Unravelling migration connectivity reveals unsustainable hunting of the declining ortolan bunting.

In France, illegal hunting of the endangered ortolan bunting Emberiza hortulana has been defended for the sake of tradition and gastronomy. Hunters argued that ortolan buntings trapped in southwest France originate from large and stable populations across the whole of Europe. Yet, the European Commission referred France to the Court of Justice of the European Union (EU) in December 2016 for infringements to legislation (IP/16/4213). To better assess the impact of hunting in France, we combined Pan-European data from archival light loggers, stable isotopes, and genetics to determine the migration strategy of the species across continents. Ortolan buntings migrating through France come from northern and western populations, which are small, fragmented and declining. Population viability modeling further revealed that harvesting in southwest France is far from sustainable and increases extinction risk. These results provide the sufficient scientific evidence for justifying the ban on ortolan harvesting in France.

Nonparametric spatial regression of survival probability: visualization of population sinks in Eurasian woodcock.

Both evolutionary ecologists and wildlife managers make inference based on how fitness and demography vary in space. Spatial variation in survival can be difficult to assess in the wild because (1) multisite study designs are not well suited to populations that are continuously distributed across a large area and (2) available statistical models accounting for detectability less than 1.0 do not easily cope with geographical coordinates. Here we use penalized splines within a Bayesian state-space modeling framework to estimate and visualize survival probability in two dimensions. The approach is flexible in that no parametric form for the relationship between survival and coordinates need be specified a priori. To illustrate our method, we study a game species, the Eurasian Woodcock Scolopax rusticola, based on band recovery data (5000 individuals) collected over a > 50 000-km2 area in west-central France with contrasted habitats and hunting pressures. We find that spatial variation in survival probability matches an index of hunting pressure and creates a mosaic of population sources and sinks. Such analyses could provide guidance concerning the spatial management of hunting intensity or could be used to identify pathways of spatial variation in fitness, for example, to study adaptation to changing landscape and climate.

Using stable hydrogen and oxygen isotope measurements of feathers to infer geographical origins of migrating European birds.

Successful application of stable-hydrogen isotope measurements (deltaDf) of feathers to track origins of migratory birds and other wildlife requires a fundamental understanding of the correlation between deltaDf and deuterium patterns in rainfall (deltaDp) over continental scales. A strong correlation between deltaDp and deltaDf has been confirmed for birds and insects in North America, but not yet for other continents. Here, we compare deltaDf data from resident European birds to new deltaDp basemaps for Europe. Three maps, representing growing-season and mean annual deltaDp estimates from an elevation-explicit, detrended interpolation model and growing-season deltaDp estimates from simple Kriging, all indicate that strong isotope gradients occur across Europe with a general depletion occurring in a northeast direction. The feather data, representing 141 individuals of 25 avian species from 38 sites, ranged from -131 to -38 per thousand. Regression analysis showed that strong correlations existed between both mean annual and growing-season deltaDp estimated by detrended interpolation and deltaDf of non-aquatic and non-corvid birds (r2=0.66 and 0.65, respectively). We also examined mean annual and growing-season delta18Op vs. delta18Of for our samples. Both oxygen regressions were similar (r2=0.56 and 0.57, respectively) but poorer than for deuterium. Our study reveals that deltaD measurements of feathers from migratory birds in Europe may be used to track their origin and movements, and so provide a powerful investigative tool for avian migration research in Europe.