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Sunday, July 7, 2013

Crab for dinner

While watching a small group of Willets (Tringa semipalmata) feeding in Bodega Harbor late this afternoon, I was a little surprised at how often they were catching prey.  It seemed like every few seconds one would come up with a small crab.  And it was very easy to scan the group and to see several birds with crabs at one time.

Here are two close-ups of birds with crabs in their bills.  Do you have thoughts about the type of crab?

I think these are small Dungeness Crabs.  The carapace seems fairly rounded and lacks prominent spines.  A Bay Shore Crab  (Hemigrapsus oregonensis) would have a more rectangular carapace and a European Green Crab (Carcinus maenas) would have visible spines.  But let me know if you agree or disagree.

The Birds of North America account describes Willets eating crabs like this: "Grasps crabs by leg and shakes until body flies off, then eats leg and process repeated until legless carapace is swallowed whole."

The next three images illustrate this behavior.  In the first photo, look for the crab leg in the Willet's bill and the crab that's just been shaken off to the left.

The next picture shows a crab with half of its legs missing.   

The final image is a bird with a mostly legless crab that it's just about to swallow.

It's interesting to think about how this record year for juvenile Dungeness Crabs may translate into quite a bit of energy for Willets and other animals that feed on the crabs!

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