Date of this Version
PROC. NORTH AM. CRANE WORKSHOP 7:258
Because of a 21 % decline in breeding pairs of greater sandhill cranes (Grus canadensis tabida) on Malheur National Wildlife Refuge from 1971 to 1985, a predator control program was initiated in 1986 to enhance production. The primary cause for the decline was low recruitment of young due to high predation by ravens (Corvus corax). raccoons (Procyon lotor), and coyotes (Canis latrans), On average, predators destroyed 46% of all crane nests and 90% of the prefledged colts. Mink (Mustela vison) were added to the program in 1993 after a study showed them to be an important predator of colts. During the 8 years of the predator control program, crane nest success averaged 68%, compared to 47% before the control program. Predators destroyed an average of21.5% of crane nests during the control program, compared to 46% during years when no predator control was practiced. Average colt survival was 15.1 % during the predator control years vs, 9.8 % during years without predator control, and average productivity was 15.9 young per 100 pairs vs. 11.0. The best validation of success of the program was the recovery of the breeding population, which increased from 168 breeding pairs in 1989 to 238 in 1994.