Abstract: Skip to Next Section Little auks (Alle alle) are one of the most numerous seabird species in the world and feed primarily on copepods in arctic waters. Their high daily energy requirements leave them vulnerable to current changes in the arctic plankton community, where a smaller, less-profitable copepod species (Calanus finmarchicus) becomes increasingly abundant. Little auks have been estimated to require ?60,000 copepods per day, necessitating prey capture rates of ?6 copepods per second underwater. To achieve such performance, it has been suggested that little auks capture their prey by (non-visual) filter feeding. We tested this hypothesis by exposing little auks to varying copepod densities within a shallow experimental pool and filming their prey capture behaviour. At none of the copepod densities tested did birds filter feed. Instead, all birds captured copepods by what we identified as visually guided suction feeding, achieved through an extension of their sub-lingual pouch. Suction feeding is very common in fish and marine mammals, but to the best of our knowledge, this is the first time that it has been specifically identified in a seabird species. While presumably less efficient than filter feeding, this behaviour may allow little auks to foster higher resilience when facing the consequences of arctic climate change.

Abstract: Summary Wind is an important climatic factor for flying animals as by affecting their locomotion, it can deeply impact their life?history characteristics. In the context of globally changing wind patterns, we investigated the mechanisms underlying recently reported increase in body mass of a population of wandering albatrosses (Diomedea exulans) with increasing wind speed over time. We built a foraging model detailing the effects of wind on movement statistics and ultimately on mass gained by the forager and mass lost by the incubating partner. We then simulated the body mass of incubating pairs under varying wind scenarios. We tracked the frequency at which critical mass leading to nest abandonment was reached to assess incubation success. We found that wandering albatrosses behave as time minimizers during incubation as mass gain was independent of any movement statistics but decreased with increasing mass at departure. Individuals forage until their energy requirements, which are determined by their body conditions, are fulfilled. This can come at the cost of their partner's condition as mass loss of the incubating partner depended on trip duration. This behaviour is consistent with strategies of long?lived species which favoured their own survival over their current reproductive attempt. In addition, wind speed increased ground speed which in turn reduced trip duration and males foraged further away than females at high ground speed. Contrasted against an independent data set, the simulation performed satisfactorily for males but less so for females under current wind conditions. The simulation predicted an increase in male body mass growth rate with increasing wind speed, whereas females' rate decreased. This trend may provide an explanation for the observed increase in mass of males but not of females. Conversely, the simulation predicted very few nest abandonments, which is in line with the high breeding success of this species and is contrary to the hypothesis that wind patterns impact incubation success by altering foraging movement.