| Summary: | Thesis (M.S.)--Humboldt State University, 1980 A study to determine the migration and wintering ground distribution, ecology, and population status of the endangered Aleutian Canada goose (Branta canadensis leucopareia) was conducted from October 1975 to May 1978. Field investigations extended from the western Aleutian Islands, Alaska, to the. Central Valley of California. Prior to and during the study, 536 Aleutian geese were banded to document movement and survival. It was determined that the geese use traditional migration and wintering areas away from Alaska, returning to virtually the same fields annually. During September, Aleutian Canada geese migrate along the Aleutian Island chain from Buldir Island near the western end to the easternmost island of Unimak and then apparently shift southeast on a transoceanic flight. The geese arrive in California in early October; some stop near Crescent City, but most birds continue to the Sacramento Valley where over 95 percent of the population uses a small agricultural area in the Butte Sink. From mid-November to early December the geese move southward via the Sacramento-San Joaquin River Delta to the grasslands of the upper San Joaquin Valley. Most of the birds are present as a single flock near Modesto from at least late December to early February. They begin shifting southward to an area near Los Banos in mid-January, and some are present until mid-March. Aleutian geese start moving northward to the Crescent City staging grounds as early as mid-January, with most of the birds arriving during March. They peak in number there in late March and early April when nearly the entire known iv population is present. In mid-April, geese begin to leave Crescent City to the breeding grounds, and by late April or early May all have left. Although a few Aleutian Canada geese have been reported near the mouth of the Columbia River, Washington, most apparently make a transoceanic flight to the eastern Aleutians. There, they continue westward to Buldir where they have been seen as early as the first week of May. During the study, hunting and avian cholera were found to be the main sources of winter mortality. Closure on Canada goose hunting enacted in three areas of California at the onset of the study has reduced mortality from an estimated preclosure rate of 22.5 percent annually to approximately 11.5 percent during winters 1975-76 and 1976-77. This winter mortality may comprise the majority of the annual loss. The spring population increased 45.6 percent, from 790 in April 1975 to 1150 in March 1977. Management needs on the migration and wintering grounds include continuation of protection of the geese through hunting closures and maintenance of suitable habitat conditions on their major use areas.
|
|---|