Food of the Peregrine Falcon, Falco peregrinus, in Interior Alaska

Abstract

Medina County, Texas (Edwards Plateau). Some 13 trips have been made there, and flights cheeked carefully. Other observers at Texas bat caves, whether interested in the bats themselves, or the caves which harbor them, have commented on the predation on these mammals by certain birds of prey Several of them mention the Duck Hawk. However, as far as the writer has been able to find, none refers to the habit of this superb falcon of occasionally feeding on the wing. While many instances of predation were noted in 1949, such habit was not observed by the writer until 1950. The method of securing prey varies. At times, the falcon will dive headlong into the stream of bats in a spectacular stoop; again it may fly straight through the "living river," and emerge with a bat in the talons. Also, at times, it flies parallel to them, then swerves sideways, makes a "zoom" and reaches outward and forward with the talons, so seizing a bat. One was seen in early August to miss such a strike then, almost instantaneously, reach sideways with the right foot, and seize a bat. In at least half a dozen instances during 1950, the falcon was seen to begin feeding on the bat at once. Reaching the foot forward and the head downward and back, it devoured the edible portions quickly, releasing the wings which fluttered downward. During this manoeuver the falcon's wings were at right angles to the body, and the bird was soaring. It was exactly the technique of the Swallow-tailed Kite, Elanoides forficatus, in aerial feeding. 1948). The bat preyed upon is the Mexican Free-tailed Bat, Tadarida mexicana. The population of Ney Cave has been estimated at between 20 and 30 million bats. It seems rather obvious that raptorial predation on these animals at this locality is inconsequential, though regular. The writer has never witnessed aerial feeding of the Duck Hawk previously, though he has seen it make many kills.-A•.•xx•D•R SPR•J•, JR., National Audubon Society, Charleston 50, S.C. Food of the Peregrine Falcon, Fatco I•eregrinu$, in Interior Alaska.-On September 24, 1950, a Peregrine's aerie was discovered on some bluffs overhanging the Tanana River near the old town site of Chena, Alaska. A single, adult falcon, probably a male to judge by its small size, was seen to fly down the river and perch on one of the bluffs. Another trip was made to this site on September 30, and on subsequent days, but the Peregrine was not seen again, and it was assumed that the bird had migrated. Investigation of the bluffs revealed a number of feeding shelves and scrapes that were well-covered with droppings, pellets, and the remains of prey. This seemed to indicate that a family of Peregrines had occupied the bluffs during the past summer, and in as much as the Indians living along the river are acquainted with a pair of Peregrines that has nested in past years on some bluffs about five miles farther down the river, this seems even more likely. The remains lying about the bluffs were collected on October I, and the data from these are presented in the accompanying table. Unfortunately it is not known how many Peregrines occupied the bluffs during the breeding season or how long the material had been accumulating below the aerie. The data do, however, give some interesting information on the relative use of various birds as food by the Peregrine Falcon.