Abstract
AimTo investigate the ecological relationship between breeding and wintering in specialist and generalist long‐distance migratory species, and the links between densities and range sizes.LocationDenmark, Senegal and Ghana.MethodsWe use radio tracking to study spatial behavior and habitat use in three morphologically and ecologically similar and closely related Phylloscopus species on their widely separated breeding and wintering distributions. During wintering and breeding, willow warblers P. trochilus (winter: n = 9, breeding: n = 13), chiffchaffs P. collybita (n = 11, n = 7), and wood warblers P. sibilatrix (n = 17, n = 14) were tracked.ResultsWillow warblers P. trochilus increased home range sizes in winter, whereas it was similar in chiffchaffs P. collybita and wood warblers P. sibilatrix, in both seasons. Home ranges overlapped more in winter than in the breeding season. In winter, home range overlap was similar among species but larger overlap during breeding was indicated for willow warblers. Tree cover was unrelated to home range size but significantly higher in breeding than in winter in all species. However, whereas willow warblers and wood warblers maintained some degree of tall tree cover inside their home ranges in winter, chiffchaffs changed from more than 80% to <1% tree cover, indicating a niche shift.Main conclusionsIndividuals of all three species showed changes between breeding and wintering areas in spatial behavior and habitat availability, with larger overlap in winter. The differences in patterns were potentially related to being generalist (willow warbler) or specialist (chiffchaff and wood warbler). These ecological relationships are important for the conservation of migrants and for understanding the link between breeding and wintering distributions and ecology.
Highlights
Billions of birds move from breeding at higher to wintering at lower latitudes tracking resource abundance across seasons (Newton, 2008)
We focus on three morphologically and ecologically similar spe‐ cies of Phylloscopus warblers, willow warbler P. trochilus, chiffchaff P. collybita, and wood warbler P. sibilatrix (Figure 1)
Willow warblers were tracked at two sites in dry Savannah forest in Northern Ghana (9.09°N, 1.82°W), which is within the known wintering area of Danish breeding birds (Lerche‐ Jørgensen, Willemoes, Tøttrup, Snell, & Thorup, 2017), while wood warblers were tracked at a site in the Guinea forest‐savannah transi‐ tion zone in Southern Ghana (6.65°N, 0.7°W) in the same region as a Danish breeding bird wintering in Cotê d'Ivoire (Tøttrup, Pedersen, & Thorup, 2018)
Summary
Billions of birds move from breeding at higher to wintering at lower latitudes tracking resource abundance across seasons (Newton, 2008). Conservation of migrating species poses a spe‐ cial challenge as populations can potentially be adversely affected by habitat and climate change at any site used during the annual cycle (Runge, Martin, Possingham, Willis, & Fuller, 2014). It is vital for conservation of migrants to understand dependencies and link biology across seasons and sites (Runge et al, 2014). It is potentially constrained by having to be close to the nesting site and defend a territory (Gill, 1989) and such restrictions are released on the wintering grounds
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