Helping behavior can vary for corvid family

Last week’s column about crows proved to be popular and garnered a few responses from readers. One woman had a question about the helping behavior displayed by crows – young birds from the previous year have been found to help their parents feed and raise new broods.

“Is this behavior common to all the corvids? Ravens for example?” she asked.

This was an excellent question and a great topic for another column. I began researching the topic immediately.

Considering that several members of the corvid family – which includes jays, magpies, crows, and ravens – have been found to exhibit helping behavior in raising young, I thought it a good possibility that ravens would, too. But in this I was surprised.

Mated pairs of ravens have been observed to be accompanied by a third bird, but in most cases the relationships between the birds was not able to be established. In one instance, according to W.I. Boarman and B. Heinrich in the “Birds of North America” species account on the common raven, a juvenile from a previous brood was observed guarding nestlings while the parents foraged for food. This was the only definite record of a young bird helping its parents in the raising of another brood.

Ravens are historically known to be very wary of humans, although this seems to be changing. Researchers have documented that they react to humans approaching their nest site while still a half-mile away. It seems logical to conclude that this behavior might obscure some details of their family life; perhaps additional study and observation will tell.

The variation in helping behavior and cooperative breeding among members of the corvid family is fascinating. For example, there seems to be some dispute that our familiar blue jays engage in helping behavior. Although there have been some observations of helpers at nests, the BNA species account on the blue jay concludes that “the ‘help’ afforded by the extra-pair bird seemed to be either infrequent, clandestine, or unwanted by one or both members of the breeding pair. Other researchers have watched blue jay nests for many hours yet have seen no evidence of cooperative breeding.”

The BNA concludes that this lack of cooperation and helping behavior may be related to the jays’ habitat needs: they are habitat “generalists,” highly migratory and able to breed successfully in a variety of habitats. (I still can’t help but wonder why they’d turn down a “babysitter,” though).

“The Sibley Guide to Bird Life and Behavior,” nicely encapsulates cooperative breeding systems in other corvids. In contrast to the generalist blue jay, the Florida scrub jay is a habitat specialist in the extreme. They are closely tied to relict, fire-maintained Florida scrub habitats which are becoming increasingly fragmented. These jays are extremely nonmigratory and will not seek to colonize distant scrub habitats. They employ an elaborate helping system where many young of one breeding pair assist in raising each brood, but in many cases do not go on to mate and produce young themselves.

Yet another system is seen with Mexican jays. Several pairs may have nests within the group’s territory, but the young in the respective nests may not be the young of the pair attending the nest. Several jays may feed young from several nests at once, and once the nestlings fledge they are fed by all of the adults in the group.

Interestingly, Mexican jays rely on pine-oak-juniper woodlands in the mountains of central and northern Mexico, as well as similar mountain habitats in Arizona, New Mexico, and western Texas. Like the Florida scrub jay, the Mexican also is nonmigratory; young birds seldom leave the group they were born into.

The query of whether ravens and other corvids exhibit helping behavior opened the door to fascinating insights. Thanks for the great question!

Chris Corio, a volunteer at Fields Pond Audubon Center in Holden, can be reached at fieldspond@juno.com