Summary

Description

The nesting population of greater sandhill cranes on Malheur National Wildlife Refuge, Oregon has declined from 236 pairs in 1971 to 181 pairs in 1986. Nesting studies conducted from 1966 to 1936 have repeatedly demonstrated that the primary limiting factor for cranes nesting on Malheur Refuge is the predation of eggs by ravens, raccoons and coyotes, and the predation of prefledged chicks by coyotes. On 21 January 1986, Malheur Refuge staff assisted by U.S. Department of Agriculture Animal and Plant Health Inspection Service employees began controlling predators on approximately 27.000 acres 14 of Malheur Refuge. Control efforts ceased on 18 August, the end of the crane fledging period. One hundred sixtysix coyotes were removed by the following methods: aerial gunning 51, trapping and snares 27, calling and shooting 19, and denning 3. An estimated 44 ravens were removed, using 44 dozen chicken eggs injected with DRC1339. Eleven raccoons were removed, 10 by hunting with dogs and one was caught in a snare. Overall crane production was 50 chicks, the highest count since 1970. Recruitment of crane chicks in the predator control area was 14.9, the highest ever recorded on the refuge. In the nonpredator control area, the recruitment rate was 54 below the 16year average of 6.4. The 1986 nesting data compared to prior years Studies, strongly suggests that approximately 1718 additional crane chicks reached flight stage that would not have survived without predator control. Additional nesting studies of Canada geese and ducks also showed major increases in nesting success in the predator control areas. The objectives of the 1986 effort was to have a nesting success 75, fledging success 25 and recruitment 15 in the predator control area. the actual outcome was 70, 29.9 and 14.9 respectively. Based on these results of the 1986 predator control effort was judged a success. It is recommended that control efforts for1987 be expanded to include all the key crane nesting areas on the refuge 85,000 acres as outlined in the 25 November Environmental Assessment entitled: Alternatives to Enhance the Production of Greater Sandhill Cranes on Malheur National Wildlife Refuge, Oregon.