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- Campos, Ana R., et al.
(författare)
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How do Robins Erithacus rubecula resident in Iberia respond to seasonal flooding by conspecific migrants?
- 2011
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Ingår i: Bird Study. - : Informa UK Limited. - 0006-3657 .- 1944-6705. ; 58:4, s. 435-442
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Tidskriftsartikel (refereegranskat)abstract
- Capsule The majority of Robins in Iberia are sedentary and stay in their nesting areas despite the pre- sumed increased competition that results from the seasonal flooding of the area by conspecific migrants. Aims To evaluate if Robins in Iberia are displaced from their nesting areas by the presence of large num- bers of competitors originating from higher latitudes. Methods Data from constant effort ringing sites were used to estimate the proportion of Robins that are strictly sedentary and the seasonal variation in Robin numbers. Hydrogen stable isotope ratios (d2H) in feathers, and sex ratios determined through molecular techniques, allowed an insight into the numerical importance of invading Robins from higher latitudes. Results Robins were more numerous outside the breeding season, with clear influxes in autumn. Around half of the locally nesting Robins were captured during winter, indicating they are truly sedentary. d2H in feathers suggests that a wide mixture of Robins from all European latitudes were present in winter, and these data, together with sex ratios, suggest that there may be similar numbers of local and foreign individ- uals in winter at the main study site. Conclusion Despite the occupation of their range by migrants, local birds are largely sedentary.
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| 2. |
- Catry, Paulo, et al.
(författare)
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Provenance does matter : links between winter trophic segregation and the migratory origins of European robins
- 2016
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 182:4, s. 985-994
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Tidskriftsartikel (refereegranskat)abstract
- Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ2H) in robin Erithacus rubecula feathers across Europe. We then use δ2H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ2H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ2H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds.
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