Occupancy, productivity, turnover, and dispersal of Northern Goshawks in portions of the northeastern Great Basin

We determined the occupancy, productivity, turnover, and dispersal distances of Northern Goshawks (Accipiter gentilis) in two areas of the northern Great Basin in northeastern Nevada and southern Idaho from 1992-2003. Occupancy of nesting territories declined in both study areas over the 10-11 yr study period but the decline was statistically significant (P <0.05) only in northeastern Nevada where it decreased from a high of 83% in 1997 to a low of only 23% in 2002. The average productivity of goshawk breeding pairs did not change significantly in either study area, but it was lowest in southern Idaho at only 1.5 ± 0.6 young/breeding pair and highest in northeastern Nevada at 2.3 ± 0.8 young/breeding pair. Males bred mostly at 3yr of age and females bred at 2 yr of age with both sexes residing in nesting territories an average of 2 yr. We found no difference in the number of nesting territories used by either sex with 88% of adults using only one nesting territory, 10% using two nesting territories, and 2% using three nesting territories. Turnover of males and females ranged from 12.5-22.9% and 16.2-30.0%, respectively, and did not differ significantly. Breeding dispersal of males and females ranged from only 2.1-5.8 km but natal dispersal was 19.1 km for males and 96.4 km for females indicating that the female segment of the population was the dispersing sex. Several goshawks captured on migration at the Goshutes Mountains in northeastern Nevada were reencountered as breeding adults in both southern Idaho and northern Nevada suggesting that Northern Goshawks in the northeastern section of the Great Basin constitute a large metapopulation consisting of several subpopulations occupying the isolated mountain ranges of Nevada, Utah, and southern Idaho. With dispersal distances of nearly 100 km, female goshawks are capable of being recruited into breeding populations throughout the northeastern segment of the Great Basin.