Migration phenology determines niche use of East Asian buntings (Emberizidae) during stopover

Abstract

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. However, stopover sites are crucial for migratory birds. They are often used by a multitude of species, which could lead to increased competition. 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 flyway. We used bird ringing data to evaluate morphological similarity as well as niche overlap on the trophic, spatial, and temporal dimension. Bill morphology was used as a proxy for their trophic niche. We were able to prove that a majority of the species occupies well-defined stopover niches on at least one of the dimensions. Niche breadth and niche overlap differ between spring and autumn season with higher overlap found during spring. Morphological differences are mostly related to overall size and wing pointedness. The temporal dimension is most important for segregation among the studied species. Furthermore, all species seem to exhibit a rather strict and consistent phenological pattern. Their occurrence at the study site is highly correlated with their geographic origin and the length of their migration route. 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.

Weather conditions affect spring and autumn migration of Siberian leaf warblers

“…The studied species are likely mainly following their innate migration schedule. Consistent migration timing between years was also found for Emberiza buntings at our study site (Heim et al 2018b). This might especially be true for spring migration, when competition is high to arrive early at the breeding grounds (Nilsson et al 2013), which could force individuals to continue migration under sub-optimal weather conditions.…”

Factors controlling the migration phenology of Siberian Phylloscopus species

“…The study site is located 60 km southeast of the city of Blagoveshchensk (49°55′08,27″N, 127°40′19,93″E). Birds were trapped with mist-nets using a constant-effort-site approach in a variety of different habitat types (for details see Heim et al 2018). We included the following species: Yellow-browed Warbler Phylloscopus inornatus, Arctic Warbler P. borealis, Two-barred Warbler P. plumbeitarsus, Pale-legged Leaf Warbler P. tenellipes, Dusky Warbler P. fuscatus, Radde's Warbler P. schwarzi and Pallas's Leaf Warbler P. proregulus.…”

“…Despite the fact that the East Asian migratory flyway is the largest of all other flyways and holds the highest diversity of migratory songbirds, we have only very limited information about the migration ecology and phenology for most of the species (Yong et al 2015). Short-term but standardized bird-ringing activities have resulted in a better understanding of feeding habits, habitat use, and migration strategies in several groups of Asian passerines, for example small thrushes (Wang et al 2006;Maslovsky et al 2018), and buntings (Nam et al 2011;Heim et al 2018). However, in the last two decades the most studied group in Asia were the leaf warblers.…”

Endogenous Programs and Flexibility in Bird Migration

“…Ultimately, combined ecological and mechanistic studies may explain why some species strictly adhere to spatiotemporal programs whereas others are flexible, and how selection pressures, from competitive temporal niche segregation (Heim et al, 2018) to climate change, may shape migrations in the future. We hope that our overview will encourage future cross-over between approaches that focus on annualcycle programs and those that focus on the environment, as jointly these components enable migratory birds to carry out their great journeys.…”