Agonistic interactions and vocalizations among Procellariiformes in multi-species feeding aggregations, observed through bird-borne cameras.

Marine predators frequently aggregate at food sources, where interactions can range from cooperative group hunting to interference competition for resources. To investigate interactions at feeding aggregations among procellariiforms, we equipped wandering albatrosses Diomedea exulans with video cameras, collecting 43 hours of footage from 22 individuals. Cameras from eight birds recorded feeding aggregations, capturing a total of 62 minutes of footage (2.7% of observations). All events involved multiple species, including other wandering albatrosses, sooty albatrosses Phoebetria spp., giant petrels Macronectes spp., white-chinned petrels Procellaria aequinoctialis and smaller petrels (prions Pachyptila spp., blue petrels Halobaena caerulea, gadfly petrels Pterodroma spp. and storm petrels Oceanitidae). As in terrestrial bird assemblages, access to food was largely regulated by the size of competing individuals. The presence of other wandering albatrosses influenced interactions, with agonistic interactions in multi-species associations (intimidation postures, strikes and fights) observed only in events involving more than one wandering albatross (four of eight events). These interactions were accompanied by vocalizations. We identified five types of vocalizations from four individuals based on acoustic structure (n = 84 vocalizations). Intimidation postures were frequently accompanied by modulated vocalizations, indicating a combined visual-acoustic threat display. High-pitched screams, though rare, were also associated with agonistic interactions. These results contribute to a better understanding of foraging ecology and resource access in scavenging seabirds. This article is part of the theme issue 'Multi-predator feeding aggregations in pelagic waters'.