Carryover effects of winter mercury contamination on summer concentrations and reproductive performance in little auks.

Many animals migrate after reproduction to respond to seasonal environmental changes. Environmental conditions experienced on non-breeding sites can have carryover effects on fitness. Exposure to harmful chemicals can vary widely between breeding and non-breeding grounds, but its carryover effects are poorly studied. Mercury (Hg) contamination is a major concern in the Arctic. Here, we quantified winter Hg contamination and its carryover effects in the most abundant Arctic seabird, the little auk Alle alle. Winter Hg contamination of birds from an East Greenland population was inferred from head feather concentrations. Birds tracked with Global Location Sensors (GLS, N = 28 of the total 92) spent the winter in western and central North Atlantic waters and had increasing head feather Hg concentrations with increasing longitude (i.e., eastward). This spatial pattern was not predicted by environmental variables such as bathymetry, sea-surface temperature or productivity, and needs further investigation. Hg concentrations in head feathers and blood were strongly correlated, suggesting a carryover effect of adult winter contamination on the consequent summer concentrations. Head feather Hg concentrations had no clear association with telomere length, a robust fitness indicator. In contrast, carryover negative effects were detected on chick health, as parental Hg contamination in winter was associated with decreasing growth rate of chicks in summer. Head feather Hg concentrations of females were not associated with egg membrane Hg concentrations, or with egg volume. In addition, parental winter Hg contamination was not related to Hg burdens in chicks' body feathers. Therefore, we hypothesise that the association between parental winter Hg exposure and the growth of their chick results from an Hg-related decrease in parental care, and needs further empirical evidence. Our results stress the need of considering parental contamination on non-breeding sites to understand Hg trans-generational effects in migrating seabirds, even at low concentrations.

Year-round at-sea movements of fairy prions from southeastern Australia.

Effective conservation assessments require detailed information of species' ecological niches during the whole annual cycle. For seabirds, this implies investigating the at-sea distribution and foraging behaviour during both the breeding and non-breeding periods. However, until recently, collecting information about small species has been precluded by the excessive size of the required devices. This lack of knowledge is exacerbated in the case of polytypic genera with species sharing very similar appearance and behaviour, such as the super-abundant prions (Pachyptila spp.). The present study investigates the year-round at-sea distribution and foraging ecology of the fairy prion (Pachyptila turtur) in southeastern Australia. Miniaturized GPS loggers during the breeding season and geolocators (GLS) during the non-breeding period were used over 4 consecutive years (2017-2021), with results that highlight the importance of the continental shelf-edge waters for fairy prions throughout the year. In addition, contrary to previous assumptions, the GLS data revealed an unsuspected post-breeding migration to the waters south of Australia, during which individuals probably undergo a rapid moult of flight feathers. Understanding the at-sea distribution and ecology of prions during the whole annual cycle will be fundamental to their conservation as it can reveal species- or population-specific threats that have been overlooked because of their status as abundant species.

Foraging niche overlap during chick-rearing in the sexually dimorphic Westland petrel.

Most Procellariform seabirds are pelagic, breed in summer when prey availability peaks, and migrate for winter. They also display a dual foraging strategy (short and long trips) and sex-specific foraging. The Westland petrel Procellaria westlandica, a New Zealand endemic, is one of the rare seabirds breeding in winter. Preliminary findings on this large and sexually dimorphic petrel suggest a foraging behaviour with no evidence of a dual strategy, within a narrow range and with shared areas between sexes. To investigate further this unusual strategy, the present study determined the fine-scale at-sea behaviours (global positioning system and accelerometer data loggers) and trophic niches (stable isotopes in whole blood) of chick-rearing individuals (16 males and 13 females). All individuals foraged on the shelf-slope of the west coast of New Zealand's South Island with short, unimodal trips. Both sexes foraged at similar intensity without temporal, spatial or isotopic niche segregation. These findings suggest the presence of a winter prey resource close to the colony, sufficient to satisfy the nutritional needs of breeding without increasing the foraging effort or intra-specific competition avoidance during winter. Additional data are needed to assess the consistency of foraging niche between the sexes and its reproductive outcomes in view of anticipated environmental changes.

Human exploitation assisting a threatened species? The case of muttonbirders and Buller's albatross.

Albatrosses are flexible and adaptable predators, relying on live prey as well as carrion. Use of predictable food sources and reliance on human-produced resources are well-known trait in long-range feeders like albatrosses and petrels. Breeding Buller's albatrosses studied at Solander I. (Hautere), New Zealand fed their chicks the remains of sooty shearwater juveniles (titi in Maori), which are harvested from nearby muttonbirding sites. Evidence of this food type was found at over 10% of nests examined, and 17-40% birds that were fitted with GPS loggers visited muttonbirding sites in this and previous studies. Muttonbirding is a traditional practice that has continued for centuries, with up to 120 tonnes of offal discharged to the sea annually during the present day harvest. It coincides with the energetically-demanding early chick period for the albatrosses. Our finding suggests that the offal may be an important, but overlooked element in the albatross diet. As an important supplementary food for the albatrosses it is likely to have contributed to the 3% per annum growth of their populations since the first comprehensive population surveys in 1969.

Influence of oceanographic structures on foraging strategies: Macaroni penguins at Crozet Islands.

BACKGROUND: In the open ocean, eddies and associated structures (fronts, filaments) have strong influences on the foraging activities of top-predators through the enhancement and the distribution of marine productivity, zooplankton and fish communities. Investigating how central place foragers, such as penguins, find and use these physical structures is crucial to better understanding their at-sea distribution. In the present study, we compared the travel heading and speed of the world's most abundant penguin, the Macaroni penguin (Eudyptes chrysolophus), with the distribution of surface physical structures (large-scale fronts, eddies and filaments). RESULTS: The study was performed during December 2012 in the Crozet Archipelago (46.42° S; 51.86° E), South Indian Ocean. Six males at incubation stage were equipped with GPS loggers to get their trajectories. We used Eulerian and Lagrangian methods to locate large-scale fronts, mesoscale eddies (10-100 km) and part of the sub-mesoscale structures (<10 km, filaments) at the surface of the ocean. By comparing the positions of birds and these structures, we show that Macaroni penguins: i) target the sub Antarctic Front; ii) increase their foraging activity within a highly dynamic area, composed of eddy fields and filamentary structures; and iii) travel in the same direction as the predominant currents. CONCLUSIONS: We show that penguins adjust their travel speed and movement during their whole trips in relation with the oceanographic structures visited. At a large scale, we hypothesize that Macaroni penguins target the sub Antarctic Front to find profitable patches of their main prey. At finer scale, Macaroni penguin may adopt a horizontal drifting behavior in strong currents, which could be a way to minimize costs of displacement.