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In 1935 a fledgling female, unmistakably a cahow, struck St. David's Light, close to Cooper's Island, and was obtained by William Beebe, who was then living on Nonsuch Island, where he had organized his bathysphere descent, but again no thorough search was made. The next specimen was collected in 1945 by Fred T. Hall, who found a badly mauled bird washed ashore on Cooper's Island. Finally, in 1951, an expedition headed by Robert Cushman Murphy and including the 16-year-old Wingate discovered several nesting sites, one of which was occupied. "With a noose at the end of a pole we presently succeeded in hauling out the bird," Murphy wrote. "It was the hoped-for but only half-anticipated cahow.... Our exciting captive bit the hands that grasped it, but only briefly and halfheartedly. Within a moment it became completely nonresistant, allowing itself to be stroked, tickled and passed from hand to hand."
Murphy's expedition located seven nesting pairs on two islets. Since searches of the larger and more accessible islets turned up only mingled rat and cahow bones, Murphy believed that rats were limiting the cahow population. For this reason, the first step toward protecting the bird was to eliminate the rats by trapping and poisoning them. (This didn't endanger the cahows, as seabirds never feed on land.) However, it soon became obvious that the rats had had little effect. Improbably, the real villain was the white-tailed tropic bird, or longtail, as it is called in Bermuda, a handsome seabird a little larger than a cahow, which nests there in substantial numbers.
The diurnal longtail returning to breed in mid-March, shortly after the cahow chicks hatched, entered the cahow burrows while the adults were feeding at sea and kicked and worried the helpless chicks to death. Thus, in 1951, all four known cahow chicks were killed, their corpses found in a litter of bones representing generations of baby chicks. It appeared, therefore, that the only reason the cahow had survived at all was that it was nocturnal and the longtail diurnal, so they rarely met. By the time a pair of longtails was staying overnight to incubate their egg, the cahows, having lost their chick, would have abandoned the burrow. Because cahows are longer-lived than longtails, they had a slight chance of rearing a chick if, for some reason, a pair of longtails didn't occupy the nest in any one year.
Although this might explain how the cahow survived the last 300-odd years, it doesn't account for its former abundance. The reason is that in prehistoric times the cahow and the longtail bred in separate ecological niches, the cahow inland where it could tunnel into soily hillsides, the longtail in natural holes and crevices in rocky coastal cliffs. Although overlap occurred and thousands of cahow chicks perished in the marginal zones, the slaughter had a negligible effect on the total population. However, by the time Bermuda was colonized the hogs had eliminated the cahows from their natural habitat, and they were confined to the offshore islands. Since virtually every island with soil cover has been inhabited by man at one time or another in Bermuda's history, the cahow's breeding grounds have been reduced to the smallest and the least accessible and desirable islets where there is insufficient soil for burrowing and where the cahow has come more and more into competition with the longtail. Man has long since abandoned many of the preferable islands, but the cahow is semicolonial, has a strong homing instinct and stubbornly persists in returning to the handful of rocky islets.
When the longtail's role was understood, it was proposed that all the longtails which frequented the two islets should be shot, and a number of them were. But it soon became apparent that the massacre of hundreds of long-tails for the sake of a rather drab bird which was never seen was unjustifiable. So from 1952 to 1955 three naturalists attempted to scare off any longtails which sought to enter cahow nests. This proved impracticable and the cahow chicks continued to be killed.
In 1954 Richard Thorsell, a graduate student, came up with an ingenious solution—a baffler. Taking advantage of the fact that the longtail is slightly larger than the cahow, Thorsell placed an artificial wooden or stone entranceway before each cahow burrow, just big enough for a cahow to squeeze through but too small for a longtail.
The baffler notwithstanding, the cahow population remained static until Wingate took over the program upon graduation from Cornell in 1957. It was soon obvious to him that the bafflers weren't working properly. The difference in size between the cahow and the longtail is minute and the bafflers hadn't been made to precisely the right dimensions. In the spring of 1958 Wingate spent six weeks living in a hut on one of the islets, sleeping days and working nights, gradually reducing the size of the holes in order to condition the cahows to enter ones which they had previously balked at.
A further problem now arose: at times, no matter how small Wingate made the entranceway, a longtail would push itself through. Providentially, he soon discovered that the longtails which could not be dissuaded were those which had previously nested in that particular site; these Wingate has had to kill. Whenever a cahow pair nests in a burrow he knows to have been previously inhabited by longtails, Wingate goes out at dawn two weeks before the longtails are due back and plugs up the burrow, returning at sunset to unplug it. He follows this procedure until the presence of footprints in the sand outside the burrow tells him that the longtails have returned. The following morning he places the plug partway down the tunnel, waits a number of yards off, and when a longtail enters, reaches in, grabs it and drowns it. He has to repeat this procedure the following morning because if he doesn't kill both birds, the survivor will remate and the new pair will attempt to enter the burrow. As a result, from 1961 on no cahow chicks have succumbed to longtails.
In the long run, however, bafflers are impractical, principally because they have to be checked daily throughout the breeding season: a twig or pebble lodged in the entrance by a cahow can forestall entry. (One of Wingate's recurring dreams is that cahows are nesting in a building on Nonsuch, but all the doors and windows are shut so the adults can't get in to feed the chicks.) But at times high seas make it impossible to land on (or leave) the cahow islets, which have no harbors. Wingate was once marooned without food for three days when a storm arose.
Because chick mortality had been virtually 100% in the seven known nest sites up to 1958, Wingate suspected that there had to be a number of undiscovered burrows not subject to longtail competition; otherwise the cahow simply couldn't have survived. By 1960 he had found 11 more nests on three additional islets. (The reason they remained undiscovered was that the cahow's habits were not fully known; starting about December 1st the birds leave the breeding grounds for six weeks, returning only at the moment the females are ready to lay, and the early searches had been made during this exodus period.) Fortunately, the rocks on these islets are so riddled that the cahows, who seek their nests on foot, were able to find holes that longtails, which search entirely on the wing, had overlooked. Even so, four of the newly found nests were subject to entry by longtails.