Active breeding seabirds prospect alternative breeding colonies.

Compared to other animal movements, prospecting by adult individuals for a future breeding site is commonly overlooked. Prospecting influences the decision of where to breed and has consequences on fitness and lifetime reproductive success. By analysing movements of 31 satellite- and GPS-tracked gull and tern populations belonging to 14 species in Europe and North America, we examined the occurrence and factors explaining prospecting by actively breeding birds. Prospecting in active breeders occurred in 85.7% of studied species, across 61.3% of sampled populations. Prospecting was more common in populations with frequent inter-annual changes of breeding sites and among females. These results contradict theoretical models which predict that prospecting is expected to evolve in relatively predictable and stable environments. More long-term tracking studies are needed to identify factors affecting patterns of prospecting in different environments and understand the consequences of prospecting on fitness at the individual and population level.

Wintering in the Western Subarctic Pacific Increases Mercury Contamination of Red-Legged Kittiwakes.

Marine methylmercury concentrations vary geographically and with depth, exposing organisms to different mercury levels in different habitats. Red-legged kittiwakes (Rissa brevirostris), a specialist predator, forage on fish and invertebrates from the mesopelagic zone, a part of the ocean with elevated methylmercury concentrations. We used kittiwakes as bioindicators of MeHg concentrations in remote mesopelagic systems by examining how wintering distribution and habitat affected kittiwakes' mercury exposure. In 2011-2017, we sampled winter-grown feathers on St. George Island, Alaska, from birds equipped with geolocation loggers. We measured total mercury (THg) and nitrogen stable isotopes in nape and head feathers grown during winter, respectively. THg concentration of kittiwake nape feathers averaged 4.61 ± 0.97 µg/g dry weight. Hierarchical cluster analysis was used to classify winter habitats with remotely sensed environmental variables along each bird's track. Five habitat clusters were identified. Birds that spent more time in the Western Subarctic Gyre and those that wintered further south had elevated THg concentrations. In contrast to THg, trophic level varied annually but did not show strong spatial patterns. Our results documented spatial variability in THg exposure based on the oceanic wintering locations of red-legged kittiwakes and highlight their use as a bioindicator of MeHg across ocean basins.

Body size affects individual winter foraging strategies of thick-billed murres in the Bering Sea.

Foraging and migration often require different energetic and movement strategies. Though not readily apparent, constraints during one phase might influence the foraging strategies observed in another. For marine birds that fly and dive, body size constraints likely present a trade-off between foraging ability and migration as smaller bodies reduce flight costs, whereas larger bodies are advantageous for diving deeper. This study examines individual wintering strategies of deep diving thick-billed murres (Uria lomvia) breeding at three colonies in the south-eastern Bering Sea: St Paul, St George and Bogoslof. These colonies, arranged north to south, are located such that breeding birds forage in a gradient from shelf to deep-water habitats. We used geolocation time-depth recorders and stable isotopes from feathers to determine differences in foraging behaviour and diet of murres during three non-breeding periods, 2008-2011. Body size was quantified by a principal component analysis (wing, culmen, head+bill and tarsus length). A hierarchical cluster analysis identified winter foraging strategies based on individual movement, diving behaviour and diet (inferred from stable isotopes). Structural body size differed by breeding island. Larger birds from St Paul had higher wing loading than smaller birds from St George. Larger birds, mainly from St Paul, dove to deeper depths, spent more time in the Bering Sea, and likely consumed higher trophic-level prey in late winter. Three winter foraging strategies were identified. The main strategy, employed by small birds from all three breeding colonies in the first 2 years, was characterized by high residency areas in the North Pacific south of the Aleutians and nocturnal diving. In contrast, 31% of birds from St Paul remained in the Bering Sea and foraged mainly during the day, apparently feeding on higher trophic-level prey. Throat feather stable isotopes indicated that individuals exhibited flexibility in the use of this colony-specific foraging strategy. The third strategy only occurred in 2010/2011, when birds dove more and deeper, suggesting limited prey resources. Foraging strategies partitioned with respect to annual differences, presumably in response to shifts in distribution of prey, and were linked to body size. The presence of a colony-specific wintering strategy suggests the potential for overwinter survival differences between these populations.

Health evaluation of free-ranging Humboldt penguins (Spheniscus humboldti) in Peru.

As part of ongoing ecological studies of Humboldt penguins (Spheniscus humboldti) at Punta San Juan, Ica Department, Peru, health surveys were conducted in November 1992, 1993, and 1994. In the three surveys, 98 birds in total were handled for examination, and blood was collected for laboratory analysis from 90 of these birds. All birds seemed to be in good condition. Body weights of females were significantly lower in 1994 than in the other years. Fleas (Parapsyllus humboldti) and ticks (Ornithodoros amblus) were found on the penguins and in their nests. Females had significantly higher plasma calcium and phosphorus levels, and they had lower weights than males. No other differences were found between the sexes. Hematology, plasma chemistries, and plasma mineral levels varied between years. Positive antibody titers for Chlamydophila psittaci (62%), avian adenovirus (7%; 1994 only), paramyxovirus-2 (7%; 1993 only), and Salmonella Pullorum (7%) were found. Plasma chemistry and mineral levels differed between individuals testing positive vs. negative on serologic tests for avian adenovirus and Salmonella Pullorum. Serologic tests for antibodies to avian influenza A virus, avian encephalomyelitis virus, infectious bronchitis virus, avian reovirus, duck viral enteritis virus, equine encephalitis (eastern, western, and Venezuelan) viruses, infectious bursal disease virus, infectious laryngotracheitis virus, Aspergillus sp., and paramyxovirus-1 and -3 were negative. All chlorinated pesticide and polychlorinated biphenyl analyses were below detectable limits.

Wintering North Pacific black-legged kittiwakes balance spatial flexibility and consistency.

BACKGROUND: Marine environments are inherently dynamic, yet marine predators are often long-lived and employ strategies where consistency, individual specialization, routine migrations, and spatial memory are key components to their foraging and life-history strategies. Intrinsic determinates of animal movements are linked to physiological and life-history traits (e.g. sex, colony, experience), while extrinsic influences occur as the result of an animal's interactions with either other animals or the environment (e.g. prey availability, weather, competition). Knowledge of the factors affecting animal movements is critical to understand energetic bottlenecks and population dynamics. Here, we attempt to understand the interaction of some of these factors on the winter distributions of a surface-feeding seabird in the North Pacific. Between 2008 and 2011, we tracked 99 black-legged kittiwakes breeding at St. Paul and St. George in the Pribilof Islands, Alaska using geolocation loggers. We tested for colony and sex differences in winter distributions, and individual spatial fidelity over two consecutive winters of 17 individuals. Then we linked tracking data to associated environmental conditions as proxies of prey availability (e.g. sea surface temperature, mesoscale eddies, chlorophyll a, and wind) to understand their influence on kittiwake space use at an ocean basin scale. RESULTS: Black-legged kittiwakes from both Pribilof Islands primarily wintered in pelagic sub-arctic waters, however, distributions spanned seven ecoregions of the North Pacific. There was a high degree of similarity in area use of birds from the two closely situated colonies and between sexes. Birds tracked for two consecutive years showed higher fidelity to wintering areas than occurred at random. Annual changes were apparent, as distributions were further north in 2009/10 than 2008/09 or 2010/11. This occurred because 70 % of birds remained in the Bering Sea in the fall of 2009, which corresponded with lower October sea surface temperatures than the other two years. CONCLUSIONS: Although individuals returned to wintering areas in consecutive years, our results suggest that under current conditions individual black-legged kittiwakes have a high capacity to alter winter distributions.

Foraging responses of black-legged kittiwakes to prolonged food-shortages around colonies on the Bering Sea shelf.

We hypothesized that changes in southeastern Bering Sea foraging conditions for black-legged kittiwakes (Rissa tridactyla) have caused shifts in habitat use with direct implications for population trends. To test this, we compared at-sea distribution, breeding performance, and nutritional stress of kittiwakes in three years (2008-2010) at two sites in the Pribilof Islands, where the population has either declined (St. Paul) or remained stable (St. George). Foraging conditions were assessed from changes in (1) bird diets, (2) the biomass and distribution of juvenile pollock (Theragra chalcogramma) in 2008 and 2009, and (3) eddy kinetic energy (EKE; considered to be a proxy for oceanic prey availability). In years when biomass of juvenile pollock was low and patchily distributed in shelf regions, kittiwake diets included little or no neritic prey and a much higher occurrence of oceanic prey (e.g. myctophids). Birds from both islands foraged on the nearby shelves, or made substantially longer-distance trips overnight to the basin. Here, feeding was more nocturnal and crepuscular than on the shelf, and often occurred near anticyclonic, or inside cyclonic eddies. As expected from colony location, birds from St. Paul used neritic waters more frequently, whereas birds from St. George typically foraged in oceanic waters. Despite these distinctive foraging patterns, there were no significant differences between colonies in chick feeding rates or fledging success. High EKE in 2010 coincided with a 63% increase in use of the basin by birds from St. Paul compared with 2008 when EKE was low. Nonetheless, adult nutritional stress, which was relatively high across years at both colonies, peaked in birds from St. Paul in 2010. Diminishing food resources in nearby shelf habitats may have contributed to kittiwake population declines at St Paul, possibly driven by increased adult mortality or breeding desertion due to high foraging effort and nutritional stress.

Prey patch patterns predict habitat use by top marine predators with diverse foraging strategies.

Spatial coherence between predators and prey has rarely been observed in pelagic marine ecosystems. We used measures of the environment, prey abundance, prey quality, and prey distribution to explain the observed distributions of three co-occurring predator species breeding on islands in the southeastern Bering Sea: black-legged kittiwakes (Rissa tridactyla), thick-billed murres (Uria lomvia), and northern fur seals (Callorhinus ursinus). Predictions of statistical models were tested using movement patterns obtained from satellite-tracked individual animals. With the most commonly used measures to quantify prey distributions--areal biomass, density, and numerical abundance--we were unable to find a spatial relationship between predators and their prey. We instead found that habitat use by all three predators was predicted most strongly by prey patch characteristics such as depth and local density within spatial aggregations. Additional prey patch characteristics and physical habitat also contributed significantly to characterizing predator patterns. Our results indicate that the small-scale prey patch characteristics are critical to how predators perceive the quality of their food supply and the mechanisms they use to exploit it, regardless of time of day, sampling year, or source colony. The three focal predator species had different constraints and employed different foraging strategies--a shallow diver that makes trips of moderate distance (kittiwakes), a deep diver that makes trip of short distances (murres), and a deep diver that makes extensive trips (fur seals). However, all three were similarly linked by patchiness of prey rather than by the distribution of overall biomass. This supports the hypothesis that patchiness may be critical for understanding predator-prey relationships in pelagic marine systems more generally.

Sex differences in razorbill Alca torda parent-offspring vocal recognition.

We investigated differences in parent-offspring vocal recognition between males and females in a natural population of razorbills Alca torda, a long-lived and highly social species of auk (Family: Alcidae). Razorbills provide biparental care to their chicks while at the nest site, after which the male is the sole caregiver for an additional period at sea. Parent-offspring recognition in razorbills is most challenging once the chick becomes mobile, leaves the nest site and goes to sea with the male parent. It is during this period when selection pressure acting on recognition behaviour is expected to be strongest. As a result, we predicted that parent-offspring recognition would be better developed in the male parent, that is, show a paternal bias. To test this prediction we used vocal playback experiments conducted on breeding razorbills at the Gannet Islands, Labrador, Canada. We found (1) most positive responses to playbacks (vocal and phonotactic) occurred close to fledging, (2) males responded more to calls from their chicks than to calls from strange chicks, (3) females responded indifferently to calls from their own or strange chicks and (4) chicks responded more to calls from their male parent than to calls from other adult males. The results provide clear evidence of mutual vocal recognition between the male parent and the chick but not between the female parent and the chick, supporting the prediction that parent-offspring recognition is male biased in this species. Such a bias could have important social implications for a variety of behavioural and basic life history traits such as cooperation and sex-biased dispersal.