Isotopic assignment to origins of Eurasian Woodcock wintering in Britain and Ireland

Quantifying links between breeding, stopover and non‐breeding locations is critical to the management and conservation of migratory birds, particularly if they are hunted on migration and in winter. Endogenous markers such as stable isotopes provide a means of estimating natal or breeding origins and hence the degree of migratory connectivity between breeding and wintering areas. We used a stable hydrogen isotope ( δ 2 H) isoscape for Europe and 2 H analysis of feathers from harvested birds to estimate the natal and moulting origins of Eurasian Woodcock Scolopax rusticola wintering in Britain and Ireland. Using feathers collected from known locations across the breeding range, we established the relationship between the hydrogen isotope composition of feathers ( δ 2 H f ) and mean annual detrended precipitation ( δ 2 H p ) for Woodcock in Europe. We used a spatially explicit Bayesian assignment to estimate probable origins for each δ 2 H f value. Our results indicated broad‐front migration of Woodcock to Britain and Ireland, with most birds originating from Fennoscandia, the Baltic states, Belarus and western Russia. Migratory connectivity between breeding areas and wintering regions was low, but there was a difference in δ 2 H f values between six winter sampling regions, which was consistent with parallel migration routes from northern and eastern Europe. The estimated proportion of Woodcock shot that were residents averaged 10.3 ± 3.3% across winter regions, and British birds were present in winter in regions where they do not currently breed.