TERRITORY REGULATION, TENURE, AND MIGRATION IN RUFOUS HUMMINGBIRDS

Postbreeding migrant rufous hummingbirds (Selasphorus rufus) establish feeding territories in alpine meadows. An inverse hyperbolic relationship between territory size and flower density indicates that territory size is regulated to maintain food supply: individual hummingbirds make daily adjustments in their territories. These adjustments maintain food supplies from day lo day and improve them over what they would be if no adjustments were made. The ability of individuals to maintain territory quality, however, and the length of time they remain in the meadows, is affected by their age and sex and by the level of competition for food by conspecifics. Territoriality, therefore, must be considered in relation to factors operating beyond the local food environment, both in terms of effects on and effects of the short-term dynamics of energy regulation. This has important implications for hummingbird migration. © 2015, National Research Council of Canada.