Segregation can At such stopover sites, migrants often share space with other con- and be found on different dimensions (Pianka 1981): there can be tempo- heterospecific birds. bioecology and sociology (Popielarz and Neal 2007). cept itself dates back to Grinnel (1917) and is now widely applied in Consequently, many migratory birds do need to replenish energy stores during migration at intermittent stopover sites (Klaassen 1996). The niche con- Migratory flights are energetically costly (Wikelski et al. Introduction Those niches are shaped by competition with other species, resulting in segregation or resource partitioning (Pianka 1981). Key words: bird migration, Emberiza, habitat use, non-breeding, phenology, stopover. We assume that buntings are able to use available resources opportunistically during stopover, while trying to follow a precise schedule in order to avoid competition and to ensure individual fitness. Their occurrence at the study site is highly correlated with their geo- graphic origin and the length of their migration route. Furthermore, all species seem to exhibit a rather strict and con- sistent phenological pattern. The temporal dimension is most important for segre- gation among the studied species.
Morphological differences are mostly related to overall size and wing pointedness. Niche breadth and niche overlap differ between spring and autumn season with higher overlap found during spring. We were able to prove that a majority of the species occupies well-defined stopover niches on at least one of the dimensions. Bill morphology was used as a proxy for their trophic niche. We used bird ringing data to evaluate morphological similarity as well as niche overlap on the trophic, spatial, and temporal dimension. In this work, we investigated niche use of 8 migratory and closely related Emberiza bunting species at a stopover site in Far East Russia, situated on the poorly studied East Asian fly- way. They are often used by a multitude of species, which could lead to increased competition. However, stopover sites are crucial for migratory birds. Stopover niche utilization of birds during migration has not gained much attention so far, since the majority of the studies focuses on breeding or wintering areas. Heim, Wieland Eccard, Jana, A Bairlein, Franz Migration phenology determines niche use of East Asian buntings (Emberizidae) during stopover Migration phenology determines niche use of East Asian buntings (Emberizidae) during stopover
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