Seabirds foraging at floating seaweeds in the Northeast Atlantic

The influence of floating seaweed patches on the distribution and behaviour of seabirds was investigated using the European Seabirds At Sea database (ESAS). The percentage of observations that seabirds were observed with floating seaweed differed among species, depending on the mode of foraging. The results indicate that surface feeding species that make shallow dives (terns and Red-breasted Mergansers Mergus serrator) benefit most from the presence of floating seaweeds and their associated macro- and ichthyofauna. Species hunting for pelagic and bottom-dwelling prey (divers, Guillemots Uria aalge, Razorbills Alca torda, Puffins Fratercula arctica, Gannets Sula bassana and Cormorants Phalacrocorax carbo), and especially benthos feeders (Common Scoters Melanitta nigra and Eiders Somateria mollissima) were frequently seen in association with floating seaweeds, while opportunists and scavengers like gulls and skuas were recorded on few occasions. Petrels and shearwaters (surface-seizing, pursuit-plunging, pursuit-diving) were seldomly seen in association with floating seaweeds. The most common behavioural activities of the birds associated with floating seaweed were found to be surface pecking, actively searching, and pursuit plunging.