Grays Lake Ecosystem. Comparison of Wetland and Upland Management Practices at Grays Lake National Wildlife Refuge ? Nesting Birds

Authors(s): J. Austin

Publication:

Publisher:

Publication Date: 0000-00-00

Type:

Location:

Abstract: This component of the management study examines nesting activity and success of breeding birds in wet meadow and grassland habitats. Very little nesting data has been collected at Grays Lake for these habitats. Treatments can dramatically alter nesting habitat: idle treatment should yield greater nesting cover for those species that prefer well-concealed nests, whereas grazing and burning treatments should provide short cover attractive to other species such as long-billed curlews. Changes in plant species, which provide both nest-building material and structure for cover, may also change the attractiveness of a unit to a nesting bird. More indirectly, differences in habitat resulting from management treatments may affect movements of predators and the abundance of alternative prey (small mammals). Because low numbers of nesting ducks are anticipated in burned or grazed areas and low numbers of other species of nesting birds are anticipated in idle areas, meaningful comparisons of nest success among treatments may be difficult. Therefore, this effort will primarily address the level of occurrence for each nesting species, phenology of nesting, nest site characteristics, and current rates of nest success. The first nest search of each year focuses on the early-nesting sandhill cranes and Canada geese. These searches are largely visual because these large nesting birds are very visible before vegetative growth starts. We then conduct 3-4 additional nest searches during mid-May-late June for all nesting bird species, covering all of the unit that may provide nesting habitat. During these searches, accessible areas of each unit are searched using a chain-drag using ATVs; areas not accessible by ATV are searched on foot. Nest data are collected using standard protocol developed at Northern Prairie; these include nest site vegetation, water depth, incubation stage, number of eggs, and nest fate (successful, destroyed, abandoned, other). In the first two years of the study, we located and monitored 834 nests of 20 bird species (Canada geese, sandhill crane, American coot, eared grebe, mallard, gadwall, pintail, cinnamon teal, canvasback, American avocet, Wilson phalarope, common snipe, blue-winged teal, green-winged teal, northern shoveler, redhead, ruddy duck, northern harrier, long-billed curlew, and short-eared owl). Nest success for ducks is variable among species, years, and units. Apparent nest success is highest for American coots (83-88%) and avocets (72-79%). Nest success of cranes increased from 43% in 1997 to 65% in 1998, whereas nest success of Canada geese declined from 46% in 1997 to 11.6% in 1998, apparently due to higher predation losses. Most duck nests are located in upland grasses while geese and crane nests are most often located in baltic rush and sedges. In 1999, nesting by most species was noticeably later, following a cool and snowy start. We located 519 nests of 16 species. Numbers of coot nests increased dramatically to 430, reflecting the high numbers observed in the breeding bird surveys. Nest success declined for coots (to 63%), and was 44% for sandhill cranes and 58% for Canada geese. In 2000, we located 372 nests of 13 species. Coot nests still comprised the majority of nests (247 or 66%). Nest success rates for coots, sandhill cranes, and Canada geese were similar to that in 1999. Relatively few duck nests were found in any one year. Preliminary assessments suggest no dramatic effects on nesting due to treatments. Rather we suspect changing predator community and activity patterns and differences due to weather affected nesting birds in 1999 and 2000. At the conclusion of the study, we will assess treatment effects where possible, and describe the nesting bird community, habitat use by species, and general nesting biology for each species.

Keywords: Gray's Lake, Idaho, ecology, breeding, management, animal, bird, nest, nesting, Aves, ornithology, population, mortality, fire, grazing, curlew, long-billed curlew, Numenius americanus, predation, mammal, rodent, duck, waterfowl, water bird, Anatidae, crane, sandhill crane, Grus canadensis, goose, Canada goose, Branta canadensis, American coot, Fulica americana, coot, grebe, eared grebe, Podiceps nigricollis, mallard, Anas platyrhynchos, gadwall, Anas strepera, pintail, Anas acuta, canvasback, Aythya valisineria, cinnamon teal, Anas cyanoptera, avocet, American avocet, Recurvirostra americana, Wilson's phalarope, Phalaropus tricolor, snipe, common snipe, Gallinago gallinago, blue-winged teal, Anas discors, teal, green-winged teal, Anas discors, northern shoveler, Anas clypeata, redhead, Aytha americana, ruddy duck, Oxyura jamaicensis, northern harrier, Circus cyaneus, short-eared owl, Asio flammeus, raptor, owl, waterfowl, water bird