Economics of Breeding Territoriality in Male Calliope Hummingbirds

Abstract

Abstract Several lines of evidence indicate that the territorial behavior of postbreeding North American hummingbirds can be explained in primarily energetic terms. The territoriality of breeding males, however, may be different in that it may play an important role in courtship. The results of this study on breeding male Calliope Hummingbirds (Stellula calliope) indicated that territoriality could not be explained either directly or indirectly in terms of defense of energy resources. Throughout the 2-month breeding season, flower sampling indicated that males could have obtained energy faster by foraging on nearby undefended areas than by foraging on their territories. In June there were no profitable flowers on the territories, and males did all or nearly all of their foraging away from their territories. In May, when territory nectar availability was fairly high, males did not leave, expand, or shift their territories in response to experimental exclosure of all profitable flowers on those territories. I suggest that males may have preferentially selected territory sites with prominent perches near females' nesting areas, and that these considerations outweighed the potential benefits of defending territories on areas with high-quality nectar resources.