During the last decade, a controversy has raged over what to do with certain tracts of land on the UCD campus. The pile of press clippings generated by the subject is almost as tall as the 9-inch bird that stands at the center of the furor: the burrowing owl.

Most readers of the Enterprise are familiar with the pros and cons of the debate, which reached boiling point last year. That was when the University administration took a site previously deemed an Open Space Reserve for burrowing owls, and turned it over to developers for student housing. Opposing them are biologists and environmentalists who point out that the burrowing owl is a short hop away from the endangered species list.

Somewhere in all the racket, the fascinating behavior and biology of the little bird has been lost. It turns out that burrowing owls have a lot to teach us about a mating system that is more complex than it appears - monogamy and the nuclear family. On the surface it's a simple story: one male, one female, and their brood. But look a little deeper, and it's a soap opera, as ecologist, Brenda Johnson, has discovered.

While a graduate student in the Department of Zoology, Johnson studied the burrowing owls on campus from 1985-1988 and has monitored the population since then.

Like others of their kind, burrowing owls live in pairs during the breeding season, with both parents feeding their young on insects and small rodents that they hunt at night. Unlike other owls, however, they live on the ground in burrows dug by rodents such as ground squirrels.

Their habitat promotes a certain gregariousness unusual for owls. Breeding pairs, although still territorial, are drawn together by concentrations of burrows, and neighbors are in plain view of each other. In other bird species, such conditions can really push the monogamy envelope by encouraging adultery, mixing up of eggs, and mingling of broods.

During the four breeding seasons that Johnson observed the birds, she saw hints of these trends in the burrowing owls. Males flirted with neighbors; females occasionally made surreptitious visits to nearby burrows, possibly to lay an egg in another bird's nest. Ornithologist have given this behavior the rather inelegant name of "egg-dumping". To confuse things even more, owlets that couldn't yet fly sometimes visited other burrows on foot and merged with the broods.

With all this going on, it seemed likely that at least some adults were unwitting foster parents, but it was impossible to know just how blurry parentage had become. Clearly the owls themselves weren't sure. Johnson observed two nests that had a ménage of three adults in attendance, all feeding the young.

To get to the bottom of things, Johnson turned to DNA. Of the 112 owls that she leg-banded for individual recognition, she obtained DNA, from blood samples, for 67 of them. Through laborious, time-consuming analyses she was able to determine who belonged to whom, genetically speaking.

It turned out that over a third of the adults were raising one or more olwets that weren't theirs. From the younger generation's perspective, a fifth of baby owls grew up with at least one foster parent. While the burrowing owls' breeding system looks monogamous on the surface, the underlying genetic picture is far more complicated.

Research on other species has come up with similar findings. The extent to which "true" monogamy persists will vary, and studies like Johnson's can help us understand how it evolved. Of more immediate importance is the relevance of this work to understanding the behavior and genetics of dwindling populations. For example, Johnson's DNA analyses showed that the Davis burrowing owls are relatively inbred, possibly because young animals find it hard to disperse. There's nowhere left to go. If developers haven't paved over their homes, then farmers have killed off their burrow-makers, the ground squirrels.

Since her initial study, Johnson, who is now with UCD's Center for Ecological Health Research, has shown that between 1981 and 1991, the population of owls on campus plummeted to one adult. Several factors probably contributed to the crash, including habitat loss, the long drought, and the big '90 - '91 freeze. The good news is that empty habitat, if safe-guarded, can be re-colonized, and in the last few years, burrowing owls have been seen on campus in places that were previously empty of them.

The world that these birds call home is shrinking. Any patch of open grassland with suitable burrows can be, to a burrowing owl, a 'field of dreams'. Save it, and they will come.

© Kelly Stewart

Dept. of Anthropology, University of California, Davis, CA 95616.
e-mail: kjstewart@ucdavis.edu