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Wild Neighbors: Birds in Berkeley: The Owls in the Oak

By Joe Eaton
Tuesday October 30, 2007

Eighty-one years ago Joseph Grinnell, director of UC’s Museum of Vertebrate Zoology, sat in his corner office at the edge of Faculty Glade watching a crew of arborists at work on a venerable coast live oak. Or, as he put it in his essay “Tree Surgery and the Birds,” “ ‘tree surgeons’ … under directions of a ‘landscape architect.’ ” His contempt is evident. Over the years, Grinnell had observed 46 species of birds in that oak. And he noted the removal of bits of the tree that had attracted particular species of birds: the decaying stub where the downy woodpecker drummed, the white-breasted nuthatch’s favorite foraging ground, the flycatcher’s perch. 

“My corner tree used to have knotholes,” he wrote. “One such cavity, years ago, furnished the home site for a Screech Owl, and from it each summer issued a brood of young owls … Nowadays, it seems, the tenets of tree surgery require that no such cavities be permitted to remain in any well-cared-for tree. Each and every former and even potential knothole has been gouged out and sealed up, so that only a forbidding wall of cement meets the eye and beak of any prospecting bird.” 

To Grinnell, the loss of the campus screech-owls was just part of the “local disappearance of our native bird-life.” And he was in a position to know. Hired to run the Museum of Vertebrate Zoology (MVZ) by the remarkable naturalist-philanthropist Annie Alexander (see Barbara Stein’s biography On Her Own Terms: Annie Montague Alexander and the Rise of Science in the American West for more on that working relationship), Grinnell was the architect of Berkeley’s preeminence in mammalogy and ornithology.  

He had been born in Indian Territory where his physician father practiced, and grew up among Red Cloud’s Oglala Sioux. His road to Berkeley led through Pasadena and Alaska. Three years after taking over the museum, he organized an epic Sierran transect that provides a baseline for contemporary studies of faunal response to climate change. During that project, Grinnell once set out from Yosemite Valley and hiked more than 40 miles over the crest to Mono Lake in a single day, shotgun and notebook in hand. 

Grinnell also pioneered some of the fundamental concepts of ecology: ecological niches, competitive exclusion. He recognized that animals shaped their environments as well as being shaped by them, and that variation was the raw material of evolution. 

The year after the attack of the “tree surgeons,” Grinnell and Margaret Wythe published their Directory to the Bird-life of the San Francisco Bay Region, under the auspices of the Cooper Ornithological Club. (His choice of a female collaborator is interesting. Grinnell respected his patron Alexander, but didn’t allow women on MVZ field trips.)  

Grinnell and Wythe documented 159 nesting species in the Bay Area but were pessimistic about their future, expecting that diversity to decline. “Species of birds are disappearing, some never to return,” they wrote; “some species are just about holding their own … On the whole, it looks as though the total number of species in the Bay region at the present time were undergoing decided reduction, due in major part to the elimination of habitats of wide diversity or of productive kinds.” 

Fortunately, their crystal ball was a bit cloudy. William Bousman recently compared the Directory with data from the subsequent 80 years of breeding bird surveys and atlas projects, and found nesting records for 215 species. Many of those were one-off attempts by vagrants; however, 19 species not present in 1927 appear to be here to stay. Some newcomers were commercially exploited species rebounding after the ravages of the plume trade. Others found new man-made habitats like salt ponds and reservoirs, or responded to the regrowth of redwood forests and the planting of urban trees. Range expansions include northern birds moving south, southern birds moving north, eastern birds moving west. 

And what goes for the overall Bay Area goes for Berkeley. Crows and ravens have taken advantage of the garbage we generate. Cooper’s hawks have moved into Berkeley’s street trees. Chestnut-backed chickadees, unknown in the East Bay in Grinnell’s time, feel at home among planted evergreens. Other birds have benefitted from an expanded urban oak population. John Westlake, a long-time Berkeley birder, has a theory that the maturing of all the oaks planted in the early 70s has a lot to do with the current abundance of oak-associated birds like the Nuttall’s woodpecker and oak titmouse.  

“The unhappy future projected by Grinnell and Wythe has not come to pass,” writes Bousman, “at least not yet.” True, there have been tradeoffs.  

If Charles Keeler revisited his old Berkeley haunts, he would miss the yellow warblers and western meadowlarks, as Grinnell would miss the screech-owls. But who could complain about the chickadees? 


Photograph by Ron Sullivan. 

Knothole with a view: western screech-owl in Briones Regional Park.