At the close of the Fourth International Polar Year, we take stock of the ecological consequences of recent climate change in the Arctic, focusing on effects at population, community, and ecosystem scales. Despite the buffering effect of landscape heterogeneity, Arctic ecosystems and the trophic relationships that structure them have been severely perturbed. These rapid changes may be a bellwether of changes to come at lower latitudes and have the potential to affect ecosystem services related to natural resources, food production, climate regulation, and cultural integrity. We highlight areas of ecological research that deserve priority as the Arctic continues to warm.

We relate variation in the timing of arrival by migrating birds breeding at northerly latitudes to individual differences in the prior accumulation of energy stores. Balancing starvation risks early in the season against the almost universal declining trend in reproductive prospects with advancing date is seen as an individual decision with fitness consequences. We review three studies implicating events at the staging sites or in winter in setting the individual migratory schedule. Climate change influences the timetable of a pied flycatcher (Ficedula hypoleuca) population breeding in The Netherlands and wintering in West Africa, followed since 1960. Mean air temperature in the period mid April‐mid May (arrival and laying) increased and laying date advanced by 10 days. Still, in recent years most birds did not lay early enough to maximise fitness (determined by recruitment and parental survival) whereas many parents achieved this goal in 1980–1985. As the flycatchers have not started to arrive earlier, some ecological constraint further upstream is postulated (possibly the hurdle of the crossing of Sahara and Mediterranean). The ability to follow individual migrants provides a second avenue to assess the fitness implications of migratory schedules. Thus, brightly coloured male bar‐tailed godwits (Limosa lapponica) captured in the Dutch Wadden Sea (the intermediate staging site linking a West African wintering area with breeding sites in arctic Russia) and traced with miniature radio‐transmitters did not depart early. The ‘best’ males (with bright breeding plumage) were picked up by the listening stations in Sweden 650 km further along the migratory route ten days later than the paler individuals. If early arrival confers the competitive advantage of prior occupancy but increases mortality, the ‘best’ males may be able to afford arriving later and thus avoid some of the survival costs. Return rate of the ‘bright’ males to the staging site in later seasons was indeed higher than for the ‘pale’, early males. Intensive observation of pink‐footed geese (Anser brachyrhynchus) fitted with coded neck‐collars substantiate the tight relationship between energy stores (fat) accumulated up to final departure from the final staging site (Vesterålen, N. Norway) en route to the nesting grounds (Spitsbergen) and subsequent success. The breeding outcome of individual parents (accompanied by juveniles or not) could be related to observations of body condition before departure (visual ‘abdominal profile index’). Recently, perceived conflicts with agriculture have resulted in widespread harassment by humans. The geese have: drastically shortened their stay on the Vesterålen, fail to achieve the body condition usual a decade ago and reproductive output has fallen. Although the geese are currently pioneering new staging sites, an adequate alternative has not materialised, underlining the critical role of the final take‐off site.

Intensification of agriculture since the 1950s has enhanced the availability, competitive ability, crude protein content, digestibility and extended growing seasons of forage grasses. Spilled cereal grain also provides a rich food source in autumn and in winter. Long-distance migratory herbivorous geese have rapidly exploited these feeding opportunities and most species have shown expansions in range and population size in the last 50 years. Results of long-term studies are presented from two Arctic-breeding populations, the Svalbard pink-footed goose and the Greenland white-fronted goose (GWFG). GWFGs have shown major habitat shifts since the 1950s from winter use of plant storage organs in natural wetlands to feeding on intensively managed farmland. Declines in local density on, and abandonment of, unmodified traditional wintering habitat and increased reproductive success among those birds wintering on farmland suggest that density-dependent processes were not the cause of the shift in this wintersite-faithful population. Based on enhanced nutrient and energy intake rates, we argue that observed shifts in both species from traditionally used natural habitats to intensively managed farmland on spring staging and wintering areas have not necessarily been the result of habitat destruction. Increased food intake rates and potential demographic benefits resulting from shifts to highly profitable foraging opportunities on increasingly intensively managed farmland, more likely explain increases in goose numbers in these populations. The geographically exploratory behaviour of subdominant individuals enables the discovery and exploitation of new winter feeding opportunities and hence range expansion. Recent destruction of traditional habitats and declines in farming at northern latitudes present fresh challenges to the well being of both populations. More urgently, Canada geese colonizing breeding and moulting habitats of white-fronted geese in Greenland are further affecting their reproductive output.

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Because of its applied character, wildlife science needs opportunities to summarise existing knowledge by reviewing, either by presenting leading ideas and results of study teams, or summarising adva nced knowledge of selec ted scientific or management problems. Reviews should be concise.

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Current estimates of goose population sizes in western Europe, a gap analysis and an assessment of trendsAktuella skattningar av gåsbeståndens storlek i västra Europa, analys av kunskapsluckor och utvärdering av trender

Summary 0[ In most situations that have been studied\ the creation of refuge areas for migratory waterfowl has generally increased the number of waterfowl using a site[ However\ experimental evidence to show that the increases were caused by reduced disturbance and not by confounding factors\ e[g[ improvement of habitat quality of the sites or general population increases\ is generally lacking[ 1[ In two Danish coastal wetlands\ waterfowl hunting was the most critical source of disturbance to autumn!staging waterfowl "Madsen 0887#[ To test whether hunting disturbance displaced birds from sites\ experimental refuge areas were established\ with hunting!free areas manipulated annually during a 3!year period\ followed by permanent refuge establishments\ monitored for a further 3 years[ 2[ In both areas\ experiments showed that quarry geese and dabbling ducks redis! tributed according to the position of the hunting!free areas\ whereas protected species did not[ In quarry geese\ there was a 5Ð7!fold increase in numbers from before to after the experiments^in quarry dabbling ducks there was a 3Ð49!fold increase[ Dabbling ducks extended the staging period into the winter[ Protected waterfowl as well as goldeneye and coot "both quarry species# did not redistribute^their numbers either~uctuated or increased "1 to × 49 fold#[ 3[ In quarry geese and dabbling ducks\ changes in food supplies "of the herbivorous species#\ intensities of recreational activities outside the refuge areas\ weather or overall population sizes could not explain the increases[ In protected species\ as well as goldeneye and coot\ trends in local numbers were in accordance with overall population trends for some species^in others\ the rate of increase in local numbers was higher than in overall population size[ 4[ In both areas\ species richness increased from before to after the experiments[ This was most pronounced in one of the areas where the refuge included shallow!watered areas in association with salt marshes[ 5[ It is concluded that prior to experiments\ waterfowl hunting caused a displacement of quarry species\ resulting in a species!poor waterfowl community[ Refuge creation is an e.cient management tool to improve the conservation value and biodiversity of wetlands of importance to waterfowl[ Key!words] shooting\ species diversity\ waterbirds[ Journal of Applied Ecology "0887# 24\ 287Ð306