This research monitored the condition of migrating sharp-shinned hawks (Accipiter striatus) at a HawkWatch International study site in the Goshute Mountains, Nevada, during the autumn migration seasons of 1994, 1995, and 1996. The HawkWatch research team collected data on nine morphological characters of each sharp-shinned hawk trapped during fall migration; data was obtained from 1,095 individuals in 1994, from 990 individuals in 1995, and from 1,010 individuals in 1996. Using this morphological data, I calculated four different body condition indices that were either used in or suggested by previous studies. The value of all four indices increased as the migration season progressed each year; that is, birds which migrate late in the season are heavier relative to various skeletal features than are those that migrate early in the fall. These findings may be explained by both the “leapfrog migration” and “social dominance” hypotheses of migration. Further study will be required before it can be determined whether either hypothesis is a better descriptor of the migration of sharp-shinned hawks in this region.
Brian Wiebler, ’97
Sponsor: Robert Black