David M. Larson
Herring Gull with clam. Photograph by Andrew Cannizzaro (CC BY 2.0).
Anyone who lives along our coast has seen the phenomenon—gulls find a clam, fly up, drop their prey, and swoop down to retrieve the edibles from the usually shattered bivalve. But haven’t you wondered, “How did they figure that out?” and “Did they learn that technique or is it innate?”
There is considerable literature on feeding behavior in gulls, including The Herring Gull’s World by Niko Tinbergen (1953), one of the true classics of bird behavioral studies. As one might expect, juvenile gulls are less efficient at foraging and feeding than are adults. Juveniles may be less skilled at picking feeding areas, may be kept away from high-quality feeding areas by adults, may be less able to discriminate optimal prey items, or may be less efficient at foraging due to inexperience or physical or social deficits. Large gulls are identifiable in age class until reaching maturity at four years, so age-related changes in foraging have been well documented. Recently, Cristol et al. (2017) reported on their studies into the reasons for age-related foraging differences in American Herring Gulls (Larus argentatus) feeding on Atlantic rangia wedge clams (Rangia cuneata), primarily in a shallow coastal estuary in Virginia. Follow-up observations were conducted at a boat landing on Chesapeake Bay.
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