| Title: |
Seasonal and annual survival of adult Pacific brant |
| Author(s): |
Ward, D. H., E. A. Rexstad, J. S. Sedinger, M. S. Lindberg, and N. K. Dawe |
| Citation: |
J. Wildl. Manage. 61:773-781 |
| Year: |
1997 |
| Abstract: |
Declining mid-winter counts of Pacific brant (Branta bernicla
nigricans) and reduced numbers of nesting birds on their main breeding grounds
prompted us to assess factors that may be limiting recovery of this population.
We estimated seasonal and annual survival rates of adult brant in 1986-93 from
resightings of leg-banded birds. Brant were banded at a major colony on the
Yukon-Kuskokwim Delta, Alaska (Y-K Delta) in 1986-92, and resighted there in
1987-93 as well as at major fall and spring migration and wintering areas in
1990-93. Seasonal survival was the same for males and females. Mean monthly
survival rate was lowest (P_0.05) in late spring migration (15 Apr-1 Jun), the
period of greatest subsistence harvest on the breeding grounds, and highest in
winter (1 Jan-1 Mar), the period of greatest sport harvest. Annual survival
rate did not vary among years (F=0.51; 5, 718 df; P=0.91) and averaged 0.840
(SE=0.031) from 1986 to 1993. Subsistence harvest has contributed to low
population levels of Pacific brant. |
|
