Data from: Causes of differential migration distance: Test of seven mechanistic hypotheses in an arctic raptor

Exploring the causes of differential migration, or variation in migration
distance, has increased our understanding of the remarkable variation in
migratory behavior exhibited by birds more generally. However,
considerable uncertainty exists regarding the mechanisms underlying
differential migration distance in birds, despite it being a common
phenomenon. We leveraged migration distances from GPS-tracked rough-legged
hawk, Buteo lagopus, to test predictions deduced from seven
hypotheses proposed to explain the underlying cause(s) of differential
migration distance. We provide the first empirical evidence in support of
a social dominance food maximization hypothesis whereby dominant
individuals migrate to higher quality nonbreeding locations with respect
to foraging efficiency regardless of migration distance. Within females,
larger, more dominant individuals migrated intermediate distances while
smaller, subordinate individuals migrated both longer and shorter
distances. We also found support for the social dominance distance
minimization hypothesis because more aggressive females migrated shorter
distances, although increased aggression at shorter distances may be a
consequence of poor body condition. Within males, we found some support
for the fasting endurance and thermal tolerance hypotheses because body
size was negatively correlated with migration distance. Body size was also
negatively correlated with food availability and winter minimum
temperatures within both sexes, providing additional mechanistic support
for the fasting endurance and thermal tolerance hypotheses. Overall, our
results suggest that differential migration distance within rough-legged
hawks is caused by a combination of competition for nonbreeding resources
and constraints on fasting endurance or thermal tolerance, but is
unrelated to competition for breeding opportunities, dietary preferences,
or flight efficiency.