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.
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