Recent changes in the seasonal timing (phenology) of familiar biological events have been one of the most conspicuous signs of climate change. However, the lack of a standardized approach to analysing change has hampered assessment of consistency in such changes among different taxa and trophic levels and across freshwater, terrestrial and marine environments. We present a standardized assessment of 25 532 rates of phenological change for 726 UK terrestrial, freshwater and marine taxa. The majority of spring and summer events have advanced, and more rapidly than previously documented. Such consistency is indicative of shared large scale drivers. Furthermore, average rates of change have accelerated in a way that is consistent with observed warming trends. Less coherent patterns in some groups of organisms point to the agency of more local scale processes and multiple drivers. For the first time we show a broad scale signal of differential phenological change among trophic levels; across environments advances in timing were slowest for secondary consumers, thus heightening the potential risk of temporal mismatch in key trophic interactions. If current patterns and rates of phenological change are indicative of future trends, future climate warming may exacerbate trophic mismatching, further disrupting the functioning, persistence and resilience of many ecosystems and having a major impact on ecosystem services.

Summary: Abundant mid‐trophic pelagic fish often play a central role in marine ecosystems, both as links between zooplankton and top predators and as important fishery targets. In the North Sea, the lesser sandeel occupies this position, being the main prey of many bird, mammal and fish predators and the target of a major industrial fishery. However, since 2003, sandeel landings have decreased by > 50%, and many sandeel‐dependent seabirds experienced breeding failures in 2004. Despite the major economic implications, current understanding of the regulation of key constituents of this ecosystem is poor. Sandeel abundance may be regulated ‘bottom‐up’ by food abundance, often thought to be under climatic control, or ‘top‐down’ by natural or fishery predation. We tested predictions from these two hypotheses by combining unique long‐term data sets (1973–2003) on seabird breeding productivity from the Isle of May, SE Scotland, and plankton and fish larvae from the Continuous Plankton Recorder survey. We also tested whether seabird breeding productivity was more tightly linked to sandeel biomass or quality (size) of individual fish. The biomass of larval sandeels increased two‐ to threefold over the study period and was positively associated with proxies of the abundance of their plankton prey. Breeding productivity of four seabirds bringing multiple prey items to their offspring was positively related to sandeel larval biomass with a 1‐year lag, indicating dependence on 1‐year‐old fish, but in one species bringing individual fish it was strongly associated with the size of adult sandeels. These links are consistent with bottom‐up ecosystem regulation and, with evidence from previous studies, indicate how climate‐driven changes in plankton communities can affect top predators and potentially human fisheries through the dynamics of key mid‐trophic fish. However, the failing recruitment to adult sandeel stocks and the exceptionally low seabird breeding productivity in 2004 were not associated with low sandeel larval biomass in 2003, so other mechanisms (e.g. predation, lack of suitable food after metamorphosis) must have been important in this case. Understanding ecosystem regulation is extremely important for predicting the fate of keystone species, such as sandeels, and their predators.

Evolutionary theories of senescence predict that rates of decline in performance parameters should be shaped by early-life trade-offs between reproduction and somatic maintenance. Here we investigate factors influencing the rate of reproductive senescence in a long-lived seabird, the common guillemot Uria aalge, using data collected over a 23-year period. In the last 3 years of life, individual guillemots had significantly reduced breeding success and were less likely to hold a site or attempt to breed. Females senesced at a significantly faster rate than males. At the individual level, high levels of reproductive output earlier in life were associated with increased senescence later in life. This trade-off between early- and late-life reproduction was evident independent of the fact that as birds age, they breed later in the season. The rate of senescence was additionally dependent on environmental conditions experienced earlier in life, with evidence that harsh conditions amplified later declines in breeding success. Overall, individuals with intermediate levels of early-life productivity lived longer. These results provide support for the antagonistic-pleiotropy and disposable-soma theories of senescence and demonstrate for the first time in a wild bird population that increased rates of senescence in reproductive performance are associated with varying costs of reproduction early in life.

Aim  An understanding of the non‐breeding distribution and ecology of migratory species is necessary for successful conservation. Many seabirds spend the non‐breeding season far from land, and information on their distribution during this time is very limited. The black‐legged kittiwake, Rissa tridactyla, is a widespread and numerous seabird in the North Atlantic and Pacific, but breeding populations throughout the Atlantic range have declined recently. To help understand the reasons for the declines, we tracked adults from colonies throughout the Atlantic range over the non‐breeding season using light‐based geolocation.Location  North Atlantic.Methods  Geolocation data loggers were deployed on breeding kittiwakes from 19 colonies in 2008 and 2009 and retrieved in 2009 and 2010. Data from 236 loggers were processed and plotted using GIS. Size and composition of wintering populations were estimated using information on breeding population size.Results  Most tracked birds spent the winter in the West Atlantic, between Newfoundland and the Mid‐Atlantic Ridge, including in offshore, deep‐water areas. Some birds (mainly local breeders) wintered in the North Sea and west of the British Isles. There was a large overlap in winter distributions of birds from different colonies, and colonies closer to each other showed larger overlap. We estimated that 80% of the 4.5 million adult kittiwakes in the Atlantic wintered west of the Mid‐Atlantic Ridge, with only birds from Ireland and western Britain staying mainly on the European side.Main conclusions  The high degree of mixing in winter of kittiwakes breeding in various parts of the Atlantic range implies that the overall population could be sensitive to potentially deteriorating environmental conditions in the West Atlantic, e.g. owing to lack of food or pollution. Our approach to estimating the size and composition of wintering populations should contribute to improved management of birds faced with such challenges.