Lucky ‘Angel Hawk’ Makes a Remarkable Recovery: By JOE EATON

Special to the Planet
Tuesday September 07, 2004

I just finished a collection of natural history essays by Howard Ensign Evans, a retired entomologist in Colorado. One of the pieces, about a meadow where he and his wife had enjoyed songbirds and wildflowers, concludes with this paragraph: 


The meadow is now posted and is becoming a housing development. That, of course, is how essays on environmental subjects usually end. 


He’s right; modern environmental writers are about as cheerful as Richard Thompson. But if doom is our stock in trade, it’s only a reflection of the steady drumbeat of bad news: mass extinction, habitat loss, global warming, West Nile virus, overfishing. Think of all those PBS nature documentaries that end with the sound of the chainsaw. 

But there are times when we have something to celebrate rather than mourn. A couple of weeks ago I spotted a white-tailed kite at the Berkeley Marina, hovering over the field where University Avenue feeds onto Interstate 80. These raptors used to be called “angel hawks”; they’re mostly white, with pale gray wings and black shoulders, and have an ethereal look. The story of the kite is a welcome counter-example—a native species that made it back from the edge of the abyss. 

James Cooper, who published the first major study of our state’s birds in 1870, described the white-tailed kite as “quite abundant in the middle districts of California,” especially in the tule marshes of the Sacramento Valley. That was the case up through the mid-1890s, and then the kite population nosedived. In 1927 Ralph Hoffman, author of the pioneering field guide Birds of the Pacific States, estimated there were “not more than 50 pairs left in California.” 

Five years later Gayle Pickwell described the bird as “probably a dying species.” Joseph Grinnell and Alden Miller confirmed in 1944 that the kite was “rare or entirely gone” from most of its former range. 

What had happened? In part, it seems to be the old familiar story of habitat loss: wetlands drained for farming. Californians shot a lot of kites, too. The birds were unwary and made conspicuous targets. Although kites feed almost exclusively on small rodents, they were believed to prey on quail and ducks as well, and hunters killed them to eliminate the competition. Along with crows, jays, owls, and other hawks, they were targeted in mass hunts sponsored by manufacturers of ammunition. 

Then there were the oologists. Egg-collecting was one of those late-Victorian obsessions (remember Peter Cook’s character in The Wrong Box?) The eggs of the white-tailed kite, considered among the most beautiful of North American birds’, were a particular prize. 

And the increasing scarcity of the kites after the turn of the 20th century only whetted the collectors’ appetites. 

So the kite looked like a goner. But a funny thing happened on the way to extinction. Around the time of the Second World War, birders began to notice an upswing in kite numbers. And the trend continued into the ‘50s, the ‘60s, the ‘70s. White-tailed kites reclaimed much of their lost range in California and pushed north into Oregon, where they had never nested historically. They bounced back in Texas, too, and spread into Central America all the way south to Panama. The kite have had their ups and downs, declining during drought years in the last couple of decades, but they’ve come a long way from Hoffman’s 50 pairs. 

Legal protection, which came in 1905, clearly helped the kite. But this was long before the Endangered Species Act: the white-tailed kite never had a recovery plan, a captive breeding program, a critical habitat designation. In part the bird seems to have been the unintentional beneficiary of man-made changes to the California environment. And it had a set of traits that positioned it for a comeback once the shooting stopped. 

Although conversion to farmland destroyed much of the kite’s original habitat, farmers created something to replace it. Kites eat voles; voles require standing water; and fields that are irrigated year-round are a vole’s paradise. The dependable supply of rodents may have boosted the kites’ breeding success and compensated for natural fluctuations tied to rainfall cycles.  

In a 1971 article in American Birds, Eugene Eisenmann speculated about other factors in the kite’s recovery. Most birds of prey maintain exclusive territories. White-tailed kites, though, are flexible enough to nest in colonies and share hunting grounds when conditions are right. Typical hawks lay two or three eggs and produce only one brood per year; kites have four- or five-egg clutches and are sometimes double-brooded. Rather than occupying the same territory year-round, kites evolved a nomadic lifestyle, going where the voles are. This tendency to wander favored the dispersal of pioneering birds into vacated portions of the species’ range. 

During the white-tailed kite’s rebuilding years, the populations of other raptors—the peregrine falcon, the osprey, the bald eagle—went down the tubes, largely as a result of pesticides like DDT. Eisenmann suggested that the kite may have escaped the worst effects of pesticide contamination by eating low on the food chain. 

Kites eat voles that eat leaves and seeds: two steps from primary producer to predator. Eagles and ospreys, on the other hand, eat big fish that have eaten smaller fish (and so on), accumulating higher levels of toxins in the process. 

Let’s not get too optimistic here: the example of the white-tailed kite doesn’t show that endangered species can make it back from the brink of extinction without human assistance. The kite’s recovery seems to have reflected a unique mix of environmental factors and life-history traits. It was, in short, one lucky bird. And we are lucky as well that we can still see angel hawks from the freeway.m