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Introduction
Skills and Expertise
Publications
Publications (91)
Background
Populations of vultures in Africa have experienced a rapid decline over recent decades, with some species suffering losses of more than 90%. Various forms of human pressures have been identified as the causes of this decline. However, very little is known about the complex interaction between cultural practises, traditional medicine and...
Breeding habitat loss and depletion of genetic diversity can have critically negative impacts on species, and especially so for habitat specialists. The Aquatic Warbler Acrocephalus paludicola is a threatened European songbird that breeds in fens, which have been lost and fragmented over centuries. We used microsatellite loci to perform a spatial a...
A number of vulture species were ubiquitous in undisturbed West African savannahs. However, in recent decades most species have declined rapidly and some are now at the brink of extinction. For some species, large protected areas are their last strongholds, but even there pronounced declines have become obvious in recent years. However, we lack eve...
In migratory birds, constraints due to breeding are relaxed during the non-breeding season and thus, social behaviours and spatial associations are potentially more directly coupled to food resources and habitats. Use of space and territorial behaviour has rarely been studied in Afro-Palearctic migrants. Variation in strategies could exist among sp...
Identifying the fate of birds’ nests and the causes of breeding failure is often crucial for the development of conservation strategies for threatened species. However, collecting these data by repeatedly visiting nests might itself contribute to nest failure or bias. To solve this dilemma, automatic cameras have increasingly been used as a time-ef...
Aim
To investigate the ecological relationship between breeding and wintering in specialist and generalist long‐distance migratory species, and the links between densities and range sizes.
Location
Denmark, Senegal and Ghana.
Methods
We use radio tracking to study spatial behavior and habitat use in three morphologically and ecologically similar...
Hatching success is a key parameter for the evaluation of management activities for endangered bird species. Camera traps allow permanent monitoring of clutches and reduce the need for disturbance at the nest. We have been using camera traps since 2013 to monitor the breeding success and causes of failure of nests of the black-tailed godwit (Limosa...
Birds that are long-distance migrants partition their annual cycle among a number of locations over a large spatial range. The conservation of these species is particularly complex because it requires attention to a number of different and distant habitats based on knowledge of migratory phenology, routes and staging areas. In the case of the globa...
The Blackcap Sylvia atricapilla is a model species for the evolution of bird migration in a time of global change. However, many assumptions about putative changes to their migratory paths have not been verified because, until recently, it has not been possible to track individual small passerines throughout the entire migration cycle. With the rec...
The Black-tailed Godwit Limosa limosa is "critically endangered" in Germany and "endangered" in Schleswig-Holstein. The aim of the EU LIFE project LIFE-Limosa is to stabilize its remaining core-populations in Schleswig-Holstein by increasing the reproductive success. The aim of this study is to report breeding success of Black-tailed Godwits, and t...
The most studied ecogeographic rule is Bergmann's rule, but aspects of the original paper are often presented incorrectly even though Bergmann (1847) is explicitly cited. The goal of this paper is to 1) summarize the contents of Bergmann's paper, supported by direct translations, and 2) to discuss the main issues surrounding Bergmann's rule based o...
Over decades it has been unclear how individual migratory songbirds cross large ecological barriers such as seas or deserts. By deploying light-level geolocators on four songbird species weighing only about 12 g, we found that these otherwise mainly nocturnal migrants seem to regularly extend their nocturnal flights into the day when crossing the S...
In migratory birds, morphological adaptations for efficient migratory flight often oppose morphological adaptations for efficient behavior during resident periods. This includes adaptations in wing shape for either flying long distances or foraging in the vegetation and in climate-driven variation of body size. In addition, the timing of migratory...
Table S1. Morphometry of nightingales (Luscinia m. megarynchos) across its distribution range.
Figure S1. Longitudinal pattern of migration distance and four environmental factors at specific breeding sites of local populations used in the study.
Changes in morphology have been postulated as one of the responses of animals to global warming, with increasing ambient temperatures leading to decreasing body size. However, the results of previous studies are inconsistent. Problems related to the analyses of trends in body size may be related to the short-term nature of data sets, to the selecti...
Declining body size has been suggested to be a response of animals to global warming, but analyses of time series have led to contradictory results. One problem is that each trait related to body size may vary in response to factors other than temperature and independently of size. We analyse trends of three morphological traits of a passerine bird...
Weather affects the demography of animals and thus climate change will cause local changes in demographic rates. In birds numerous studies have correlated demographic factors with weather but few of those examined variation in the impacts of weather in different seasons and, in the case of migrants, in different regions. Using capture-recapture mod...
The globally-threatened Aquatic Warbler (Acrocephalus paludicola) breeds in Europe and spends the northern winter in sub-Saharan West Africa. We attached 30 geolocators to breeding birds in the central Ukraine in 2010. Three geolocators which collected data from the autumn migration were recovered in 2011. They revealed a previously-unknown migrati...
Wing and tail length measurements are important tools in ornithology. Amongst linear measurements, wing length has been considered to be the best indicator for body size for taxonomy and ecomorphology, as well as for studies about the impact of climate change on morphology. As feathers are dead tissue, abrasion will lead to a reduction in wing and...
We report the isolation and characterization of eleven microsatellite markers from the Aquatic Warbler (Acrocephalus paludicola) the only globally threatened passerine species in Europe. We tested the markers in 23 samples of the species collected in
the Biebrza marshes, Poland, between 1990 and 1997. All markers were polymorphic, with 2–16 alleles...
Knowledge of population-specific non-breeding areas in sub-Saharan Africa for the globally threatened Aquatic Warbler Acrocephalus paludicola is paramount for the implementation of successful conservation strategies that consider the species' entire annual range. This may be the case especially for declining marginal populations. Here we report on...
The Aquatic Warbler Acrocephalus paludicola (AW) is the only globally threatened passerine species of continental Europe. The global population decreased by>90% during
the 20th century. AWs breed in Palaearctic fen mires and sedge meadows and spend the non-breeding season in sub-Saharan Africa,
but until 2007 no regular wintering site had been iden...
The many definitions of Bergmann's rule have resulted in confusion and debate over how and in what organisms to test the original rule. Watt et al. published a paper in 2010, based directly on Bergmann's original paper, in the hopes of clarifying the rule and presenting direct translations to resolve uncertainties. Recently, Olalla-Tárraga has crit...
Charles Darwin is well known for his studies on the expression of emotions in animals and humans and as founding father of
the concept of sexual selection. Yet it is commonly believed that the various arguments Darwin developed about behavior were
usually illustrated only by anecdotes and observations recounted by explorers, naturalists, or zookeep...
Twice a year, songbirds breeding in the Western Palaearctic cross the largest desert of the world, the Sahara, to reach their
African winter quarters. Recently, a radar study quantified this migration and demonstrated that almost all passerines cross
the western Sahara with an intermittent strategy, i.e. they fly during the night and rest during th...
Knowing the amount of body mass that migrants can lose is essential for the estimation of potential flight ranges, assessing the importance of stopover sites or modelling migration strategies. ‘Lean’ body mass, (the mass without fat stores) is often used to describe the limit of body‐mass loss but birds also use protein as fuel for flight. The mean...
The strategy of migrants crossing the Sahara desert has been the subject of debate, but recent evidence from radar studies
has confirmed that most passerines use an intermittent migration strategy. The latter has also been suggested from previous
studies in oases during autumn migration. It was found that migrants with relatively high fuel loads re...
Sex determination of birds is important for many ecological studies but is often difficult in species with monomorphic plumage.
Morphology often provides a possibility for sex determination, but the characters need to be verified. We tested whether five
passerine species can be sexed according to standard morphological measurements applying a forwa...
Identifying the staging areas of Aquatic Warblers Acrocephalus paludicola in the nonbreeding
season is a high priority for the conservation of the species. After a first
expedition in 2008 a second expedition to search for this species was undertaken in
Diawling National Park, south-western Mauritania from 23 – 27 January 2010. No
Aquatic Warblers...
Capsule Migrant Willow Warblers occupy more woodland types and occur at higher densities than ecologically‐similar resident Afrotropical warblers.Aims To compare population densities of Willow Warblers and eremomelas in adjacent acacia, mopane and miombo woodlands, and assess the abundance of potential invertebrate prey in each habitat type, in ord...
The science behind ecology has been contested for years, partially because of the misuse and misrepresentation of concepts within ecology. This paper discusses the use of Bergmann's rule, a fundamental rule of biogeography. The rule was proposed by Carl Bergmann in 1847 and was published only in German; therefore, the majority of researchers have r...
Fat is the prime energy source for birds during prolonged exercise, but protein is also catabolized. Estimates of the amount of catabolizable fat and protein (termed fat and protein fuel) are therefore important for studying energetics of birds. As fat and protein fuel can only be measured by sacrificing individuals or by use of technically complex...
Recent climate change has caused diverse ecological responses in plants and animals. However, relatively little is known about homeothermic animals’ ability to adapt to changing temperature regimes through changes in body size, in accordance with Bergmann’s rule. We used fluctuations in mean annual temperatures in south-west Germany since 1972 in o...
We use widely supported handbook data on annual fecundity (clutch size × annual number of normal broods) to obtain indications related to the relative costs of long-distance migration compared to lower levels of migratoriness. Our examples show that the yearly production of eggs in congeneric passerines of similar size from temperate Europe is lowe...
Both Western Olivaceous Warbler Hippolais opaca and Eastern Olivaceous Warbler Hl pallida, of the form reiseri, occur in Morocco.The distribution of Western Olivaceous Warbler in the northern parts of the country is well known. Eastern Olivaceous Warbler has been recorded from the southeastern parts of Morocco, but its status, range limits and the...
We infer from the literature that migratory habits of birds evolved in various phylogenetic lineages and biogeographical contexts, either after gradual range expansion into seasonal habitats, or due to environmental changes within established breeding ranges. Shifts of breeding ranges are the results of interactions between colonization due to disp...
We discuss alternatives to the recently predominating ideas (a) that bird migration evolved from low towards higher latitudes to capitalise on seasonally abundant resources allowing higher reproductive output, and (b) that migrant birds have their origin generally in southern tropical areas (southern-home theory). Different from this view, we sugge...
Studies of birds involving colour ringing can provide much detailed information concerning bird movements and behaviour without the need for recapture. However, a fundamental premise of colour ringing, and indeed all ringing studies, is that the rings applied should neither cause harm to the birds concerned nor alter their behaviour or survival. Co...
Records of interspecific agonistic behaviour of Palaearctic passerine migrants from their Afrotropical wintering grounds are rare. There are, however, no detailed observations from stopover sites where individuals might concentrate and depress resources that are critical for fat-depleted birds in times of high energy demand. We recorded intraspecif...
We approach the problem of the evolution of bird migration by asking whether migration evolves towards new breeding areas or towards survival areas in the non-breeding season. Thus, we avoid the ambiguity of the usually discussed "southern-home-theory" or "northern-home-theory". We argue that migration evolved in birds that spread to seasonal habit...
Birds on migration spend much more time on stopover sites to refuel for the next migration step than aloft, but empirical data on stopover duration are rare, especially for Palearctic trans-Sahara migrants whilst crossing the desert. Previous studies suggest that stopover duration of fat birds in oases is much shorter than that of lean birds. Durin...
Analyses of stopover parameters of migrating birds with Cormack–Jolly–Seber (CJS) capture–recapture models often suffer from
low precision due to sparse data sets. Low recapture rates result in low power to detect violations of the underlying assumptions
and factors influencing stopover behaviour. We studied stopover behaviour of Palearctic migrant...
Due to the problems of identifying the recently‐split Western Olivaceous Warbler Hippolais opaca and Eastern Olivaceous Warbler H pallida reiseri in the field, the migration phenology, passage routes and wintering areas of the two species remain unknown. Both species were mist‐netted regularly during autumn and spring migration on Mauritania and th...
Nectarivory of long-distance Palearctic migrants is known from Europe but there are few reports of nectar as a resource for migrants in Africa. Migrants feeding on nectar were regularly observed in the oasis of Ouadâne, a stopover site in the western Sahara, Mauritania, in spring 2003 and 2004. Migrant species observed consuming nectar were Eastern...
Previous ecological studies of Palearctic passerine migrants in Africa have claimed to reveal some general features with respect
to habitat use, foraging ecology and interspecific relationships with Afrotropical residents. In this review we discuss apparent
contradictions between earlier generalisations and more recent results from more detailed fi...
One of the main questions of former studies on the wintering ecology of long distance migrants is how migrants partition resources with residents in their winter quarters and to what extent competition between the two groups plays a role for the evolution of the present avian communities. Here, we summarize the results of our own studies from Ivory...
Des nouveaux sites de nidification de la Fauvette à lunettes Sylvia conspicillata ont
été trouvés dans la région d'Adrar en Mauritanie au printemps de 2004. Ceux-ci constituent la
première preuve de nidification pour le pays et les nidifications les plus méridionales en Afrique
continentale. Au moins quatre nichées ont été observées dans les oasis...
Recent research on the systematics of the genus Hippolais led to the proposal to split Olivaceous Warbler Hippolais pallida into Western Olivaceous Warbler H opaca and Eastern Olivaceous Warbler H pallida with the subspecies pallida, elaeica, laeneni and reiseri. Here, we present data on postnuptial primary moult in relation to age, for H p reiseri...
Some theories about moult strategies of Palaearctic passerine migrants assume that birds adapt timing of moult to environmental conditions such as rainfall on their African wintering grounds. Species wintering in the northern tropics should limit moult to the period shortly after their arrival at the end of the rainy season. Passerine migrants wint...
From March 1989 until May 1995 overall 675 hauls were performed using a commercial stow net vessel to get information concerning spatial and seasonal distribution, length frequency distribution, stock situation and migration patterns of lampreys in the Elbe estuary in northern Germany.2217 river lampreys (Lampetra fluviatilis) and 10 sea lampreys (...
Amongst several theories of speciation, sympatric speciation has been the most controversial but it is now widely accepted that populations can become reproductively isolated without being separated geographically. One problem with the acceptance of the theory of sympatric speciation, however, has been the lack of supporting empirical data and it i...
In bird migration systems, the question of coexistence and competition of migrants with residents in the nonbreeding season and their role in shaping the evolution of present avian communities is much debated. However, conclusions are often drawn in a speculative way. In the Palearctic-African bird migration system, many studies have addressed the...
In bird migration systems, the question of coexistence and competition of migrants with residents in the nonbreeding season and their role in shaping the evolution of present avian communities is much debated. However, conclusions are often drawn in a speculative way. In the Palearctic-African bird migration system, many studies have addressed the...
We investigated the habitat selected by two Palaearctic migrants (Pied Flycatcher, Ficeduh hypaleuca, Willow Warbler, Phylhscopus trochilus) in a patchy landscape in Ivory Coast and compared it with the habitat selection of Afrotropical species in the same foraging guilds. Transect counts were used to test the hypothesis that migrants use more open...
The wintering strategies of Pied Flycatchers Ficedula hypoleuca and Willow Warblers Phylloscopus trochilus in their West African winter quarters were compared. Pied Flycatchers arrived early in the season (September) and stayed in the study area throughout the winter. They were territorial and showed a high return rate. Intraspecific relationships...
Constant effort mist netting sites are widely used along the Palearctic-African migration system in areas north of the Sahara to collect standardised migration data. However, in sub-Saharan Africa such sites are scarce. We present data collected at a constant effort site which we ran once about every ten days in the northern Guinea savannah zone in...
A rocky area in Lamto, Ivory Coast, which is partly surrounded by plantations, was searched for nests of the White-necked Picathartes Picathartes
gymnocephala. A total of 34 nests was found of which 10 were only remnants, 12 old and 12 rather new. One nest contained two chicks. It is suggested that ecotourism might be a suitable means to help to pr...
Salewski, V. 2000. Microhabitat use and feeding strategies of the Pied Flycatcher and the Willow Warbler in their West-African winter quarters compared with resident species. Ostrich 71 (1 & 2): 191–193.Habitat choice, microhabitat and foraging behaviour of the palaearctic Pied Flycatcher and Willow Warbler are described in their West-African winte...
A rocky area in Lamto, Ivory Coast, which is partly surrounded by plantations, was searched for nests of the White-necked Picathartes Picathartesgymnocephala. A total of 34 nests was found of which 10 were only remnants, 12 old and 12 rather new. One nest contained two chicks. It is suggested that ecotourism might be a suitable means to help to pro...
Between spring 1994 and spring 1997 329 birds of 15 Palearctic passerine species and the Wryneck (Jynx torquilla) were ringed in the Comoe National Park, Ivory Coast. The species which were caught most frequently were Willow Warbler (Phylloscopus trochilus, n = 110), Pied Rycatcher (Ficedula hypoleuca, 94) and Melodious Warbler (Hippolais polyglotl...
The first record of the Petromyzontidae from the Black Sea region of Turkey was a new species, Iıımpetra lanceolaİa Kux & steiner, |972. lthıs not been found since. In this paper, a second record of lampreys from North-Eastern Turkey is reported, from a different locality and of an unidentified species. Kurzfassnng: Der erste Nachweis von Neunaugen...
2006: Mark -recapture -statistics for the estimation of survival rates and other parameters -theory and examples. Ber. Vogelwarte Hiddensee 17: 23-31. A precondition for establishing effective bird conservation strategies is the understanding of basic mechanisms of population growth. This can only be achieved if the specific role of main demographi...
The nature of the mechanisms that may structure ani-mal communities is much debated and the role of inter-specific competition in particular is difficult to detect in the field (Huston 1994). In many situations it is only possible to monitor putative mechanisms of niche par-titioning that might enable species to coexist. The role of the interspecif...
