Spatial and Temporal Variability in Migration of a Soaring Raptor Across Three Continents

Abstract

Disentangling individual-and population-level variation in migratory movements is necessary for understanding migration at the species level. However, very few studies have analyzed these patterns across large portions of species' distributions. We compiled a large telemetry dataset on the globally endangered Egyptian Vulture Neophron percnopterus (94 individuals, 188 completed migratory journeys), tracked across ∼70% of the species' global range, to analyze spatial and temporal variability of migratory movements within and among individuals and populations. We found high migratory connectivity at large spatial scales (i.e., different subpopulations showed little overlap in wintering areas), but very diffuse migratory connectivity within subpopulations, with wintering ranges up to 4,000 km apart for birds breeding in the same region and each subpopulation visiting up to 28 countries (44 in total). Additionally, Egyptian Phipps et al. Egyptian Vulture Migration Flexibility Vultures exhibited a high level of variability at the subpopulation level and flexibility at the individual level in basic migration parameters. Subpopulations differed significantly in travel distance and straightness of migratory movements, while differences in migration speed and duration differed as much between seasons and among individuals within subpopulations as between subpopulations. The total distances of the migrations completed by individuals from the Balkans and Caucasus were up to twice as long and less direct than those in Western Europe, and consequently were longer in duration, despite faster migration speeds. These differences appear to be largely attributable to more numerous and wider geographic barriers (water bodies) along the eastern flyway. We also found that adult spring migrations to Western Europe and the Balkans were longer and slower than fall migrations. We encourage further research to assess the underlying mechanisms for these differences and the extent to which environmental change could affect Egyptian Vulture movement ecology and population trends.

First record of Rufous-thighed Kite Harpagus diodon in Colombia

“…Nonetheless, the Colombian portion of this part of Amazonia has also yielded several recent novelties in avian distribution (Carantón Ayala et al 2016, Peña Alzate et al 2020, highlighting the need for further surveys and field work. Additional work with Rufous-thighed Kite could include the use of satellite tags or solar geolocators to analyse the movements of this austral migrant across Amazonia (Lees & Martin 2015, Winkler et al 2017, techniques which have proven efficient at tracking raptor movements elsewhere in the world (Phipps et al 2019). Such studies should include birds breeding in the Atlantic Forest of Brazil (Lees & Martin 2015), the Cerrado in eastern Bolivia, and Austral Yungas in Bolivia and Argentina (Areta & Juhant 2019).…”

Winter movement patterns of a globally endangered avian scavenger in south-western Europe

“…Therefore, a shift from a migratory behaviour to a sedentary one could have positive effects on the conservation status of the Egyptian Vulture in Europe in the long-term 77 . However, the continuous presence of some individuals in a given area implies that they are also subject to threats that are only faced during the breeding period for migratory conspecifics 38 , such as human disturbances and habitat alterations in roosting or nesting sites , collisions with wind farms and illegal poisoning 78 . Besides, the strong dependence on food resources provided by humans direct or indirectly by intensive livestock farming practices could increase poisoning risk 79 .…”

“…The European breeding population is estimated at around 3000–4700 pairs 37 . It is a migratory bird that abandons its European breeding areas between late August and February 38 . The species exhibits high migratory connectivity at large spatial scales, but very diffuse migratory connectivity within subpopulations, with wintering ranges up to 4000 km apart for birds breeding in the same region, and each subpopulation visiting up to 28 countries 38 .…”

“…It is a migratory bird that abandons its European breeding areas between late August and February 38 . The species exhibits high migratory connectivity at large spatial scales, but very diffuse migratory connectivity within subpopulations, with wintering ranges up to 4000 km apart for birds breeding in the same region, and each subpopulation visiting up to 28 countries 38 . European populations winter in sub-Saharan Africa and the Arabian Peninsula, with juveniles often remaining in the winter range for more than a year after their first migration 39 , 40 .…”

Dynamics of the energy seascape can explain intra-specific variations in sea-crossing behaviour of soaring birds

“…While their large wing area to body mass ratio makes soaring birds adapted to extract energy from uplifts, flapping flight, precisely because of the large wings, represents an expensive task [13, 14]. As such, various obligate soaring birds rely on traditional overland detours [15, 16], the cost of which is offset by their low energy consumption in thermal-soaring flight [17]. Most of the landbirds capable of thermal soaring are facultative soaring migrants.…”