Stable isotopes (δD) delineate the origins and migratory connectivity of harvested animals: the case of European woodpigeons

Quantifying connectivity between breeding, stopover, and wintering locations is critical to the management and conservation of migratory animals. Mark-recapture approaches to establishing connectivity are limited due to marking location bias and poor recovery. Alternatively, endogenous markers like stable isotopes can augment extrinsic markers and help to overcome their limitations. We used a stable hydrogen isotope (delta D) isoscape for Europe and delta D analysis of feathers from harvested woodpigeons Columba palumbus in France, the Iberian Peninsula, and Corsica to estimate their natal origins. We propagated error associated with the relationship between deuterium in feathers (delta D-f) and mean growing-season precipitation (delta D-p) for woodpigeons in Europe. For every delta D-f value, we estimated a range of possible delta D-p values and used this to map the probability of origin. We estimated that similar to 50% of the woodpigeon harvest in France was comprised of residents or from nearby countries to the east. About 30% of the take were medium-distance migrants, and about 10% were long-distance migrants from Scandinavia, northwest Russia and the Baltic. A greater proportion of the long-distance migrants were taken in Spain. In Corsica, birds primarily originated from northern Italy to the Ukraine. The proportion of northern migrants harvested decreased with latitude, suggesting a leapfrog migration pattern. Birds harvested at lower latitudes showed an inverse relationship between wing length and delta D-f, which suggested that longer-distance migrants had longer wings. Synthesis and applications. This is the first application of stable isotope methodology to quantify population structure and migratory connectivity for a European game species. In addition, we used statistical approaches accounting for potential geospatial assignment errors. Most of the French woodpigeons harvested are resident birds, which suggests that local management of the hunt in France may be most effective. However, southwestern France appeared to take a somewhat greater proportion of migrant woodpigeons, and thus, conservation and management of woodpigeons in France should recognize regional differences. Our approach provided a methodological template that can be applied to questions of migratory connectivity for numerous species of game and non-game migrant birds.