Ask SIB: Do Birds Cooperate to Chase off Predatory Birds?

Question: I saw something that that I thought interesting . We have a blue bird box and a Carolina Wren nest around 50 feet apart. A large Crow landed on the Bluebird box. Both the males attacked the crow to drive it off. Were they working together or as individuals? The Bluebird stood on the top of the box, the Wren on top of its nest. Chipped to each other and entered their nest. Were they communicating with each other?

Anonymous SIB Member
Crow mobbed by Baltimore Oriole in White Clay Creek State Park, Delaware.
Photo from Buffalo Bill Center of the West.

Answer: What a cool observation! Normally, it is a House Wren that occupies a bluebird box. House wren are very aggressive and will even destroy a bluebirds eggs if it can. 

So normally, bluebirds do not tolerate having a wren nest nearby, unless the nest opening is too small for the bluebird. This leads me to believe the birds were not cooperating. Normally, both birds work to drive away predators. Nest predation is a major challenge for birds and crows are notorious for feeding on baby birds. Both the bluebird and the wren don’t want a crow nearby. So both would be inclined to attack the crow regardless of what their neighbor does.
This brings us to the second part of your question. Since the bluebird naturally competes with a wren, I suspect that the “communication” you saw was neighbors grousing at each other as opposed to bragging about their ability to chase a crow.

Recognizing that crows are highly intelligent birds, I bet this will not be the last time they visit. I suspect the crow will work hard to access the known food source-baby bluebirds and wren-either directly from the nest or waiting until the babies fledge. This is one reason why, as soon as babies come off the nest, the parents try to get them as far away from the nest and as SIB’s “Resident Naturalist”quickly as they can. 

Bob Mercer, SIB’s “Resident Naturalist”

Author: sibirders

SEABROOK ISLAND BIRDERS / “watching, learning, protecting” Seabrook Island Birders (SIB) are residents, renters and guests of Seabrook Island, SC who have an interest in learning, protecting and providing for the well-being of the incredible variety of birds that inhabit Seabrook Island throughout the year.

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