Figure 4 - uploaded by Josh A Firth
Content may be subject to copyright.
Mixing index for successive gathering events after an attack event in the experimental condition (red dot-dashed line) and after the matched control event in the post-experimental control condition (solid blue line).: The bold line gives the fit of an exponential function to the mixing indices after all control events. The shaded area gives the 95% confidence interval for the estimated function for the control condition. Thin red and blue lines give the median values over all attack and control events. The horizontal line indicates the estimated mixing index for the first post-attack gathering event and the intersections between this line and the 95% CIs for the control condition were taken as the upper and lower estimates (dotted grey lines) for the time-effect that the attack had on the mixing index. On average, the distance between two consecutive gathering events equates to 6.5 minutes (392 s). Figures indicating the effect on the ‘blending’ and ‘change’ indices are provided in the online supplementary material.
Source publication
Nonlethal predator effects arise when individuals of a prey species adjust their behaviour due to the presence of predators. Non-lethal predator effects have been shown to affect social group structure and social behaviour as well as individual fitness of the prey. In this experimental study, we used model sparrowhawks to launch attacks on flocks o...
Context in source publication
Context 1
... RepoRts | 6:33476 | DOI: 10.1038/srep33476 (Fig. 4). Based on this, we estimate that each single model predator attack generates the same change as we would otherwise expect, under normal conditions, after between 18.5 and 25 gathering events; the same blending expected after between 22.3 and 34.6 gathering events, and the same mixing as expect after between 22 and 33 gathering events. ...
Similar publications
Animal behavior should optimize the difference between the energy they gain from prey and the energy they spend searching for prey. This is all the more critical for predators occupying the pelagic environment, as prey is sparse and patchily distributed. We theoretically derive two canonical swimming strategies for pelagic predators, that maximize...
Cemophora coccinea feed largely on the eggs of other reptiles and have been observed piercing through eggs that are too large to swallow whole; herein we describe five observations of C. coccinea inside newly deposited nests (i.e., nests deposited within the past 24 h) of the federally-threatened Caretta caretta (Loggerhead Sea Turtle) in a manner...
Toothed whales have evolved to live in extremely different habitats and yet they all rely strongly on echolocation for finding and catching prey. Such biosonar based foraging involves distinct phases of searching for, approaching, and capturing prey, where echolocating animals gradually adjust sonar output to actively shape the flow of sensory info...
Predator-prey interactions play important roles in ecological communities. Personality, consistent inter-individual differences in behaviour, of predators, prey or both are known to influence inter-specific interactions. An individual may also behave differently under the same situation and the level of such variability may differ between individua...
Citations
... Although human-induced mortality (illegal hunting or collisions with power lines) may in some cases be responsible for reducing survival rates to below unsustainable levels, predation is in fact the main source of mortality in the Little Bustard (Marcelino et al. 2018). However, the effects that predators have on this species may go beyond direct mortality given that the presence of predators may induce changes in bustards' behaviour (Lima 1998, Cresswell 2008, with additional indirect consequences on population dynamics (Cresswell 2011, Voelkl et al. 2016. Such indirect effects include birds being disturbed from feeding, resting, displaying or any other activity, or being forced to move, all of which will entail associated energy costs, unexpected risk of mortality (collisions, exposure to other predators) and greater stress levels (Tarjuelo et al. 2015, Tarjuelo et al. 2022. ...
The Little Bustard Tetrax tetrax is an endangered steppe bird whose last remaining breeding populations in Catalonia (NW Spain) are located in the Lleida plains. Although the decline in this population is mainly associated with habitat loss and degradation due to agricultural intensification and urban encroachment, the proliferation of predators, some favoured by hu- mans, may also be having negative effects on this population, either through direct predation or indirect effects on behaviour and survival. Here, we describe the type of behavioural response exhibited by Little Bustards during the display season when they encounter a potential avian predator and discuss the possible indirect effects of these interactions. During counts carried out in the springs of 2010–2022 in three Special Protection Areas in the Lleida plains, 88 encounters between Little Bustards and eight species of avian predators were recorded. Among them, the Western Marsh Harrier Circus aeruginosus, Montagu’s Harrier C. pygargus and the Yellow-legged Gull Larus michahellis were the most frequent species involved in these encounters, although only the Yellow-legged Gull conducted deliberate attacks in a consistent way. Irrespective of the predator or its attitude, most encounters resulted in the Little Bustard being flushed. The number of encounters were higher at the beginning of the mating season, which may prevent Little Bustards from settling in otherwise suitable areas of habitat. The flushing of the bustards may increase the risk of collision with power lines and reduce mating success. Since the number of encounters between Yellow-legged Gulls and Little Bustards seems to have increased in recent years in the study area, we believe that there is a need to conduct further studies to understand how these interactions affect the population dynamics and conservation of this endangered species.
... Not only do they feed on eggs and chicks, but the presence of predators also limits the parental activity required for reproduction. In fact, many studies have reported on changes in prey species caused by predators [26][27][28] . In addition, it is often observed in nature that various birds protect their nests by establishing species of predators as neighbors who may pose a threat to their potential predators 29 . ...
We found that barn swallow (Hirundo rustica) breeding occurs within close proximity to humans. An evaluation of barn swallow breeding frequency and the breeding success rate of swallows at research sites, which were buildings inhabited by humans and buildings where humans had previously resided, was conducted in order to establish a relationship between the location of barn swallow nests and human habitation and activity frequency. The results demonstrated that barn swallows often breed in human-inhabited buildings. No significant relationship was observed between the wall material and the direction of the wall and the type of building, whereas a much higher proportion of the nests were located near doors with a high level of human movement. In addition, no significant correlation was observed between the location of the nest and the distance from potential resources (food, water etc.), however, a statistically significant relationship was observed between the frequency of human activity measured through the video camera and the number of nests located at a certain distance. The average number of offspring and the reproductive success rate were higher in nests located within close proximity to human activity compared to nests not located within close proximity to human activity, suggesting that the presence of humans had a positive effect on reproduction. This study show that barn swallow nesting occurs in locations where there is a human influence and humans provide implicit protection of swallows from predation, which has a significant impact on breeding.
... Predation has been shown to have profound lethal and non-lethal (Lima, 1998) impacts on prey individuals, affecting their behavior (Hulthén et al., 2021), phenotype development (Krams et al., 2020), fitness (Zanette and Clinchy, 2020;Allen et al., 2022), population structure and evolution (Yartsev, 2017;Dudeck et al., 2018). Prey individuals respond to predator acoustic, visual, chemical, and other cues, which improve the chances of prey to escape predator attacks (Lima, 1998;Preisser et al., 2005;Peckarsky et al., 2008;Voelkl et al., 2016;Zanette et al., 2019;. When developing under predation risk, prey individuals often grow smaller, more agile, less palatable, or more cryptic, conferring fitness benefits associated with a modified phenotype (Krams et al., 2016). ...
The development of high-throughput behavioral assays, where numerous individual animals can be analyzed in various experimental conditions, has facilitated the study of animal personality. Previous research showed that isogenic Drosophila melanogaster flies exhibit striking individual non-heritable locomotor handedness. The variability of this trait, i.e., the predictability of left-right turn biases, varies across genotypes and under the influence of neural activity in specific circuits. This suggests that the brain can dynamically regulate the extent of animal personality. It has been recently shown that predators can induce changes in prey phenotypes via lethal or non-lethal effects affecting the serotonergic signaling system. In this study, we tested whether fruit flies grown with predators exhibit higher variability/lower predictability in their turning behavior and higher survival than those grown with no predators in their environment. We confirmed these predictions and found that both effects were blocked when flies were fed an inhibitor (αMW) of serotonin synthesis. The results of this study demonstrate a negative association between the unpredictability of turning behavior of fruit flies and the hunting success of their predators. We also show that the neurotransmitter serotonin controls predator-induced changes in the turning variability of fruit flies, regulating the dynamic control of behavioral predictability.
... Overall, the results of this study demonstrate a higher pair formation among individual birds in a flock after they were fed by children in pairs than after they were fed by single children. These results are in agreement with an earlier work that demonstrated that non-predatory disturbances of the flocks of white tits alter the composition of the avian population by increasing the number of potential interaction partners over the following couple of hours of foraging (Voelkl, Firth, and Sheldon 2016). It is uncertain, however, what factors exactly are responsible for the consistently increased pairing rate when the observers fed the flocks in pairs. ...
The drives of inter-individual relationships within avian social groups are largely unexplored and relatively poorly understood, including how social landscapes affect the decisions of individuals within these groups. On a modest level, this study undertakes to expand this knowledge with an ornithological observation of temporary groupings among multiple aquatic species in response to the pairing of birdwatchers. More ambitiously, the study presumes the analogy between the social response of an avian community and the subliminal response of the human psyche to spatial stimuli. The number of bird pairs forming in flocks, coverts and rafts was consistently higher when the birds interacted with children teamed up in pairs than when solitary children interacted with the birds. Inadvertent social cues consequential to the extended duration of the focus, vigilance stimulation and subliminal messages affecting the neurological pathways in the brain and the social dynamics pertaining to proxemics are discussed as potential causes of this effect. Lastly, the structure of the paper mimics the lifetime of inventive ideas, which originate from a chaos of amorphous thought, then crystallize into a clarity of logical concepts open to elaboration, and eventually disperse into a similar semantic clutter as that from which they were born.
... Finally, the precise costs and benefits of being a leader or follower could not be ascertained in this study. For example, precise monitoring of predation risk is difficult with this set-up (but see Voelkl et al. (2016) for findings on predation dynamics in a separate experiment). Further experimental (in captivity) and observational (in the wild) studies are necessary to uncover and quantify the relative costs of leadership (Ioannou et al. 2019). ...
Collective behaviors are typical for many social species and can have fitness benefits for participating individuals. To maximize the benefits obtained from group living, individuals must coordinate their behaviors to some extent. What are the mechanisms that make certain individuals more likely to initiate collective behaviors, for example, by taking a risk to initially access a resource (i.e., to act as “leaders”)? Here, we examine leading behavior in a natural population of great tits and blue tits. We use automated feeding stations to monitor the feeder visits of tagged individuals within mixed-species flocks, with a small cost (waiting < 2 s) associated with the initial unlocking of the feeder. We find that great tits, males, and individuals with high activity levels were more likely to be leading in each of their feeder visits. Using a null model approach, we demonstrate that the effects of sex and activity on passive leading behavior can be explained by patterns of spatial and temporal occurrence. In other words, these effects can be explained by the times and locations of when individuals visit rather than the actual order of arrival. Hence, an analysis of the causes of leading behavior is needed to separate the effects of different processes. We highlight the importance of understanding the mechanisms behind leading behavior and discuss directions for future experimental work to gain a better understanding of the causes of leadership in natural populations.
Significance statement
Many species are social and engage in collective behaviors. To benefit from group actions, individuals need to fulfill different roles. Here, we examine leading behavior during feeding events; who feeds first when birds arrive at a resource? In mixed-species flocks of passerines, great tits (the larger and more dominant species), males, and individuals with higher levels of activity lead more often than blue tits, females, and individuals with lower levels of activity. While the species effect remains even when we control for the locations and dates of individual feeder visits, the effects of sex and activity are dependent on when and where birds choose to feed.
... For great tits, perceived predation risk can negatively affect weight gain and fat reserves, providing particularly compelling evidence for the predation-starvation tradeoff in songbirds [114,115]. Nonlethal effects can also alter mixed species flock composition: in winter foraging flocks of tit species (Family Paridae), perceived predation risk causes high turnover at foraging sites and in turn disrupts foraging success and stability of the group [116]. In combination, these non-lethal effects can result in overall population declines due to reduced survival and/ or reproduction [109]. ...
... This could be achieved, for instance, by the use of a moving predator model that is not visible continuously (see e.g. Gentle & Gosler, 2001, Voelkl et al., 2016, secondary predator cues such as scent, pellets or faeces (Andreasson et al. 2019) or predator vocalizations (Zanette et al. 2011;Santema et al. 2019). ...
Leaving the nest is a key transition in the life of altricial birds, whereby fledging decisions should depend on multiple factors, including the risk of predation. High postfledging predation risk may favour fledging at a more advanced stage of development, if more developed fledglings are better at escaping predation, or together with others. While comparative studies have highlighted the role of predation risk for between-species variation in the timing of fledging, drivers of within-species variation in fledging behaviour remain largely unknown. We presented owl models near blue tit, Cyanistes caeruleus, nests during the first half of the day throughout the fledging period to simulate an increased risk of postfledging predation. Using an automated monitoring system, we then recorded the precise fledging times of 595 nestlings from 105 nests (52 predator-treated, 53 control nests). Contrary to our predictions, the predator presentations did not affect the age at which nestlings fledged, the time of day of fledging or other aspects of fledging behaviour. The tendency to fledge together with siblings was affected, but the effect was in the opposite direction to that expected, with nestlings exposed to the predator treatment being more likely to fledge alone. Parents visited predator-treated nests less often, but this effect diminished over the course of the morning. We suggest several explanations for why the behavioural responses to the predation risk manipulation were generally limited.
... We used a Gaussian Mixture Model, which uses machine learning algorithms to identify gathering events (Psorakis et al. 2012(Psorakis et al. , 2015 implemented using the R package asnipe, Farine 2013, Supplementary Materials). This method has been used to infer flock membership and association patterns in birds with similar ecology (e.g., Voelkl et al. 2016;Evans and Morand-Ferron 2019). All birds detected during the same gathering events were considered to be in the same foraging flock. ...
Daily foraging activity of small wintering birds is classically thought to be driven by the need to gather enough energy reserves to survive each night. A separate line of research has shown that sociality is a major driver in winter foraging activities in many species. Here, we used wintering birds as a study system to move toward an integrative understanding of the influence of energy requirements and sociality on foraging ecology. We used RFID-enabled feeders in Lincoln, Nebraska, USA in January–March 2019 to measure foraging activity in two species (downy woodpeckers, Dryobates pubescens, and white-breasted nuthatches, Sitta carolinensis). We analyzed the relationship between overnight temperature and morning foraging activity and found that lowest overnight temperature was weakly correlated with morning visitation at feeders. We then used a network approach to ask if flock associations explain similarity in birds’ foraging activity. In both species, individuals with stronger associations in a social network were more likely to share similar feeder activity, and an index of social partners’ activity explained foraging activity better than overnight temperature. This brings forth new questions about the interplay between individual response to temperature and social factors in shaping how small animals cope with harsh winter conditions.
... Eurasian sparrowhawks (A. nisus) are a primary cause of mortality among tits in Wytham Woods [38], and in previous experiments, great tits and blue tits have been shown to react to such models as they would live predators [39,40]. The model was a plastic bird that was hand painted to closely resemble a sparrowhawk and was approximately the size of an adult male (length 350 mm, wingspan 560 mm). ...
... The model was a plastic bird that was hand painted to closely resemble a sparrowhawk and was approximately the size of an adult male (length 350 mm, wingspan 560 mm). This model was also used in previous predator exposure experiments conducted using this population [40]. The openings of both boxes had plastic curtains such that the model was not visible when inside the box. ...
In many species, individuals gather information about their environment both through direct experience and through information obtained from others. Social learning, or the acquisition of information from others, can occur both within and between species and may facilitate the rapid spread of antipredator behaviour. Within birds, acoustic signals are frequently used to alert others to the presence of predators, and individuals can quickly learn to associate novel acoustic cues with predation risk. However, few studies have addressed whether such learning occurs only though direct experience or whether it has a social component, nor whether such learning can occur between species. We investigate these questions in two sympatric species of Parids: blue tits (Cyanistes caeruleus) and great tits (Parus major). Using playbacks of unfamiliar bird vocalizations paired with a predator model in a controlled aviary setting, we find that blue tits can learn to associate a novel sound with predation risk via direct experience, and that antipredator response to the sound can be socially transmitted to heterospecific observers, despite lack of first-hand experience. Our results suggest that social learning of acoustic cues can occur between species. Such interspecific social information transmission may help to mediate the formation of mixed-species aggregations.
... All locally-born individuals are ringed as nestlings, and therefore their exact age is known. Birds born outside the woodland (immigrants) were aged when they were first trapped, either during the breeding season or as part of the large-scale ringing effort that takes place each winter (Voelkl et al. 2016). This was done using plumage characteristics (Svensson 1992); birds with first-year plumage are classified as yearlings (in their first year of life) and individuals first caught with adult plumage are assigned an estimated age of 2 years ). ...
An individual’s fitness is not only influenced by its own phenotype, but by the phenotypes of interacting conspecifics. This is likely to be particularly true when considering fitness gains and losses caused by extrapair matings, as they depend directly on the social environment. While previous work has explored effects of dyadic interactions, limited understanding exists regarding how group-level characteristics of the social environment affect extrapair paternity (EPP) and cuckoldry. We use a wild population of great tits (Parus major) to examine how, in addition to the phenotypes of focal parents, two neighborhood-level traits—age and personality composition—predict EPP and cuckoldry. We used the well-studied trait “exploration behavior” as a measure of the reactive-proactive personality axis. Because breeding pairs inhabit a continuous “social landscape,” we first established an ecologically relevant definition of a breeding “neighborhood” through genotyping parents and nestlings in a 51-ha patch of woodland and assessing the spatial predictors of EPP events. Using the observed decline in likelihood of EPP with increasing spatial separation between nests, we determined the relevant neighborhood boundaries, and thus the group phenotypic composition of an individual’s neighborhood, by calculating the point at which the likelihood of EPP became negligible. We found no evidence that “social environment” effects (i.e., neighborhood age or personality composition) influenced EPP or cuckoldry. We did, however, find that a female’s own age influenced the EPP of her social mate, with males paired to older females gaining more EPP, even when controlling for the social environment. These findings suggest that partner characteristics, rather than group phenotypic composition, influence mating activity patterns at the individual level.
