Habitat selection theory predicts that consumers should distribute themselves across alternative resources in a fitnessmaximizing manner. One such distribution is the ideal free distribution, where consumer density matches local resource density. Alternatively, if wing wear is an important cost of wing use for bees, there should be relatively more bee consumers in high density patches, resulting in “overmatching”. If the energetic costs of flight influence patch choice, there also should be relatively more consumers in high density patches (where flight costs are lower), resulting in “overmatching”. To examine these hypotheses, I observed the visitation of bumble bees (genus Bombus) across experimental manipulations of plant density in patches of bergamot (Monarda fistulosa) in southwest Alberta, Canada over 2 summers. Bees flew more often and for a greater proportion of time, and hit their wings more frequently, in low-density patches. In 2004, bees “undermatched” resources (relatively few bees in high density patches). In 2005, bees achieved an ideal free distribution. Overall, wing wear and energy costs alone cannot explain bumble bee use of their floral resources (in either year), while the ideal free distribution sometimes can (i.e., in 2005). This study therefore complements the findings of ideal free distributions in other aspects of the foraging ecology of pollinators.
Nomenclature: Moss & Packer, 1983; Natural History Museum, 2009.