Time, Energy, and Territoriality of the Anna Hummingbird (Calypte anna).
The male Anna Hummingbird accommodates seasonal changes in energy demands by varying its allocation of time and energy among different activities; total energy expenditures change relatively little. Augmented terrritorial defense during the breeding season is made possible by increased feeding efficiency due to the availability at this time of very nectar-rich flowers.
Stiles
F G
FG