Nesting Ecology and Production of Western Grebes at Bear River Migratory Bird Refuge, Utah

Mark L. Lindvall, Jessop B. Low
1982 The Condor  
The nesting ecology of Western Grebes (Aechmophorus occiden-t&is) was studied at Bear River Migratory Bird Refuge, Utah, in 1973 and 1974. Western Grebes nested on dry land, emergent vegetation, and in open-water areas in colonies and single nests. They selected sites near open water (approximately 30 cm in depth). At least one young hatched in 2 1% of the nests. Avian predation and abandonment of nests caused the largest losses. Mated pairs produced an average of 1.7 young. Western Grebe
more » ... Western Grebe nesting habits have been described by several authors. Bent (19 19) characterized nests in North Dakota, California, and Saskatchewan, as floating in emergent vegetation. In Oregon, Finley (1907) found three or four eggs to be the usual clutch size. Palmer (1962) summarized available information on the courtship behavior, range, plumage characteristics, nesting habits, and food habits. Herman et al. (1969) and Rudd and Herman (1972) described the effects of DDT contamination on Western Grebes, and Lindvall and Low (1979, 1980) reported on organochlorine pesticide and PCB residues in these grebes. Because the breeding biology of Western Grebes has received little comprehensive study and may be affected by pesticides, we wished to further investigate reproductive success. In 1973 and 1974 we examined nests and nesting habitat and investigated causes of nest loss at Bear River Migratory Bird Refuge. STUDY AREA AND METHODS Bear River Migratory Bird Refuge is 25 km west of Brigham City, Utah, on the northern edge of the Great Salt Lake. Water from the Bear and Malad rivers is held in five large impoundments at the refuge by a system of dikes and canals. The refuge contains 9,268 ha of open water, and 5,811 ha of marsh. The marsh most nearly fits the class IV (semipermanent ponds or lakes), D (brackish), cover type 4 (open water or bare soil on 95% of the wetland area) according to the classification of Stewart and Kantrud (197 1). Narrowleaf cat-[661 ,/--\
doi:10.2307/1367823 fatcat:cayn2ngbqnbsrdfzjfqpcdjp2a