Unusual Predatory Activities of Mexican Jays and Brown-Headed Cowbirds under Conditions of Deep Snow in Southeastern Arizona

Abstract

Snows of any depth and duration are unusual in the Chiricahua Mountains at the elevation of the Southwestern Research Station (5400 ft). Usually the snow covers the surface for only a day or two, after which large patches melt off, allowing ground-feeding winter birds access to foraging areas. On 14 December 1967 an area-wide storm struck southeastern Arizona and southwestern New Mexico. By 17 December 31 inches of snow covered the ground. It remained for a full week before the first patches of earth were exposed. Many local birds were obviously hungry and the Mexican Jays (Aphelocoma ultramarina) became especially aggressive at our feeding stations. During this time one of these jays was seen to swoop down on a small bird and kill it by pecking. The prey appeared to be a sparrow but could not be retrieved because of the deep snow. On the same day two male Brown-headed Cowbirds (Molothrus ater) were seen attacking a junco (Junco sp.) on the snow. A female cowbird standing in the snow about a foot away watched the attack. Both males were pecking at the junco, which was struggling in the snow. The attackers were disturbed by the author and the junco flew off, but fell into the snow about 50 ft away, obviously hurt or weakened. Feathers were strewn about the area of attack. Tufts of feathers, perhaps also of juncos, gave evidence of three other attacks, probably by jays. The evidence is circumstantial but there were no mammal tracks about, or predatory bi ds. The cowbirds were not seen again, but a flock of 13 jays remained in the area through the winter. A. C. Bent (U.S. Natl. Mus., Bull. 191, 1946, and Bull. 211, 1958) does not mention predatory activities by this species of jay or by the Brown-headed Cowbird.