Nesting ecology of waterbirds at Grays Lake, Idaho

Montane wetlands provide valuable habitat for nesting waterfowl and other waterbirds in the western United States, but relatively little information is available about the nesting ecology of their waterbird communities. We describe the general nesting ecology of breeding waterbirds at a large, shallow, montane wetland in southeastern Idaho during 1997-2000. Habitats include upland grasslands and intermittently to semipermanently flooded wetland habitats. We located a total of 1207 nests of 23 bird species: Eared Grebe ( Podiceps nigricollis ), Canada Goose ( Branta canadensis ), Mallard ( Anas platyrhynchos ), Gadwall ( A. strepera ), American Wigeon ( A. americana ), Green-winged Teal ( A. crecca ), Blue-winged Teal ( A. discors ), Cinnamon Teal ( A. cyanoptera ), Northern Shoveler ( A. clypeata ), Northern Pintail ( A. acuta ), Redhead ( Aythya americana ), Canvasback ( A. valisineria ), Lesser Scaup ( A. affinis ), Ruddy Duck ( Oxyura jamaicensis ), Northern Harrier ( Circus cyaneus ), American Coot ( Fulica americana ), Virginia Rail ( Rallus limicola ), Greater Sandhill Crane ( Grus canadensis tabida ), American Avocet ( Recurvirostra americana ), Long-billed Curlew ( Numenius americanus ), Wilson's Snipe ( Gallinago delicata ), Wilson's Phalarope ( Phalaropus tricolor ), and Short-eared Owl ( Asio flammeus ). Most nests were initiated in May-early June and were terminated (hatched or destroyed) by the 3rd week of June. Mean daily survival rate (DSR) for Canada Goose nests was 0.954 ± 0.005 ( s ￣x ; n = 127 nests), equivalent to Mayfield nest success of 21%. Mean DSR for dabbling duck nests over all 4 years was 0.938 ± 0.006 ( n = 41), equivalent to Mayfield nest success of 11%. For all other species where we found > 10 nests each year (Eared Grebe, Redhead, Canvasback, Coot, Sandhill Crane, American Avocet, and Wilson's Snipe), > 50% of nests found hatched at least 1 young. Success rates for geese, cranes, and ducks were lower than reported for Grays Lake during 1949-1951 and lower than most other wetlands in the region.