Audubon July 1977 [antikvár]

Keeping track of hawfcs by DAVID R. ZIMMERMAN I GET A CHARGE from going out to hear red-shouldered hawks calling over their territories and to watch them display," says 27-year-old J. Edward Hanna. He is a quiet-spoken Canadian who works in downtown Toronto analyzing aerial photographs for oil companies and other developers. Now he is groping for words to describe why, at 5:30 of a clear but remarkably chilly May morning, he is perambulating a boggy woodlot near Toronto's still-rural northern city limit where red-shouldered hawks continue to reside. Ed Hanna also is trying to explain the persistence with which he pursues his research on the red-shouldered hawk, for which he has neither academic nor governmental sanction or support, and which he hesitates to publish for fear his pro-conservation bias will offend his boss. On a rare visit lo the nest, a r, incubation duties while his m seldom build Iheir own nesis, occupied a bulky old magpie spruce. Not much bigger thar on a wide variety of songbird.' warblen Insects,, much bl oflleke tdragonflle ndeven on bats. Merlins ¦ger birds tike gulls and c tale merlin briefly assui lie feeds nearby Metili and this pair in Alaska test thirty feel high mc a thrush, the merlin pr ,from attd other large ilso like lo badger ¦ows. (Noel Snyder) In his avocational effort, Hanna is one of a growing corps of biologists, conservationists, falconers, and birdwatchers who are trying to learn enough about North America's rich populations of hawks to prevent a repetitionof the peregrine falcon's tragic decline and fall. A fellow Canadian, Richard Fyfe, who is among the world's foremost raptor biologists, expresses this common concern when he says; "1 just don't want to be caught again like we were with the peregrine, starting after the fact, when it's too late." Hawks are a particular cause for concern because they feed on other birds and on mammals, thereby concentrating in their own bodies DDT and other environmental poisons that are present in their prey. Hawks are large birds that are easily shot and trapped, and their former poor reputation as "varmints" has not been wholly eclipsed by the more environmentally sound judgment that they, like other predatory animals, are beneiicial-as well as beautiful-balancers of nature. The word hawk, which is not a scientific term, is used to describe day-hunting predatory birds equipped with curved claws and beaks; they are smaller than their close relatives, the eagles. Keeping track of North America's hawks is an awesome task. Twenty-one species breed on this continent north of the Mexican border, of which fifteen are widely distributed. Of the fifteen, six are buteos, broad-winged soaring birds. There are five long-winged falcons, of the genus Faico, and three short-winged hawks, of the genus ^cc/^/rcr. The harrier, or marsh hawk, is the sole exemplar of its genus in North America. In order to foretell and, it is hoped, forestall fresh tragedies, biologists want basic, undramatic, but difficult-to-collect data on each of these species. They want to know: Is the population declining? If so, is the decline temporary and self-correcting? To answer these questions, the scientists would like to know the normal, pre-stress popuiation-the baseline data. They also want to know a species' population dynamics: how many young birds must be fledged each summer to replace losses and maintain numerical stability Since natural conditions and human hazards vary sharply from region to region, there is need to know these answers for each species in several or more places. The task thus requires a far larger and more eff'ective army of workers than the corps of enthusiasts, including Ed Hanna, who already are in the field. His bird, the red-shouldered hawk, reportedly is doing well in California, for example. But it is in trouble in the much larger, eastern part of its breeding range, and at the northern limit-in the Toronto area between Lake Huron and Lake Ontario-its future is very much in doubt. To find and monitor the roughly one dozen nests that remain active each year in an area of about 250 square miles is difficult work. It demands both of Hanna's annual vacation weeks and virtually all weekends from mid-March, when the stick nests that remain from previous years can be seen in the crotches of still-barren hardwoods, until mid-June, when the young hawks fledge. In recent years, Hanna has tramped 300 woodlots looking for nests. One technologically sophisticated tool has proved helpful: Hanna finds he can use aerial survey photos to locate suitable red-shouldered hawk breeding terrain-wooded floodpiains or side slopes alongside a river or pond. He has found that active nests are, on the average, 42 feet from water. The last time raptor populations were censused around Toronto, two decades ago, there were 60 active red-shouldered hawk nests in an area only half as large as that in which Hanna in most years has found fewer than a dozen active nests; last year, a banner year, he found 24. Conveniently for him, but boding still more trouble for the hawks, many of the remaining nests are concentrated along the city's edge, in the path of developers' bulldozers. On his early morning tour of the area, Hanna pointed to a recently cleared site on which Toronto's new zoo has been built. "The monorail went right through the woods the red-shouldereds were in," he said. "They cut down the nest tree. During construction, the birds tried to build nearby in a beech tree. But it was a bad site; the nest was not successful." The next nest site on his route, near a railroad, was reached by a woodsy path carpeted with violets, trilliums, and little piles of soggy garbage. Hanna "read" the songbird sounds in the woods with zest and skill: "There's a parula warbler. Lots of Nashvilles. The trees are loaded with warblers!" The hawk nest was stuffed into a fork halfway up the tallest of a lot of scrubby oak trees that Hanna said were suboptimal breeding habitat. The nest looked deserted, although Hanna had seen the female sitting on it only ten days before. "That's disturbing," he exclaimed, inspecting the nest through binoculars. "It's beginning to fall apart. I don't see hide nor hair of her. Nests usually are generously decorated with fresh hemlock sprigs. And there is a lot of feather down around the nest just before hatching." Neither vital sign could be seen. "1 didn't expect that," Hanna said disconsolately. "She raised young last year" Then, as he walked away, a single shrill cry came up from the tree. Hanna turned in time to glimpse a big reddish-brown bird flash into view by the nest, then vanish. The nest was not abandoned. Hanna was heartened, though not wholly-there still were too many bad signs. "No fluff around," he repeated.