Month: May 2021

Question:

Hi, Today I was walking not far from a pond with high reeds.  A big heron was standing on the ground minding his own business when suddenly a red wing blackbird exploded out of the reeds and attacked the heron.  The big guy took off  and the red wing kept after him for twenty or thirty yards.  I assume the red wing was protecting a nest but do heron eat bird chicks?

Andy Allen, SIB Member

Answer:

This interesting observation contains two parts based on the behavior of each bird. The Great Blue Heron is an opportunistic feeder and will eat anything it can get down its throat. This would presumably include Red-winged Blackbirds. Red-winged Blackbirds tend to be an aggressive species defending a territory against other Red-winged Blackbird and occasionally against predators. A male Red-winged Blackbird defends a territory as opposed to a mate. It is not uncommon for a strong male to hold a highly desirable territory which attracts numerous females. Therefore, the bird you saw chasing the heron was not defending a particular nest, but driving the bird from his territory and presumably his harem of females.

Mobbing, the behavior of chasing away a potential predator is a common behavior among many bird species. Is it innate or learned? I don’t believe anyone has studied the Red-winged Blackbird’s interactions. A surreptitious study by Konrad Lorenz and detailed in his book King Solomon’s Ring details how Rooks, a European species of crow, which he fed by hand, instinctively attacked his hand when he was holding a limp black object (similar to a dead Rook).

He tested this behavior on captive birds and learned that after the bird instinctively attached something holding a limp black object on three occasions did it learn to always attack that object. The final piece of the puzzle is once a bird learned to attack an object, it taught its progeny to attack that object even if they never saw the object holding something limp and black. For the Rooks, the behavior is both instinctive and learned. Maybe it is similar with the Red-winged Blackbird as they have been documented attacking tractors, cows, and horses, all things that might intrude into the birds habitat.

Bob Mercer, SIB’s “Resident Naturalist”

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

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”