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We investigated the feeding ecology and foraging location of migrating and nursing northern fur seal (Callorhinus ursinus) adult females and migrating juvenile males from the Pribilof Islands, Alaska, using carbon (δ13C) and nitrogen (δ15N) isotope analysis of fur seal skin and whole potential prey. Post-parturient and lactating females had mean δ15N values significantly (0.8‰) higher than pregnant,...
The remains of northern fur seals (Callorhinus ursinus) are among the most abundant of pinniped elements recovered from mainland coastal archaeological sites in both California and Oregon. This is surprising as all contemporary northern fur seals breed exclusively on offshore islands, primarily at high latitudes, and the species is otherwise pelagic. The vulnerability of these animals to human predation...
We studied the patterns and rates of migration among habitat patches for five species of checkerspot butterflies (Lepidoptera: Melitaeini) in Finland: Euphydryas aurinia, E. maturna, Melitaea cinxia, M. diamina and M. athalia. We applied the virtual migration (VM) model to mark-release-recapture data collected from multiple populations. The model includes parameters describing migration and survival...
Despite the importance of dispersal to ecology, accurate estimates of dispersal rates are often difficult to obtain, especially for organisms that rely on passive dispersal of propagules to colonize new sites. To investigate potential dispersal vectors and relative colonization rates of zooplankton, we conducted a field experiment in which we restricted potential dispersal vectors (insects, birds,...
Long-distance passerine migrants deposit substantial fat stores to fuel their migratory journey. Many of those migratory birds arrive at their northerly breeding grounds with larger fat stores than were necessary to reach their breeding area. Both male and female American Redstarts (Setophaga ruticilla) arrived to breed in Michigans Upper Peninsula with fat, and females arrived with more fat than...
Hydrogen stable isotope analysis of feathers is an important tool for estimating the natal or breeding latitudes of nearctic-neotropical migratory birds. This method is based on the latitudinal variation of hydrogen stable isotope ratios in precipitation in North America (Dp) and the inheritance of this variation in newly formed feathers (Df). We hypothesized that the typically strong relationship...
In thermally stratified lakes with a deep chlorophyll maximum (DCM), Daphnia face a trade-off between food availability and optimum development temperatures. We hypothesize that Daphnia optimize their fitness by allocating the time spent in the different vertical habitats depending on the distribution of algal resources and the temperature gradient. We used the plankton towers (large indoor mesocosms)...
Weather and climatic conditions may impact on the phenology and morphology of birds, and thereby affect their survival rate and population dynamics. We examined the North Atlantic Oscillation (NAO), precipitation in the Sahel zone, temperatures in the wintering grounds, on the migration route, and in the breeding area in relation to arrival dates and six morphological measures (wing, tarsus, bill,...
Successful application of stable-hydrogen isotope measurements (δDf) of feathers to track origins of migratory birds and other wildlife requires a fundamental understanding of the correlation between δDf and deuterium patterns in rainfall (δDp) over continental scales. A strong correlation between δDp and δDf has been confirmed for birds and insects in North America, but not yet for other continents...
Stable isotopes are being increasingly used in wildlife forensics as means of determining the origin and movement of animals. The heavy isotope content of precipitated water and snow (δDp, δ18Op) varies widely and systematically across the globe, providing a label that is incorporated through diet into animal tissue. As a result, these isotopes are potentially ideal tracers of geographic origin. The...
We used feathers of known origin collected from across the breeding range of a migratory shorebird to test the use of isotope tracers for assigning breeding origins. We analyzed δD, δ13C, and δ15N in feathers from 75 mountain plover (Charadrius montanus) chicks sampled in 2001 and from 119 chicks sampled in 2002. We estimated parameters for continuous-response inverse regression models and for discrete-response...
Like other pond-breeding amphibians, the natterjack toad (Bufo calamita) typically presents a patchy distribution. Because the species experiences high probabilities of local population extinction, its persistence within landscapes relies on both local and landscape-scale processes [dispersal allowing the (re)colonization of habitat patches]. However, the structure and composition of the matrix surrounding...
The phenology of avian migration appears to be changing in response to climate change. Seemingly contradictory differences in the timing of these annual cycles have been reported in published studies. We show that differences between studies in the choice of songbird species, as well as in the measurements of migration phenology, can explain most of the reported differences. Furthermore, while earlier...
Teeth from male sperm whales (Physeter macrocephalus) stranded in the North-eastern Atlantic were used to determine whether chronological profiles of stable isotope ratios of C (δ13C) and N (δ15N) across dentine growth layers could be used to detect known ontogenetic benchmarks in movements and trophic ecology. Profiles showed a general decrease in δ13C (median = 1.91‰) and an increase in δ15N (median = 2...
Continent-wide variation in hydrogen isotopic composition of precipitation is incorporated into animal diets, providing an intrinsic marker of geographic location at the time of tissue growth. Feathers from migratory birds are now frequently analyzed for stable-hydrogen isotopes (δD) to estimate the location of individuals during a preceding molt. Using known-origin birds, we tested several assumptions...
Dispersal is a key process in metapopulations, as migrants genetically connect populations and enable the colonization of empty habitat patches. Sub-populations may differ in their numerical contribution of migrants within a metapopulation. This has strong implications on evolutionary and ecological dynamics and has led to two different hypotheses about the Daphnia metapopulation studied here: the...
Deuterium isotope analyses have revolutionized the study of migratory connectivity because global gradients of deuterium in precipitation (δDP) are expressed on a continental scale. Several authors have constructed continental scale base maps of δDP to provide a spatial reference for studying the movement patterns of migratory species and, although they are very useful, these maps present a static,...
Demographic rates of migratory species passing through several areas during their annual cycle may be affected by environmental conditions at each of these areas. Recent studies provide evidence that their impact is not necessarily immediate, but can be delayed. We studied survival, reproductive success and arrival date at the breeding grounds of red-backed shrikes Lanius collurio, a trans-Saharan...
Salt stress can suppress the immune function of fish and other aquatic animals, but such an effect has not yet been examined in air-breathing vertebrates that frequently cope with waters (and prey) of contrasting salinities. We investigated the effects of seawater salinity on the strength and cost of mounting an immune response in the dunlin Calidris alpina, a long-distance migratory shorebird that...
Stable isotopes can illuminate resource usage by organisms, but effective interpretation is predicated on laboratory validation. Here we develop stable isotope clocks to track resource shifts in anadromous rainbow trout (Oncorhynchus mykiss). We used a diet-switch experiment and model fitting to quantify N stable isotope (δ15N) turnover rates and discrimination factors for seven tissues: plasma, liver,...
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