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.
Plasma levels of corticosterone often mirror changes in body condition and parental effort. In seabirds, the brooding of young chicks is often paralleled by a marked decline in adult body condition. This may reflect the trade-off between the needs of the chick to be fed regularly and brooded, and that of the adult to spend enough time at sea to restore its body reserves and find food for the chick. In this paper, we describe changes in body condition and baseline corticosterone levels in a tropical seabird, the Red-footed Booby Sula sula , in which the chick is continuously brooded for 5-6 weeks. Body condition did not decline during the brooding period. Female body condition remained stable throughout breeding whereas male body condition declined significantly during the late chick-rearing period. Baseline corticosterone levels were low during the prelaying phase, increased significantly during incubation and were highest during the brooding period. Later in the chick-rearing period, baseline corticosterone levels decreased markedly in females, but stayed elevated in males. There was no correlation between baseline corticosterone and body condition. Because of the chick's slow growth and reduced daily need for food, brooding in Red-footed Boobies may not require a marked increase in parental effort, and the rise in corticosterone levels is probably more a reflection of slight changes in foraging activity. Red-footed Booby males are 15% smaller than females and we suggest that the decline in male body condition during the late chick-rearing period is likely to result from higher energetic flight costs or a lower foraging efficiency imposed by a smaller body size.
Summary 1.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. 2. We used a stable hydrogen isotope ( δ D) isoscape for Europe and δ D analysis of feathers from harvested woodpigeons Columba palumbus in France, the Iberian Peninsula, and Corsica to estimate their natal origins. 3. We propagated error associated with the relationship between deuterium in feathers ( δ D f ) and mean growing-season precipitation ( δ D p ) for woodpigeons in Europe. For every δ D f value, we estimated a range of possible δ D p values and used this to map the probability of origin. 4. We estimated that ~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. 5. 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 δ D f , which suggested that longer-distance migrants had longer wings. 6. 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.
The identification of migration routes, wintering grounds and stopover sites are crucial issues for the understanding of the Palearctic-African bird migration system as well as for the development of relevant conservation strategies for trans-Saharan migrants. Using miniaturized light-level geolocators we report a comprehensive and detailed year round track of a granivorous trans-Saharan migrant, the European Turtle Dove (Streptopelia turtur). From five recovered loggers, our data provide new insights on migratory journeys and winter destinations of Turtle Doves originating from a breeding population in Western France. Data confirm that Turtle Doves wintered in West Africa. The main wintering area encompassed Western Mali, the Inner Delta Niger and the Malian/Mauritanian border. Some individuals also extended their wintering ranges over North Guinea, North-West of Burkina Faso and the Ivory-Coast. Our results reveal that all individuals did not spend the winter period at a single location; some of them experienced a clear eastward shift of several hundred kilometres. We also found evidence for a loop migration pattern, with a post-breeding migration flyway lying west of the spring route. Finally, we found that on their way back to breeding grounds Turtle Doves needed to refuel after crossing the Sahara desert. Contrary to previous suggestions, our data reveal that birds used stopover sites for several weeks, presumably in Morocco and North Algeria. This later finding is a crucial issue for future conservation strategies because environmental conditions on these staging areas might play a pivotal role in population dynamics of this declining species.
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