Ecological theory predicts that animals with similar foraging strategies should not be able to co‐exist without segregating either in space, time or diet. In communities, intra‐specific competition is thought to be more intense than the competition among species, because of the lack of niche partitioning between conspecifics. Hence, while different seabird species can overlap in their foraging distribution, intra‐specific competition can drive the neighboring populations of the same species to spatial segregation of foraging areas. To investigate ecological segregation within and among species of diving seabirds, we used a multi‐species GPS‐tracking approach of seabirds of four species on a small island in the Southwest Atlantic. The present study goes beyond previous work by analyzing simultaneous effects of species and colonies. We observed strikingly strong spatial foraging segregation among birds of the same species, breeding in colonies as close as 2 km from each other. Conspecifics from neighboring colonies used foraging places adjacent to their own colony, and there was little or no overlap with birds from the other colony. A zone with increased predator concentration was completely avoided during foraging trips, likely contributing to the spatial segregation. In addition to spatial segregation, we also observed intra‐specific differences in other components of foraging behavior, such as time of day, dive depth and diet. These were most likely caused by optimal foraging of individuals in relation to habitat differences on a local scale, leading to a complex pattern of interactions with environmental covariates, in particular foraging daytime, foraging water layer temperature and depth, distance to coast and bathymetric depth of foraging areas. As mechanisms leading to the spatial segregation we propose a combination of optimal foraging and avoidance of predation.

The rockhopper penguins Eudyptes chrysocome have recently been split into the northern E. moseleyi and the southern E. chrysocome rockhopper penguin. It is therefore crucial to have a comprehensive understanding of the biology of each species in order to develop appropriate conservation measures. We investigated the breeding biology of the southern rockhopper on New Island, in the western part of the Falklands Islands, by following the breeding attempt of 160 pairs during the 2006/2007 season and examining the eVect of lay time and colony habitat on breeding success. SpeciWcally, we compared survival and growth parameters between A-and B-eggs and chicks from non-manipulated and artiWcially manipulated nests to investigate why southern rockhopper penguins in the Falkland Islands are more able to Xedge an A-egg (Wrst laid) than conspeciWcs elsewhere. Breeding was highly synchronous, with no signiWcant diVerence in the breeding success between early and late breeders or between pairs breeding in diVerent habitats. We demonstrate for the Wrst time that the A-egg produced by the southern rockhopper penguin has, when alone, the same theoretical intrinsic potential to lead to a Xedged chick as the B-egg. In contrast, the hatching success and survival of the B-chick was similar when alone or in a two-egg clutch.

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Due to their restricted foraging range, flightless seabirds are ideal models to study the short-term variability in foraging success in response to environmentally driven food availability. Wind can be a driver of upwelling and food abundance in marine ecosystems such as the Southern Ocean, where wind regime changes due to global warming may have important ecological consequences. Southern rockhopper penguins (Eudyptes chrysocome) have undergone a dramatic population decline in the past decades, potentially due to changing environmental conditions. We used a weighbridge system to record daily foraging mass gain (the difference in mean mass of adults leaving the colony in the morning and returning to the colony in the evening) of adult penguins during the chick rearing in two breeding seasons. We related the day-to-day variability in foraging mass gain to ocean wind conditions (wind direction and wind speed) and tested for a relationship between wind speed and sea surface temperature anomaly (SSTA). Foraging mass gain was highly variable among days, but did not differ between breeding seasons, chick rearing stages (guard and crèche) and sexes. It was strongly correlated between males and females, indicating synchronous changes among days. There was a significant interaction of wind direction and wind speed on daily foraging mass gain. Foraging mass gain was highest under moderate to strong winds from westerly directions and under weak winds from easterly directions, while decreasing under stronger easterly winds and storm conditions. Ocean wind speed showed a negative correlation with daily SSTA, suggesting that winds particularly from westerly directions might enhance upwelling and consequently the prey availability in the penguins' foraging areas. Our data emphasize the importance of small-scale, wind-induced patterns in prey availability on foraging success, a widely neglected aspect in seabird foraging studies, which might become more important with increasing changes in climatic variability.

Logger technology has revolutionised our knowledge of the behaviour and physiology of free-living animals but handling and logger attachments may have negative effects on the behaviour of the animals and their welfare. We studied southern rockhopper penguin (Eudyptes chrysocome) females during the guard stage in three consecutive breeding seasons (2008/09−2010/11) to evaluate the effects of handling and logger attachment on foraging trip duration, dive behaviour and physiological parameters. Smaller dive loggers (TDRs) were used in 2010/11 for comparison to larger GPS data loggers used in all three seasons and we included two categories of control birds: handled controls and PIT control birds that were previously marked with passive integrative transponders (PITs), but which had not been handled during this study. Increased foraging trip duration was only observed in GPS birds during 2010/11, the breeding season in which we also found GPS birds foraging further away from the colony and travelling longer distances. Compared to previous breeding seasons, 2010/11 may have been a period with less favourable environmental conditions, which would enhance the impact of logger attachments. A comparison between GPS and TDR birds showed a significant difference in dive depth frequencies with birds carrying larger GPS data loggers diving shallower. Mean and maximum dive depths were similar between GPS and TDR birds. We measured little impact of logger attachments on physiological parameters (corticosterone, protein, triglyceride levels and leucocyte counts). Overall, handling and short-term logger attachments (1–3 days) showed limited impact on the behaviour and physiology of the birds but care must be taken with the size of data loggers on diving seabirds. Increased drag may alter their diving behaviour substantially, thus constraining them in their ability to catch prey. Results obtained in this study indicate that data recorded may also not represent their normal dive behaviour.

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1. Anthropogenic changes in the marine environment and global climate change have led to population declines in several seabird species worldwide. Rockhopper penguins (Eudyptes chrysocome and Eudyptes moseleyi) have experienced a dramatic population decline, potentially linked to increasing sea surface temperatures (SST). Among Southern Ocean diving seabirds, rockhopper penguins typically occupy a low trophic level, and might therefore be expected to mirror climate-driven bottom-up changes to the food web sensitively and on a short time scale.2. Using passive integrated transponders, survival rates of adults in a colony of southern rockhopper penguins (E. chrysocome) on the Falkland Islands were monitored over five consecutive years. Mean annual survival rates were in the range 84 to 96%.3. These values are high compared with other crested penguin species and reflect the generally good conditions during the study period, when low SST prevailed. However, survival rates were lower in 2010, corresponding to very cold conditions. Curve fits showed a best-fit quadratic relationship between average SST anomaly and survival rates for the present data, as well as for a data set including two additional years from a different study at Staten Island.4. Results of this study suggest that rockhopper penguins survive best at SSTs that are lower than the average of the last four decades. In accordance with previously observed rockhopper penguin population declines, the present data suggest that rockhopper penguins are highly sensitive to changes in SST and their effects on the food web, a worrying perspective in times of global climate change. It seems likely that these changes could, in the long term, also affect population trends of other seabird species with similar ecological preferences.5. The most promising conservation approach should aim at enhancing ecosystem resilience, mainly by reducing industrial fishing and oil exploitation. This would allow the currently over-exploited fish and squid stocks to recover, offering larger food resources to seabirds and other vertebrate species.