Date: November 5, 2015
Source: Central Ornithology Publication Office
Gulls have learned to follow diving ducks and take the bottom-dwelling mussels that the ducks bring to the surface, a food source that would otherwise be inaccessible to them. Gulls are one of the most adaptable groups of birds, able to exploit a wide variety of food resources and respond to new opportunities, and a study forthcoming in The Auk: Ornithological Advances documents this previously unrecognized behavior in Herring Gulls (Larus argentatus) and Mew Gulls (Larus canus) on a brackish lagoon on the Germany-Poland border.
Ducks wintering on Szczecin Lagoon dive to the bottom to forage on zebra mussels, bringing clumps of mussels to the surface and regularly losing fragments in the process. To determine whether the gulls on the lagoon take advantage of this or if their presence while the ducks are foraging is only a coincidence, Dominik Marchowski of Szczecin University and his colleagues observed the behavior of the birds between October 2013 and November 2014, watching three species of duck--the Common Pochard (Aythya ferina), Tufted Duck (A. fuligula), and Greater Scaup (A. marila)--through spotting scopes. They recorded how intensely the ducks were foraging and whether any gulls were present, and they also collected gull pellets to confirm what they were eating.