8,9 ). ...
The ability to navigate implies that animals have the capability to compensate for geographical
displacement and return to their initial goal or target. Although some species are capable of
adjusting their direction after displacement, the environmental cues used to achieve this remain
elusive. Two possible cues are geomagnetic parameters (magnetic map hypothesis) or
atmospheric odour-forming gradients (olfactory map hypothesis). In this study, we examined
both of these hypotheses by surgically deactivating either the magnetic or olfactory sensory
systems in experienced white-throated sparrows (Zonotrichia albicollis) captured in southern
Ontario, Canada, during spring migration. Treated, sham-treated, and intact birds were then
displaced 2,200 km west to Saskatchewan, Canada. Tracking their initial post-displacement
migration using an array of automated VHF receiving towers, we found no evidence in any of
the groups for compensatory directional response towards their expected breeding grounds. Our
results suggest that white-throated sparrows may fall back to a simple constant-vector orientation
strategy instead of performing true navigation after they have been geographically displaced to
an unfamiliar area during spring migration. Such a basic strategy may be more common than
currently thought in experienced migratory birds and its occurrence could be determined by
habitat preferences or range size.
... Experienced songbird migrants can perform true navigation involving the use of a map sense to identify the position of the current location in relation to a goal, enabling them to compensate for a displacement, even outside familiar areas 5 . This has been documented using various methods based on migration directions of displaced birds, such as ring recoveries 6,7 , radio tracking 8,9 , and orientation cages [10][11][12] . However, the actual movement paths are critical to understand the processes of navigation 3 and only recent development of remote tracking technologies has made this now possible 13 . ...
Migrating birds follow innate species-specific migration programs capable of guiding them along complex spatio-temporal routes, which may include several separate staging areas. Indeed, migration routes of common cuckoos Cuculus canorus show little variation between individuals; yet, satellite tracks of 11 experimentally displaced adults revealed an unexpected flexibility in individual navigation responses. The birds compensated for the translocation to unfamiliar areas by travelling toward population-specific staging areas, demonstrating true navigation capabilities. Individual responses varied from travelling toward the first stopover in northern Europe to flying toward the Central-African winter grounds, the latter including several stopovers in unfamiliar areas. Apparently, the cuckoos possess spatial knowledge far beyond their population-specific flyway scale, and make individual decisions likely based on an assessment of perceived gain and cost of alternative route options.
... Most experiments documenting the homing behaviour of wild birds have been displacement tests performed during the breeding season. Less attention has been paid to the question whether birds also home when displaced from their wintering sites (Mewaldt 1964, Benvenuti and Ioalè 1980, Ioalè and Benvenuti 1983. ...
Homing behaviour of displaced wild birds are largely unexplored, with the exception of the orientation and homing performance of pigeons (Columba livia), which are well documented. Using the redwing (Turdus iliacus) and the fieldfare (T. pilaris) as an example of typical nocturnal and diurnal/nocturnal migrant species, respectively, homing movements of birds following displacements were investigated. A total of 16 colour-ringed birds were displaced over distances of 6 to 22.5 km in several directions from their nesting territories. In these displacement experiments 8 out of 12 redwings and 2 out of 4 fieldfares were observed to return to their home territories. Most of them were observed at their nest sites the following morning after the release, i. e. their return took less than one day. The pooled movement directions in cage and release experiments by individual birds showed a significant preference for the home direction. There was seemingly no difference between birds' headings under clear or overcast skies. Assumption is made that migrants returning to previously occupied nesting sites perform behaviour analogous to that of a homing pigeon. Redwings, for example, exhibit a high degree of site fidelity with respect to previous breeding sites. Therefore, it is assumed that, in general, captured redwings displaced and released in entirely unfamiliar areas could home by true navigation.
... The demonstrated ability of migratory birds to return exactly 'home', quickly and efficiently, after a considerable experimental spatial displacement (Mewaldt 1964, Akesson 2003 indicates that birds can be considered to have the equivalent of a GPS system (Thorup et al. 2007a, Thorup & Holland 2009). Navigation can only take place, however, when the final destination is known, but there is no evidence to date of genetic programs that provide na€ ıve migrants with instructions on how to reach wintering sites at a specific location on a small (< 100 km) or medium (100-1000 km) scale. ...
In most long-distance migratory birds, juveniles migrate without their parents and so are likely to lack detailed knowledge of where to go. This suggests the potential for stochasticity to affect their choice of wintering area at a large scale (> 1000 km). Adults, in contrast, may re-use non-breeding sites that promote their survival, so removing uncertainty from their subsequent migrations. I review the evidence for large-scale stochastic juvenile site selection followed by adult site fidelity, and then develop a ‘serial-residency’ hypothesis based on these two traits as a framework to explain both the migratory connectivity and the population dynamics of migrant birds and how these are affected by environmental change. Juvenile stochasticity is apparent in the age-dependent effects of weather or experimental displacement on the outcome of migration and in the very wide variation in the destinations of individuals originating from the same area. Adults have been shown to be very faithful to their wintering grounds and even to staging sites. The serial residency hypothesis predicts that migrants that show these two traits will rely on an individually unique but fixed series of temporally and spatially linked sites to complete their annual cycle. As a consequence, migratory connectivity will be apparent at a very small scale for individuals, but only at a large scale for a population, and juveniles are predicted to occur more often at less suitable sites than adults, so that survival will be lower for juveniles. Migratory connectivity will arise only through spatial and temporal autocorrelation with local environmental constraints, particularly on passage, and the distribution and age structure of the population may reflect past environmental constraints. At least some juveniles will discover suitable habitat that they may re-use as adults, thus promoting overall population-level resilience to environmental change, and suggesting value in site-based conservation. However, because migratory connectivity only acts on a large scale, any population of migrants will contain individuals that encounter a change in suitability somewhere in their non-breeding range, so affecting average survival. Differences in population trends will therefore reflect variation in local breeding output added to average survival from wintering and staging areas. The latter is likely to be declining given increasing levels of environmental degradation throughout Africa. Large-scale migratory connectivity also has implications for the evolutionary ecology of migrants, generally because this is likely to lead to selection for generalist traits.
... In migratory Zonotrichia spp. Mewaldt and associates have reported remarkable instances of long-distance homing by birds displaced from their wintering sites (Roadcap 1962;Mewaldt 1963Mewaldt ,1964aMewaldt , 1964b; see also Manwell 1962). In most of these cases, displacement and recovery were separated by a long interval, so that it is likely that the birds migrated to the breeding range after displacement, and then in the following autumn migrated back to the place from which they had been taken during the preceding winter. ...
SHORT COMMUNICATIONS 539 GLADSTONE, D. E. 1979. Promiscuity in monogamous colonial birds. Am. Nat. 114:545-577. HINDE, R. A. 1970. Animal Behaviour. McGraw-Hill, New York. HOHN, E. 0. 1947. Sexual behaviour and seasonal changes in the gonads and adrenals of the mallard. Proc. Zool. Sot. Lond. 117:28 l-304. HOUSTON, D. C. 1976. Breeding of the White-backed and Ruppell’s Griffon Vultures, Gv~s africanus and G. ruep&llii. Ibis
... Interessanterweise befanden sich unter den nach Maryland verfrachteten V6geln auch die 22 Rackkehrer aus Louisiana, die mindestens zum zweiten, wahrscheinlich aber zum dritten Mal tiberwinterten. Von ihnen kehrten sechs im n~ichsten Winter nach Kalifornien zurfick; ihre Rtickkehrrate lag mit 27,3 % sogar noch fiber den 21%, die in den kalifornischen Fanggebieten als Mittelwert der Rfickkehr von Jahr zu Jahr ermittelt wurden (Mewaldt 1964). Dies lfiBt sich wohl auf die durch die vorausgegangene Verfrachtung gewonnene ausgedehnte Erfahrung dieser V6gel zurtickffihren (vgl. ...
Many migratory birds show philopatry, i.e. they regularly breed and winter at the same sites. The routes taken by migrants are adjusted to the geographical and ecological conditions between breeding and wintering areas, often resulting in indirect paths. Young birds on their first migration face the task of reaching the as yet unknown population-specific winter quarters with the help of innate information. Large-scale displacement experiments with migrants and cage experiments with hand-raised birds revealed that this innate information is given as direction and distance, with the distance controlled by an endogenous time program that determines amount and temporal distribution of migratory activity. Both, migratory activity and direction - or, in the case of indirect routes, a sequence of directions - are genetically transmitted from one generation to the next. Birds use two reference systems to convert innate directional information into an actual flying course: celestial rotation and the geomagnetic field. Celestial rotation produces a reference direction opposite from its center, which is obtained by observing the diurnal and/or the nocturnal sky. This reference can be used to establish a star compass, not only utilizing the natural, but also artificial 'stars', provided the birds can observe these 'stars' rotating. However, with only stars available, migrants that normally prefer southwesterly courses show southerly tendencies, apparently unable to convert the population-specific components of their migratory direction. Birds raised with only magnetic cues available, in contrast, are well oriented in their population-specific migratory direction, except in areas with steep inclination; here, the magnetic field provides only an axis, and birds also need celestial rotation for unimodal orientation. As the birds' magnetic compass is an inclination compass, migrants of the northern and southern hemisphere may use the same migratory program, starting out 'equatorwards' in autumn. During the premigratory period, both reference systems interact to determine the migratory course. If North indicated by celestial rotation and magnetic North diverge, celestial rotation proves dominant, resulting in a changed magnetic compass course.
... Funnel studies have been combined with data from radar, and more recently from lightsticks (phosphorescent material attached to the tail or lower back of bird so its direction of flight can be seen as it departs into the night) and ceilometers (powerful beams of light pointed into the sky; Zehnder et al. 2001), enabling researchers to follow individual behaviors in nature for a short period. Displacement experiments, which involve the capture and translocation of individuals off their usual migration route, with subsequent study of how animals shift migratory direction and timing, still form the basis of our current understanding of the orientation and navigation of free-flying birds (Perdeck 1958;Mewaldt 1960). ...
Recent technological innovation has opened new avenues in migration research – for instance, by allowing individual migratory animals to be followed over great distances and long periods of time, as well as by recording physiological information. Here, we focus on how technology – specifically applied to bird migration – has advanced our knowledge of migratory connectivity, and the behavior, demography, ecology, and physiology of migrants. Anticipating the invention of new and smaller tracking devices, in addition to the ways that technologies may be combined to measure and record the behavior of migratory animals, we also summarize major conceptual questions that can only be addressed once innovative, cutting-edge instrumentation becomes available.
... Others have suggested that migrants obtain orientation cues from the setting sun (solar compass or polarized light) as they sit quietly at dusk (Krantz & Gauthreaux, 1975;Moore, 1987, Sandberg et al., 1991Cochran et al., 2004). GWCS use solar and celestial cues for orientation during migration (Mewaldt, 1964;Åkesson et al., 1996, 2001. Taken together, the quiescent phase may serve as both a time to complete anabolic functions and accumulate environmental information relevant to orientation at time of departure. ...
Gambel's white-crown sparrow (Zonotorichia leucophrys gambelii) is a long-distance, over-land migrant. In captivity birds display many characteristics of the autumn and spring migratory life history stages that include hyperphagia, fattening and high intensity nocturnal activity termed migratory restlessness or Zugunruhe. We recorded the behaviour of captive birds while simultaneously collecting 24 h locomotor activity. These data were used to define the behaviour displayed by captive birds during autumn and spring in order to compare the two migratory stages and to draw inferences for free-living birds. The predominant behaviour during day and nighttime was rest. Feeding occurred only during daylight hours but at a greater frequency in autumn than spring. Birds generally used their feet as the primary source of locomotion during the day termed 'jump'. During the night, two distinct behaviours, 'beak-up flight' and 'beak-up' involving high intensity wing motions were observed and considered components of migratory restlessness. The frequency of the 'beak-up flight' was greatest during spring and associated with the enhanced tempo of vernal migration. In both stages, migratory restlessness was preceded by a quiescent phase, the occurrence of which differed and related to time available for foraging and length of the night. Given these findings, we hypothesize that diel behaviours displayed by autumn and spring migrants in captivity highlight distinctions between the two life history stages.
... White-crowned sparrows breed in the northern part of Canada and winter in the southern U.S.A. (Chilton et al. 1995). The population of whitecrowned sparrows breeding in the area of Inuvik spends the winter in southwestern U.S.A. (Mewaldt 1964;Chilton et al. 1995). Thus, their expected autumn migration course towards geographical southeast follows an initial great circle route of ca. ...
The migratory orientation of juvenile white-crowned sparrows, Zonotrichia leucophrys gambelli, was investigated by orientation cage experiments in manipulated magnetic fields performed during the evening twilight period in northwestern Canada in autumn. We did the experiments under natural clear skies in three magnetic treatments: (1) in the local geomagnetic field; (2) in a deflected magnetic field (mN shifted −90°); and (3) after exposure to a deflected magnetic field (mN −90°) for 1 h before the cage experiment performed in the local geomagnetic field at dusk. Subjects showed a mean orientation towards geographical east in the local geomagnetic field, north of the expected migratory direction towards southeast. The sparrows responded consistently to the shifted magnetic field, demonstrating the use of a magnetic compass during their first autumn migration. Birds exposed to a cue conflict for 1 h on the same day before the experiment, and tested in the local geomagnetic field at sunset, showed the same northerly orientation as birds exposed to a shifted magnetic field during the experiment. This result indicates that information transfer occurred between magnetic and celestial cues. Thus, the birds' orientation shifted relative to available sunset and geomagnetic cues during the experimental hour. The mean orientation of birds exposed to deflected magnetic fields prior to and during testing was recorded up to two more times in the local geomagnetic field under natural clear and overcast skies before release, resulting in scattered mean orientations.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .
... Night-migrating songbirds travel to and from their wintering and breeding areas often separated thousands of kilometers apart and are clearly capable of finding intended goal areas from a distant location (Mewaldt 1964; Perdeck 1974). Studies of navigational strategies used by migratory birds have mostly concentrated on juveniles undertaking their first migration in autumn. ...
Night-migrating song birds travel to and from their wintering and breeding areas often separated thousands of kilometers apart and are clearly capable of finding
intended goal areas from a distant location. Displacement experiments provide a useful way to highlight orientation and navigational skills in migrants. To investigate which cues birds actually use to compensate for displacement and
the exact mechanism of each cue, experiments with manipulation of single cues are required. We conducted a simulated displacement of lesser whitethroats Sylvia curruca on spring migration. Birds were displaced not geographically but in geomagnetic space only, north and south of their breeding area to test whether they incorporate information from the geomagnetic field to find their breeding area. Lesser whitethroats held in southeast Sweden but experiencing a simulated displacement north of their breeding area (Norway) failed to show a consistent direction of orientation, whereas birds displaced south of their breeding area (Czech Republic) exhibited consistent northerly orientation, close to
the expected seasonally appropriate direction, after displacement toward the trapping location. The absence of a clear compensatory direction in birds displaced north might be due to unfamiliar magnetic information or lack of sufficient information such as a magnetic gradient when moving around. By isolating one orientation cue, the geomagnetic field, we have been able to show that lesser whitethroats might incorporate geomagnetic field information to determine latitude during spring migration.
... Both the displaced (sites 3^5) and control (site 1) birds showed east to southeasterly mean orientations relative to geographical north under clear sky conditions (table 3 and ¢gure 2a^c). The birds' mean orientation did not di¡er from the expected migratory directions along an initial great circle route of 1358 or a rhumb line route of 1518 (Imboden & Imboden 1972) leading from Inuvik to the likely wintering area in the southwestern USA (Mewaldt 1964; Chilton et al. 1995) except for juvenile birds at sites 1 and 3. The mean orientation of all birds only di¡ered signi¢cantly from the expected migratory direction along a rhumb line route in the breeding area (p 5 0.05) (table 3) due to a more easterly orientation in juvenile birds. ...
The Earth's magnetic field and celestial cues provide animals with compass information during migration. Inherited magnetic compass courses are selected based on the angle of inclination, making it difficult to orient in the near vertical fields found at high geomagnetic latitudes. Orientation cage experiments were performed at different sites in high Arctic Canada with adult and young white-crowned sparrows (Zonotrichia leucophrys gambelii) in order to investigate birds' ability to use the Earth's magnetic field and celestial cues for orientation in naturally very steep magnetic fields at and close to the magnetic North Pole. Experiments were performed during the natural period of migration at night in the local geomagnetic field under natural clear skies and under simulated total overcast conditions. The experimental birds failed to select a meaningful magnetic compass course under overcast conditions at the magnetic North Pole, but could do so in geomagnetic fields deviating less than 3 degrees from the vertical. Migratory orientation was successful at all sites when celestial cues were available.
Migrating animals perform astonishing seasonal movements by orienting and navigating over thousands of kilometres
with great precision. Many migratory species use cues from the sun, stars, landmarks, olfaction and the Earth’s magnetic
field for this task. Among vertebrates, songbirds are the most studied taxon in magnetic-cue-related research. Despite
multiple studies, we still lack a clear understanding of when, where and how magnetic cues affect the decision-making
process of birds and hence, their realised migratory behaviour in the wild. This understanding is especially important
to interpret the results of laboratory experiments in an ecologically appropriate way. In this review, we summarise the
current findings about the role of magnetic cues for migratory decisions in songbirds. First, we review the methodological
principles for orientation and navigation research, specifically by comparing experiments on caged birds with experiments
on free-flying birds. While cage experiments can show the sensory abilities of birds, studies with free-flying birds
can characterise the ecological roles of magnetic cues. Second, we review the migratory stages, from stopover to endurance
flight, in which songbirds use magnetic cues for their migratory decisions and incorporate this into a novel conceptual
framework. While we lack studies examining whether and when magnetic cues affect orientation or navigation
decisions during flight, the role of magnetic cues during stopover is relatively well studied, but mostly in the laboratory.
Notably, many such studies have produced contradictory results so that understanding the biological importance of magnetic
cues for decisions in free-flying songbirds is not straightforward. One potential explanation is that reproducibility of
magnetic-cue experiments is low, probably because variability in the behavioural responses of birds among experiments
is high. We are convinced that parts of this variability can be explained by species-specific and context-dependent reactions
of birds to the study conditions and by the bird’s high flexibility in whether they include magnetic cues in a decision
or not. Ultimately, this review should help researchers in the challenging field of magnetoreception to design experiments
meticulously and interpret results of such studies carefully by considering the migration ecology of their focal species.
Common cuckoos Cuculus canorus are obligate nest parasites yet young birds reach their distant, species-specific wintering grounds without being able to rely on guidance from experienced conspecifics – in fact they never meet their parents. Naïve marine animals use an inherited navigational map during migration but in inexperienced terrestrial animal migrants unequivocal evidence of navigation is lacking. We present satellite tracking data on common cuckoos experimentally displaced 1,800 km eastward from Rybachy to Kazan. After displacement, both young and adult travelled similarly towards the route of non-displaced control birds. The tracking data demonstrate the potential for young common cuckoos to return to the species-specific migration route after displacement, a response so far reported exclusively in experienced birds. Our results indicate that an inherited map allows first-time migrating cuckoos to locate suitable wintering grounds. This is in contrast to previous studies of solitary terrestrial bird migrants but similar to that reported from the marine environment.
Within the animal kingdom, birds are unrivalled at covering large distances quickly and passing over geographic barriers. They use this power to reach food supplies, go where environment conditions are most suitable, and escape predators. Many bird species are migratory and regularly shuttle between winter and summer quarters, which may be far apart. The marked site fidelity of most species both when breeding and in winter, often even at stop-over sites, makes birds an ideal object of homing studies.
This book presents an up-to-date, detailed and thorough review of the most fascinating ecological findings of bird migration. It deals with all aspects of this absorbing subject, including the problems of navigation and vagrancy, the timing and physiological control of migration, the factors that limit their populations, and more. Author, Ian Newton, reveals the extraordinary adaptability of birds to the variable and changing conditions across the globe, including current climate change. This adventurous book places emphasis on ecological aspects, which have received only scant attention in previous publications. Overall, the book provides the most thorough and in-depth appraisal of current information available, with abundant tables, maps and diagrams, and many new insights. Written in a clear and readable style, this book appeals not only to migration researchers in the field and Ornithologists, but to anyone with an interest in this fascinating subject. * Hot ecological aspects include: various types of bird movements, including dispersal and nomadism, and how they relate to food supplies and other external conditions * Contains numerous tables, maps and diagrams, a glossary, and a bibliography of more than 2,700 references * Written by an active researcher with a distinguished career in avian ecology, including migration research.
How birds manage to find their way around in the world has long been a source of fascination. These animals range widely when foraging for food, sometimes traveling 100 km or more from their nest or roost. Moreover, many species of birds fly long distances between breeding grounds and wintering areas, returning with extraordinary precision to specific locales year after year. Distances traveled during such migrations typically average between 1000 and 6000 km each way between breeding and wintering grounds. Several species of birds travel close to 30,000 km annually between arctic breeding grounds and wintering areas in or near the antarctic. It would seem that birds, as well as other animals which forage and migrate over large distances, must possess navigational abilities of a fair degree of sophistication. Indeed, given the essential importance to such animals of an accurate and fail-safe navigational system, one might not be surprised to find that evolution has been opportunistic in exploiting available environmental sources of navigationally useful information.
Many avian migrants perform the most impressive long-distance flights between breeding and wintering areas sometimes located several thousands of kilometres apart. These birds clearly have adapted to a mobile life style where fuel economy and navigation performance must have played a major role in the selection process shaping these extraordinary abilities. Perhaps one of the most fascinating capabilities is the solo migration flights by many young migratory songbirds, for which a complete migration program inherited from their parents is stored in their genes coding flight distance and direction, which enables the individual bird to fly completely alone from the site of birth to a sometimes very distant wintering area (for review see Berthold 1996). However, not less impressive is the ability possessed by many birds to relocate known sites of importance, like breeding sites, wintering territories and even stopover sites located between these areas (e.g. Mewaldt 1964; Per-deck 1967; Moreau 1972). Furthermore, each individual bird must possess the capability of performing a diverse array of behaviours to cope with navigational tasks over distances of a few meters up to several thousands of kilometres. For instance, most birds are central place foragers during the breeding period with short-distance movements within their home range. The functional characteristics of the navigational program and the cues that are of importance to locate known sites are, however, not very well known. In navigation studies of birds mainly homing pigeons, Columba livia, have been used for experimental convenience (for recent reviews see, for example, Papi 1982, 1991; Walcott 1996; Wallraff 1991, 2001), and much less effort have been invested in studying similar phenomena in migratory birds (e.g. Alerstam 1991; Berthold 1996; Matthews 1968; Wiltschko 1989). Therefore, detailed understanding of long-distance navigation in migratory birds is still very limited.
Migratory birds have a number of navigational tools available for finding their way during long-distance migration. For passerines, these are known to include a magnetic compass (e.g. Wiltschko 1968; Wiltschko and Wiltschko 1972, 1995, 1996; Mouritsen 1998a), a celestial compass (e.g. Emlen 1967a,b, 1970, 1972, 1975; Schmidt-Koenig et al. 1991; Mouritsen 1998a; Mouritsen and Larsen 2001), a circannual clock (e.g. Gwinner 1986, 1996; Berthold 1973, 1991, 1998; Gwinner and Wiltschko 1978) and an inherited mean migratory direction (e.g. Berthold et al. 1992; Helbig 1996; Berthold 1999). We also know that some, if not all, birds have a map used for homing (e.g. Keeton 1973; Wallraff 1991; Able 1996; Bingman 1998). This chapter seeks to answer the question: How do migratory birds integrate the navigational information from these tools into an orientation strategy?
According to current theory young passerine migrants on their first migration are equipped with a genetic programme of duration and direction of migration which enables them to reach their winter quarters independently of adults. The question was investigated whether in birds prevented from gathering migratory experience the genetically determined directional information is expressed only during the first autumn migratory season or whether it is retained as an endogenous directional preference at least throughout the 2nd year of life.
A theoretical model of the phylogenetic and ontogenetic development of bird orientation is presented where navigation is taken to be phylogenetically older than migratory orientation. Starting out from orientation by landmarks and the ability for compass orientation birds are assumed to use route reversal based on compass orientation to become familiar with the distribution of landmarks and thus to form a directionally oriented integrative picture of the distribution of landmarks, the "mosaic map", for orientation within the home range. Applying the same mechanisms to factors with the nature of gradients results in a learned grid of coordinates, the "navigational map", allowing homing from unfamiliar terrain by extrapolation. Additionally, migratory birds are assumed to have innate information on the direction and distance of their migration, the direction being genetically fixed using as a reference system the compass already developed for orientation within the home range. /// Представлена теоритическая модель филогенетического и онтогенетического развитня ориентации птиц, где навигация рассматривается как филогенетически более раннее явление, чем миграционная ориентация. Используя при отправлении ориентацию по признакам местности и возможность компасной ориентации, на обратном пути птицы предположительно ориентируются по компасу и на этой основе уэнают местность. Благодаря этому на местности - " мозаичная карта " для ориентации внутри домовой территории. Сопоставляя такие же механизмы с факторами обладающими естественньми градиентами, мы получаем в определенной системе координат " навигационную карту ", позволяющую птицам возвращаться домой из незнакомых территорий при экстраполяциях их перелетов. К тому же у перелетных птиц предполагается наличие наследственно закрепленной информации о направлении и протяженности их перелета, причем, направление закреплено в генотипе, в то время как система компасной ориентации использыется для домовой территории.
We measured values for natural remanent magnetization (NRM) and isothermal-induced remanent magnetization (IRM) in the head and neck for relatively large samples of eight bird species, and smaller samples of 13 additional species. Significant differences were found in mean NRM values among species; values ranged from $3.090\times 10^{-12}\ {\rm T}$ (tesla) for the Carolina Wren (Thryothorus ludovicianus) to $38.069\times 10^{-12}\ {\rm T}$ for the Northern Bobwhite (Colinus virginianus). Mean IRM values ranged from $337.6\times 10^{-12}\ {\rm T}$ in Chimney Swifts (Chaetura pelagica) to $1,889.1\times 10^{-12}\ {\rm T}$ in European Starlings (Stutnus vulgaris), with intraspecific variation being notably high. For two European Starlings and a Common Grackle (Quiscalus quiscula), about three-fourths of the IRM was located in the head and one-fourth in the neck; heads of two Northern Bobwhites contained an even greater proportion of the IRM. In general, the direction of the ferromagnetic material varied substantially among individuals within species. No significant differences were found in mean-vector directions among species. Linear regressions of NRM and IRM values on the logs of mean body mass indicate that the intensity of magnetism is related to species size. Insectivores, which also were the smallest species, had lower NRM and IRM values than found for omnivores sampled. Characteristic demagnetization-remagnetization curves suggest that most of the magnetic materials are interacting single-domain or pseudosingle-domain grains of magnetite. Three species may contain some superparamagnetic material. No differences were found between migratory and nonmigratory species with respect to the amount of remanent magnetism, or the extent of intraspecific variability in orientation direction of NRM.
Site fidelity to breeding and wintering grounds, and even stopover sites, suggests that passerines are capable of accurate navigation during their annual migrations. Geolocator-based studies are beginning to demonstrate precise population-specific migratory routes and even some interannual consistency in individual routes. Displacement studies of birds have shown that at least adult birds are capable of goal-oriented movements, likely involving some type of map or geographic position system. In contrast, juveniles on their first migration use a clock-and-compass orientation strategy, with limited knowledge about locations along their migratory routes. Positioning information could come from a variety of cues including visual, olfactory, acoustic, and geomagnetic sources. How information from these systems is integrated and used for avian navigation has yet to be fully articulated. In this review, we (1) define geographic positioning and distinguish the types of navigational strategies that birds could use for orientation, (2) describe sensory cues available to birds for geographic positioning, (3) review the evidence for geographic positioning in birds and methods used to collect that evidence, and (4) discuss ways ornithologists, particularly field ornithologists, can contribute to and advance our knowledge of the navigational abilities of birds. Few studies of avian orientation and navigation mechanisms have been conducted in the Western Hemisphere. To fully understand migratory systems in the Western Hemisphere and develop better conservation policies, information about the orientation and navigation mechanisms used by specific species needs to be integrated with other aspects of their migration ecology and biology.
Several studies have shown that experienced night-migratory songbirds can determine their position, but it has remained a mystery which cues and sensory mechanisms they use, in particular, those used to determine longitude (east-west position). One potential solution would be to use a magnetic map or signpost mechanism like the one documented in sea turtles. Night-migratory songbirds have a magnetic compass in their eyes and a second magnetic sense with unknown biological function involving the ophthalmic branch of the trigeminal nerve (V1). Could V1 be involved in determining east-west position? We displaced 57 Eurasian reed warblers (Acrocephalus scirpaceus) with or without sectioned V1. Sham operated birds corrected their orientation towards the breeding area after displacement like the untreated controls did. In contrast, V1-sectioned birds did not correct for the displacement. They oriented in the same direction after the displacement as they had done at the capture site. Thus, an intact ophthalmic branch of the trigeminal nerve is necessary for detecting the 1,000 km eastward displacement in this night-migratory songbird. Our results suggest that V1 carries map-related information used in a large-scale map or signpost sense that the reed warblers needed to determine their approximate geographical position and/or an east-west coordinate.
Pusimos a prueba dos métodos de reintroducción de individuos cautivos de la especie en peligro Athene cunicularia en Saskatchewan, Canadá. La primera técnica involucró la liberación de parejas adultas criadas en cautiverio. Doce de 26 parejas permanecieron juntas usando esta técnica, mientras que 6 individuos formaron parejas con individuos silvestres. El éxito en la formación de parejas y el éxito de nidificación fueron bajos cuando los individuos cautivos permanecieron en el sitio de liberación por sólo 3 días antes de ser liberados; el éxito incrementó cuando los individuos permanecieron por 5 días o hasta el inicio de la eclosión. Al menos el 19% de los adultos liberados murieron durante la temporada reproductiva, comparado con sólo el 3.7% de los individuos silvestres. Al menos cinco adultos liberados no migraron. Ninguno de los adultos cautivos que fueron liberados regresó al sitio de estudio en años subsecuentes, mientras que el 19% de los individuos silvestres que fueron anillados regresaron durante el mismo periodo. Una de las 62 crías producidas por las parejas liberadas regresó a criar en años subsecuentes; esta tasa de reclutamiento no fue diferente a la de crías producidas por adultos silvestres. La segunda técnica de liberación involucró el dar en adopción pichones eclosionados en cautiverio a parejas silvestres con nidos. Dimos en adopción 54 juveniles de tres diferentes edades. Los pichones fueron aceptados por las parejas silvestres. El crecimiento, sobrevivencia y comportamiento de los pichones adoptados no fue diferente al de sus hermanos silvestres. Nuestros resultados sugieren que los adultos criados en cautiverio pueden criar exitosamente en la naturaleza, pero permanecen dudas acerca de su habilidad para migrar exitosamente. Dar polluelos en adopción a parejas silvestres mostró cierto éxito, pero también tuvo algunas limitaciones.
Animals navigate over a range of distances, but it has been the global navi-gation of species migrating among spatially restricted, seasonal homes separated by thousands of kilometers that continues to defy a thorough mechanistic expla-nation. We survey the navigational behavior of migratory salmon, whales, sea turtles, and birds, as well as dispersing monarch butterflies, to promote the idea that an explicitly comparative approach to global navigation can provide insight into the evolution and properties of navigational mechanisms. The navigational abilities of migrant birds and sea turtles are used to illustrate the concepts of true navigation and vector navigation, leading us to consider the selective forc-es that might shape the evolution of navigational mechanisms. We propose that different navigational mechanisms, with different scales of accuracy, are likely employed during the course of migration. Furthermore, superficially similar glo-bal migratory behavior in different taxonomic groups is likely characterized by different sensory, representational and neural mechanisms reflective of group-specific adaptation to the physical properties of a migratory environment.
Many aspects of migration have been studied extensively, but little is known of how environmental conditions influence the behaviors displayed by migrants. Field studies suggest that such environmental factors as atmospheric conditions, nocturnal illumination, and food availability can affect migratory activity. We used 24 hr locomotor activity records and specific behaviors displayed by captive migrants to determine how nocturnal illumination and food restriction altered the migratory behavior of Gambel's White-crowned Sparrows (Zonotrichia leucophrys gambelii). Our results indicated that nocturnal locomotor activity was enhanced with increased nocturnal illumination at the source from 0 to 9 lux, even though the intensity of illumination that reached the birds remained <1 lux. Food deprivation had little effect on migratory restlessness per se, but resulted in increased locomotor activity during daylight hours and behaviors associated with attempts to escape from the cage. Thus, we suggest that migrants respond to variations in environmental conditions by altering both day and nighttime behaviors. Plasticity of behavior would allow free-living migrants to respond quickly to changes in the environment, thus enhancing the likelihood of successfully reaching their destinations.
Das nächtliche Zugverhalten verschiedener Zonotrichia-Arten wurde im beschriebenen 8-Stangen-Orientierungskäfig automatisch registriert. Die Tiere blieben einige Tage bis mehrere Monate darin. Ein Index für Gesamtaktivität, mittleres Azimut (Richtung) und Richtungsbevorzugung (Stärke der Orientierung) wurde für jede der 4198 Vogelstunden über den ganzen Lunarzyklus berechnet. Die nächtliche Orientierung wurde auf verschiedene Umweltvariable analysiert, speziell auf Azimut des Mondes und seiner Höhe über dem Horizont.
Many migratory birds show philopatry, i.e. they regularly breed and winter at the same sites. The routes taken by migrants are adjusted to the geographical and ecological conditions between breeding and wintering areas, often resulting in indirect paths. Young birds on their first migration face the task of reaching the as yet unknown population-specific winter quarters with the help of innate information. Large-scale displacement experiments with migrants and cage experiments with hand-raised birds revealed that this innate information is given as direction and distance, with the distance controlled by an endogenous time program that determines amount and temporal distribution of migratory activity. Both, migratory activity and direction — or, in the case of indirect routes, a sequence of directions — are genetically transmitted from one generation to the next.
Birds use two reference systems to convert innate directional information into an actual flying course: celestial rotation and the geomagnetic field. Celestial rotation produces a reference direction opposite from its center, which is obtained by observing the diurnal and/or the nocturnal sky. This reference can be used to establish a star compass, not only utilizing the natural, but also artificial “stars”, provided the birds can observe these “stars” rotating. However, with only stars available, migrants that normally prefer southwesterly courses show southerly tendencies, apparently unable to convert the population-specific components of their migratory direction. Birds raised with only magnetic cues available, in contrast, are well oriented in their population-specific migratory direction, except in areas with steep inclination; here, the magnetic field provides only an axis, and birds also need celestial rotation for unimodal orientation. As the birds' magnetic compass is an inclination compass, migrants of the northern and southern hemisphere may use the same migratory program, starting out “equatorwards” in autumn.
During the premigratory period, both reference systems interact to determine the migratory course. If North indicated by celestial rotation and magnetic North diverge, celestial rotation proves dominant, resulting in a changed magnetic compass course. However, celestial rotation does not simply override the magnetic course. In the natural situation, celestial rotation provides only the reference direction “opposite from the center of rotation”, corresponding to geographic South, which can be substituted by magnetic South if birds have no access to celestial cues. Population-specific deviations from South seem to be coded only with respect to the magnetic field and are then added to the reference direction, resulting in the population-specific migratory course. These processes are interrupted if the sky is made to rotate in the reverse direction. The reasons for using two reference systems may lie in the fact that at higher latitudes, the magnetic field is strongly affected by secular variations, while celestial rotation reliably provides geographic South. At the same time, the magnetic field, being directly perceivable, may be better suited for indicating angular deviations.
During migration itself, the relationship between the two reference systems changes, with the magnetic field becoming dominant. In case of conflict, celestial cues are recalibrated according to magnetic North. The reasons for this shift in dominance may lie in celestial rotation ceasing to play a role. The sky changes its appearance as the birds progress, and the new stars are calibrated with the help of the geomagnetic field which becomes a reliable source of directional information at temperate and lower latitudes.
Many birds change direction during migration. Their second compass course is coded with respect to the magnetic field. The conversion of the respective innate information appears to take place en route; a possible role of celestial rotation has not yet been analysed. In Garden Warblers and Yellow-faced Honeyeaters, the shift in direction can take place under the control of the endogenous time program alone; Pied Flycatchers, in contrast, require magnetic conditions of the region where the shift normally takes place. At the magnetic equator, birds must reverse their course with respect to their magnetic compass from equatorwards to polewards in order to continue southwards. Here, the field of the equator with its horizontal field lines serves as trigger. At the equator itself, where the magnetic compass becomes bimodal, birds may rely on celestial cues.
The innate migratory program enables young birds to reach their general wintering area. The program becomes flexible at the end and allows them to look around for a suitable site to spend the winter. This becomes their winter “home” to which they return upon displacement. For the return migration to the breeding area and any later migrations, migratory birds can make use of experience obtained during earlier travels. The migratory program still provides them with directional information; however, navigational processes based on site-specific information dominate over the innate mechanisms. Many young birds undertake extended exploratory flights before they leave for migration, thus establishing a “map” of their future breeding area. As a consequence, they return to the normal breeding area after displacement. Adult birds must be expected to choose their migration route by mechanisms of true navigation, thus avoiding unfavorable areas and revisiting good refueling sites, at the same time becoming less vulnerable to wind drift and similar phenomena. Details of these navigation processes are not known, as they have escaped experimental analysis so far.
The dominant role of true navigation, which replaces the innate program, represents a parallel to homing, where birds also rely on mechanisms of true navigation as soon as these become available.
Nowadays few people consider finding their way in unfamiliar areas a problem as a GPS (Global Positioning System) combined with some simple map software can easily tell you how to get from A to B. Although this opportunity has only become available during the last decade, recent experiments show that long-distance migrating animals had already solved this problem. Even after displacement over thousands of kilometres to previously unknown areas, experienced but not first time migrant birds quickly adjust their course toward their destination, proving the existence of an experience-based GPS in these birds. Determining latitude is a relatively simple task, even for humans, whereas longitude poses much larger problems. Birds and other animals however have found a way to achieve this, although we do not yet know how. Possible ways of determining longitude includes using celestial cues in combination with an internal clock, geomagnetic cues such as magnetic intensity or perhaps even olfactory cues. Presently, there is not enough evidence to rule out any of these, and years of studying birds in a laboratory setting have yielded partly contradictory results. We suggest that a concerted effort, where the study of animals in a natural setting goes hand-in-hand with lab-based study, may be necessary to fully understand the mechanism underlying the long-distance navigation system of birds. As such, researchers must remain receptive to alternative interpretations and bear in mind that animal navigation may not necessarily be similar to the human system, and that we know from many years of investigation of long-distance navigation in birds that at least some birds do have a GPS - but we are uncertain how it works.
Our present understanding of orientation behaviour in birds is based on a broad array of observational, experimental and analytical (statistical) techniques, which are briefly reviewed here. As an extremely productive model the homing behaviour of pigeons has allowed especially diverse experimental manipulations documenting the involvement of magnetic, visual and olfactory cues in orientation. Work with migratory birds has profited greatly from the design of several kinds of orientation cages, now commonly used, and from hand-rearing test birds under controlled conditions. Free-flying birds, especially on long-distance migration, are still least amenable to study, but radio transmitter technology is providing important new opportunities in this respect. In general, the most valuable studies have been those involving the ontogenetic development of orientation, and those combining several methods of investigation. Some suggestions for further experiments are made.