Moult of Guinea savanna passerines in West Africa

Mcgregor, Ross; Ottosson, Ulf; Cresswell, Will

doi:10.2989/ostrich.2007.78.2.26.106

Cited by 7 publications

(1 citation statement)

References 16 publications

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“…For example, at some of our sampling sites δD in precipitation varies between +20‰ in November to −30‰ in July (Bowen et al 2005; <http://wateriso.eas.purdue.edu/waterisotopes/pages/data_access/da_main.html>, accessed 27 March 2010). Given that the timing of moult is poorly known and potentially poorly constrained for some resident species (Aidley and Wilkinson 1987, McGregor et al 2007), isotope gradients derived from multiple species that may moult at different times of the year may not be very meaningful (Farmer et al 2008, Kelly et al 2008).…”

Section: Discussionmentioning

confidence: 99%

High variation reduces the value of feather stable isotope ratios in identifying new wintering areas for aquatic warblers Acrocephalus paludicola in West Africa

Oppel¹,

Pain²,

Lindsell³

et al. 2011

Journal of Avian Biology

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Stable isotope analysis of feathers can be useful in the study of seasonal interactions and migratory connectivity in birds. For the PalaearcticÁAfrican migration system, however, the lack of isotope data from feathers of known origin in Africa renders the geographic assignment of birds captured on European breeding grounds to potential wintering areas problematic. Rectrices of the threatened aquatic warbler Acrocephalus paludicola grown in Africa were sampled across six European countries to assess whether birds in different breeding populations shared similar isotopic signatures and so were likely to have wintered in the same region in Africa. Freshly grown feathers of aquatic warblers collected at the only known wintering site in Senegal showed high variation in carbon, nitrogen, and hydrogen isotope ratios. Due to similarly high variation in isotope ratios of African-grown feathers within all breeding populations, it was not possible to determine whether different populations wintered in different regions. However, isotope signatures of 20% of birds captured on European breeding grounds fell outside the range of those captured in Senegal, suggesting a wider wintering distribution than is currently known. We therefore assessed whether the origin of these feathers could be estimated by trying to establish isotopic gradients across sub-Saharan West Africa. Feathers of three ecologically similar surrogate species were sampled from wetlands across a 3000 km east-west and a 2000 km northÁsouth transect. Within-site variation in feather isotope ratios was frequently larger than the difference predicted by gradients across West Africa. Thus, predicting the origin of individual feathers using single-isotope gradients was not reliable. The large within-site variability of feather isotope ratios of a habitat specialist species like the aquatic warbler indicates that using feather isotope ratios will require large sample sizes from many locations, and may thus not be an efficient tool in identifying wintering areas of PalaearcticÁ African migrants.Carry-over effects between seasons and the potential for non-breeding mortality to act as a limiting factor for bird populations render the identification of non-breeding areas very important for the conservation of migratory birds (Webster et al.

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