Seabirds are among the most threatened groups of birds, and predation by invasive mammals is one of the most acute threats at their island breeding stations. Island restoration projects increasingly involve the eradication of invasive non-native mammals, with benefits for seabirds and other island fauna. To date, demonstrated benefits of invasive mammal eradication include increased seabird nesting success and enhanced adult survival. However, the recovery dynamics of seabird populations have not been documented. Drawing on data from across the world, we assemble population growth rates (k) of 181 seabird populations of 69 species following successful eradication projects. After successful eradication, the median growth rate was 1.119 and populations with positive growth (k > 1; n = 151) greatly outnumbered those in decline (k < 1; n = 23, and seven showed no population change). Population growth was faster (1) at newly established colonies compared to those already established, (2) in the first few years after eradication, (3) among gulls and terns compared to other seabird groups, and (4) when several invasive mammals were eradicated together in the course of the restoration project. The first two points suggest immigration is important for colony growth, the third point reflects the relative lack of philopatry among gulls and terns while the fourth reinforces current best practise, the removal of all invasive mammals where feasible.

When animals move across a landscape, they alternate between active searching phases in areas with high prey density and commuting phases towards and in-between profitable feeding patches. Such active searching movements are more sinuous than travelling movements, and supposedly more costly in energy. Here we provide an empirical validation of this long-lasting assumption. To this end, we evaluated simultaneously energy expenditure and trajectory in northern gannets (Morus bassanus) using GPS loggers, dive recorders and three-dimensional accelerometers. Three behavioural states were determined from GPS data: foraging, when birds actively searched for prey (high tortuosity, medium speed); travelling, when birds were commuting (straight trajectory, high speed); and resting (straight trajectory, low speed). Overall dynamic body acceleration, calculated from acceleration data, was used as a proxy for energy expenditure during flight. The impact of windscape characteristics (wind force and direction) upon flight costs was also tested. Energy expenditure of northern gannets was higher during sinuous foraging flight than during more rectilinear travelling flight, demonstrating that turns are indeed costly. Yet wind force and direction also strongly shaped flight energy expenditure; within any behavioural state it was less costly to fly with the wind than against it, and less costly to fly with strong winds. Despite the major flight costs of wind action, birds did not fully optimize their flight track relative to wind direction, probably because of prey distributions relative to the coastline and wind predictability. Our study illustrates how both tortuosity and windscape shape the foraging costs of marine predators such as northern gannets.KEY WORDS: Energetics, Accelerometry, State-space model, Foraging, Seabird, Wind INTRODUCTIONAnimal energetics play a central role in ecology by conditioning individual fitness, population processes and, ultimately, trophodynamics and ecosystem functioning (Brown et al., 1993). Energy balance is determined by energy expenditure and food acquisition, and optimal foraging theory predicts that animals should minimise the former while maximizing the latter (Bell, 1991). The study of energy expenditure in foraging animals is therefore

Grey (Halichoerus grypus) and harbour seals (Phoca vitulina) are sympatric seal species, but they display distinct strategies of habitat use and connectivity between haulout sites. The distribution patterns and variations in relative abundance of both species were investigated along the French coast of the English Channel, at the southern limit of their range where seal numbers are increasing. Regular censuses conducted at all main haulout sites in mainland France showed significant seasonal variations at most sites, with more harbour seals counted during summer (breeding and moulting seasons), and more grey seals during summer only in the eastern English Channel. Trends in maximum haulout numbers at haulout sites showed a significant increase over the last five years, ranging from 9.7 to 30.9% per year for harbour seals, and from 5.8% (in the western English Channel) to 49.2% (in the eastern English Channel) per year for grey seals. These rates of increase in grey seal numbers are not linked to local pup production and most probably result from seal movements from the southwest British Isles and the North Sea, respectively. Aerial surveys conducted across the English Channel showed that most seal observations at sea were concentrated in the northeastern English Channel. Telemetry showed that the 28 harbour seals tracked remained highly coastal, within a radius of 100km from their haulout sites, and did not move to other known colonies. Grey seals moved much greater distances, reaching up to 1200 km from their capture site. More than half of the 45 grey seals tracked crossed the English Channel, especially during the breeding season, moving to known colonies in the southwest British Isles and the North Sea. Combining individual tracks and long-term surveys of the seal populations allowed a better understanding of the dynamics of these populations and their connectivity at a larger regional scale. The findings provide direct information for the management of grey and harbour seals within the frame of the Marine Strategy Framework Directive, and highlight focus areas where potential interactions between the two species should be monitored.

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Phenology of biological systems is the expression of selective pressures forcing organisms to match their energy requirements to seasonal variations in resource availability. For longdistance migrant organisms, migration strategy is shaped by the availability and quality of stopovers during a precise time period. Ongoing climate changes alter the usual spatial and temporal distribution of resources, and, as a result, migrant species return earlier to their breeding grounds. Less is known on the evolution and determinants of timing of departure to wintering grounds, i.e. postbreeding migration. We analysed timing of post-nuptial migration and stopover strategy with capture-mark-recapture (CMR) data in 2 reedbed insectivorous passerines: the sedge warbler Acrocephalus schoenobaenus, specialised on a thermo-dependant prey, and the generalist reed warbler A. scirpaceus. Spring temperatures increased through years (0.16 ± 0.047°C yr ), whereas it was not related to autumnal temperatures. We suggest that this results from a major time shift (i.e. advance) in biomass production caused by global warming. Stopover duration (estimated by CMR analysis) was positively related to body mass gain, with a trend for a stronger effect in the specialised species. However, neither stopover duration nor body mass gain were related to spring temperature, suggesting that the advance in migration timing efficiently adapted bird phenology to temporal variations in resources.