Novel foraging in the swash zone on Pacific sand crabs (Emerita analoga, Hippidae) by mallards

Wilson Journal of Ornithology
By: , and 



Mallards (Anas platyrhynchos) have been observed foraging on intertidal Pacific sand crabs (Hippidae, Emerita analoga) in the swash zone of sandy beaches around Coal Oil Point Reserve, California, and several other beaches on the west coast since at least November 2010. Unlike foraging shorebirds, Mallards do not avoid incoming swashes. Instead, the incoming swash lifts and deposits them down the beach. Shorebirds and diving ducks commonly feed on sand crabs, but sand crabs appear to be a novel behavior and food source for Mallards. Previous surveys of beaches did not report foraging Mallards on regional beaches, whereas foraging Mallards were common in contemporary (recent) surveys and anecdotal reports. Observations of this potentially new behavior were separated by as much as 1,300 km, indicating that this was not a local phenomenon. Mallards foraged singly, in pairs, and in flocks. An expansion of diet to sand crabs carries risks of exposure to surf, human disturbance, high salt intake, and transmission of acanthocephalan and trematode parasites for Mallards but has the benefit of providing a dependable source of animal protein.
Publication type Article
Publication Subtype Journal Article
Title Novel foraging in the swash zone on Pacific sand crabs (Emerita analoga, Hippidae) by mallards
Series title Wilson Journal of Ornithology
DOI 10.1676/12-141.1
Volume 125
Issue 2
Year Published 2013
Language English
Publisher Wilson Ornithological Society
Publisher location Lawrence, KS
Contributing office(s) Western Ecological Research Center
Description 4 p.
First page 423
Last page 426
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