One of my kiddos, born near the Chesapeake Bay, was our family's primary driver to 'get into birds'. This kiddo loved birds from a young age and always wanted to know which bird we could see and hear.
Because of this personal connection, I chose to look at the Christmas Bird Count from the Chesapeake Bay in 2003. The Chesapeake Bay is known for their famous Blue Crab, and the health of the blue crab is important in annual bay studies.
What's more fun than a little predation? The center of the Chesapeake Bay Christmas Bird Count is nearly all birds that thrive in the water. I looked up whether each bird was likely to eat blue crab in winter in the Cheseapeake Bay; for some species, I had to use some judgement on what 'some small crustaceans' might mean on its diet, but others are known crab munchers.
I did not realize this, but the vast majority of blue crab predation is cannabalism. Scientists estimate that more than 90% of juvenile blue crab predation is due to other crabs. While I'm focused here on which birds might, might, eat a blue crab, other blue crabs will definitely eat some blue crab