Friday, November 16, 2012

Catch Me If You Can – The American Oystercatcher

Originally published on Audubon Guides on October 1st, 2012
Catching an oyster only seems difficult to me if you’re tossing one around with your kid in your backyard. For a predator the difficulty is not chasing one down but prying one apart once they’ve located it. The two sides of the bivalve’s shell are bound together by an adductor that protects them from prying intruders. Hopefully.

Considering the difficulty of which it is to open an oyster for a human, the American Oystercatcher (Haematopus palliates) is a devastating effective predator of mollusks of all sorts. Juvenile oystercatchers are taught certain techniques by their parents that make a quick meal of mollusks. They are aided by a stout, powerful bill with triangular shaped mandibles in cross section that are reinforced in such a way that they will not bend easily when attacking prey.
American Oystercatcher © Pete Corradino
One method taught, known as “stabbing”, is to sneak up on the oyster while the shell is open even the slightest, stab at the adductor and break the shell open, exposing the meal inside. The second method, “hammering”, is to pry the oyster from the oyster bed or other place of attachment and then use the bill to shatter a hole in the shell. They can then break the adductor and eat their meal.
American Oystercatcher © Pete Corradino
In addition to oysters they feed on a variety of shellfish, crabs and tube worms. Crabs are flipped on their back and stabbed to death with the bill. To locate tube worms, sensitive nerve endings in the bill allow them to sense prey as they probe the tidal flats.
A Willet attempts to drive off an Oystercatcher © Pete Corradino
Occasionally confused with the Black Skimmer (Rynchops niger), the oystercatcher’s mandibles are equal in length compared to the skimmer’s disproportionate upper and lower mandibles. The oystercatcher has a black head, white belly, and sturdy pink legs.

As willets and sandpipers scooted along the surf, the oystercatcher above methodically probed the sand for lunch, ignoring the beachgoers. When you’re a stabber or a hammerer who’s going to mess with you?

1 comment:

  1. So fun to watch them in the surf! Thanks for posting!