The University Record, November 26, 1997

Not quite Hitchcock, but the crows are back

This crow may soon have its behavior modified, encouraging it to seek a roosting site away from Central Campus. Photo by Bob Kalmbach


By Joanne Nesbit
News and Information Services

They're back. Those cawing Corvidae have returned to Central Campus, where from dusk to dawn they stake claim to lofty branches, primarily along State Street. These perennial black-feathered, raucous-voiced visitors, who seemingly find security and warmth in the trees near Angell Hall and the Diag, have been the subject of fables, myth, Native American lore, and the ire of those who traverse the splattered sidewalks beneath their perches.

In her doctoral research on Ann Arbor's crows, Cynthia Sims Parr, a visiting scholar at the Museum of Zoology and a postdoctoral fellow at Seoul National University, found that the corvus brachyrhynchos, eastern American crow, can number into multiple thousands as they circle the Central Campus just before dusk, landing on the uppermost branches of the tallest trees in the area. Parr believes that after feeding in the county's surrounding cornfields, landfills, dumpsters and feeders intended for other species during the day, the crows are looking for a warm and secure place to spend the night. The buildings emit warmth, Parr says, and the lights around Angell Hall give the crows an advantage when looking for predators.

Parr's research concentrated on the vocalization of these agrarian pests and urban nuisances. Their cawing or cooing is used to attract more crows in order to "mob" a potential predator, "chat" with neighbors, or "soothe" their own offspring. Besides affording more eyes to watch for predators, the advantages of being in a large flock include greater numbers to locate additional food sources and more successful breeding.

"In the Ann Arbor population," Parr says, "breeding groups appear to include two breeders and up to five of their adult offspring of various ages and both sexes." She theorizes that crows, well-known omnivores and one of the most intelligent bird species, may stay at home so long because they require extended learning periods to become expert in procuring food from relatively novel sources. Another possible benefit of adult offspring remaining with the family is the help they give their parents, not only in caring for younger siblings, but also reducing the risk and energy expenditure of the breeding parents by participating in mobbing intruders and predators. This reduction in risk and energy may then improve the parents' future chances for additional breeding success.

Yes, the thousands of crows on the Central Campus are considered a problem, says Dale Hodgson, pest management specialist in Building Services. But they are more an aesthetic problem than one of health or safety, he says. Behavior modification seems to be the key to dislodging the crows from the comfort and security they find around Angell Hall and the Diag. The idea of hanging balloons or fake owls in the trees has been bypassed, Hodgson says, because the crows are so urbanized that they are used to such visual distractions.

The crows use the area around Inglis House and Forest Hill Cemetery as a staging area before making their move into the core of the campus. One option to solving the roosting problem is to disturb that staging routine by introducing loud noises and thereby changing the flight and roosting patterns. Among the options being considered is creating a new roosting site in Nichols Arboretum. Hodgson says the method selected to remove the crows from their accustomed roosting sites on the Central Campus will be one that does not harm the birds.