Ask SIB – More Birds Mobbing

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
Red-winged Blackbird mobbing Great Blue Heron, by Larry deWitt;

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”