Black and turkey vulture roost dynamics, marking, morphology and nesting in Virginia

Abstract

Black vulture (Coragyps atratus) and turkey vulture (Cathartes aura) roosting dynamics were studied at eight roosts near Radford, Virginia. Black vulture numbers at a permanent roost ranged from low monthly means in June 1982 and 1983 to peak monthly means in December 1981 and 1982. Turkey vulture numbers ranged from low monthly means in July 1982 and 1983 to peaks in December 1981 and 1983. Vultures used two temporary roosts at nearby landfills from March through October in 1983. Vultures marked with cattle eartags were observed moving among roosts. Road counts were poorly correlated (r = 0.39, P = 0.05, r = 0.39, P = 0.12, black vultures and turkey vultures respectively) with roosting vulture numbers, and may not be good indicators of vulture numbers. Long term monitoring of vulture populations is best accomplished by six counts in December, on the same date each year, as vultures leave permanent roosts. Movement of problem roosts may be most effective when accompanied by removal of attractants. Accretion of fecal material on metal leg bands constricted tarsi of black and turkey vultures. Teflon bands did not constrict the tarsus, but tag loss was high. Adult black vultures had longer tarsi and shorter wing chords than juveniles. Two nests were used in 1983 and 1984 by two pairs of black vultures, consisting of one marked and one unmarked bird.