Potential climatic changes of the near future have important characteristics that differentiate them from the largest magnitude and most rapid of climatic changes of the Quaternary. These potential climatic changes are thus a cause for considerable concern in terms of their possible impacts upon biodiversity. Birds, in common with other terrestrial organisms, are expected to exhibit one of two general responses to climatic change: they may adapt to the changed conditions without shifting location, or they may show a spatial response, adjusting their geographical distribution in response to the changing climate. The Quaternary geological record provides examples of organisms that responded to the climatic fluctuations of that period in each of these ways, but also indicates that the two are not alternative responses but components of the same overall predominantly spatial response. Species unable to achieve a sufficient response by either or both of these mechanisms will be at risk of extinction; the Quaternary record documents examples of such extinctions. Relationships between the geographical distributions of birds and present climate have been modelled for species breeding in both Europe and Africa. The resulting models have very high goodness‐of‐fit and provide a basis for assessing the potential impacts of anthropogenic climatic changes upon avian species richness in the two continents. Simulations made for a range of general circulation model projections of late 21st century climate lead to the conclusion that the impacts upon birds are likely to be substantial. The boundaries of many species’ potential geographical distributions are likely to be shifted  1000 km. There is likely to be a general decline in avian species richness, with the mean extent of species’ potential geographical distributions likely to decrease. Species with restricted distributions and specialized species of particular biomes are likely to suffer the greatest impacts. Migrant species are likely to suffer especially large impacts as climatic change alters both their breeding and wintering areas, as well as critical stopover sites, and also potentially increases the distances they must migrate seasonally. Without implementation of new conservation measures, these impacts will be severe and are likely to be exacerbated by land‐use change and associated habitat fragmentation. Unless strenuous efforts are made to address the root causes of anthropogenic climatic change, much current effort to conserve biodiversity will be in vain.

The house mouse, Mus musculus , is one of the most widespread and well-studied invasive mammals on islands. It was thought to pose little risk to seabirds, but video evidence from Gough Island, South Atlantic Ocean shows house mice killing chicks of two IUCN-listed seabird species. Mouse-induced mortality in 2004 was a significant cause of extremely poor breeding success for Tristan albatrosses, Diomedea dabbenena (0.27 fledglings/pair), and Atlantic petrels, Pterodroma incerta (0.33). Population models show that these levels of predation are sufficient to cause population decreases. Unlike many other islands, mice are the only introduced mammals on Gough Island. However, restoration programmes to eradicate rats and other introduced mammals from islands are increasing the number of islands where mice are the sole alien mammals. If these mouse populations are released from the ecological effects of predators and competitors, they too may become predatory on seabird chicks.

Summary1. The potential of using stable isotope signatures of avian claws in order to infer diet and habitat use was investigated. 2. Highly significant relationships observed between stable carbon and nitrogen isotope ratios ( δ 13 C, δ 15 N) in the claws and body feathers of resident birds were expected since it was predicted that they were synthesized in the same habitat and approximately the same time of year. 3. Likewise the non-significant relationships observed between δ 13 C and δ 15 N in the claws and tertial feathers of neotropical migrant birds were also predicted since the claws were synthesized in the wintering area and the tertials in the breeding area. 4. The growth rates measured in the claws of five species of palearctic passerines provide evidence that this tissue should integrate dietary and habitat information over a medium temporal scale (probably weeks to months). 5. It is suggested that claws may offer a unique combination of attributes to the isotope ecologist: they are non-invasively sampled; metabolically inert but grow continuously, and are therefore a more flexible tool than feathers. 6. It is also suggested that that the stable isotope signatures in the claws of mammals and reptiles may provide similar information.

Although predicted some time ago, there has been little success in demonstrating that the overall f itness of migratory birds depends on the combined influences of their experiences over all seasons. We used stable carbon isotope signatures (␦ 13 C) in the claws of migrating black-throated blue warblers Dendroica caerulescens to infer their wintering habitats and investigated whether winter habitat selection can be linked to condition during migration. Resident bird species with low ␦ 13 C corresponded to selection of more mesic habitats, and migrating birds with low ␦ 13 C were in better condition than conspecif ics with higher ␦ 13 C signatures. These f indings concur with empirical observations on the wintering grounds, where dominants (mostly males) tend to exclude subordinates from mesic areas (considered to be high-quality habitats). We believe that variation in condition during migration may be one of the key factors determining differences in arrival times and condition at the breeding areas, which in turn have a major influence on reproductive success.

The rockhopper penguin (Eudyptes chrysocome) is a conspicuous apex marine predator that has experienced marked population declines throughout most of its circumpolar breeding distribution. The cause(s) for the declines remain elusive, but the relatively large spatio-temporal scale over which population decreases have occurred implies that ecosystem-scale, at-sea factors are likely to be involved. We employ stable isotope analyses of carbon ( 13 C/ 12 C, expressed as d 13 C) and nitrogen ( 15 N/ 14 N, d 15 N) in timeseries of rockhopper penguin feather samples, dating back to 1861, in order to reconstruct the species' ecological history. Specifically, we examine whether rockhopper penguin population decline has been associated with a shift towards lower primary productivity in the ecosystem in which they feed, or with a shift to a diet of lower trophic status and lower quality, and we use long-term temperature records to evaluate whether shifts in isotope ratios are associated with annual variations in sea surface temperature. Having controlled temporally for the Suess Effect and for increases in CO 2 concentrations in seawater, we found that overall, d 13 C signatures decreased significantly over time in rockhopper penguins from seven breeding sites, supporting the hypothesis that decreases in primary productivity, and hence, carrying capacity, for which d 13 C signature is a proxy, have been associated with the decline of penguin populations. There was some evidence of a long-term decline in d 15 N at some sites, and strong evidence that d 15 N signatures were negatively related to sea surface temperatures across sites, indicative of a shift in diet to prey of lower trophic status over time and in warm years. However, a siteby-site analysis revealed divergent isotopic trends among sites: five of seven sites exhibited significant temporal or temperature-related trends in isotope signatures. This study highlights the utility of stable isotope analyses when applied over relatively long timescales to apex predators.