Resource-diversity relationship in hummingbirds, the underlying mechanism of aggressive resource neglect, and its application to reconciliation in urban habitats

Background/Question/Methods:
Diversity within a habitat is determined largely by ecology and species interactions. Indeed, aggressiveness and interference competition have been studied extensively as a density-dependent mechanism, regulating habitat use and species distribution. When individuals compete for the same resource, interspecific interference can promote coexistence through spatial or temporal habitat partitioning. Studies to date, have rarely examined the effect of intraspecific aggression in promoting coexistence and diversity. This is especially true in urban areas, where the role of community organization and mechanisms of coexistence are poorly understood. This information is important for ecologically oriented, reconciliation of wildlife in human dominated areas.
I studied the resource-diversity relationship in hummingbirds in Tucson, AZ. I also examined the community organization and competitive interactions within and among four species of hummingbirds. Specifically, I answer the questions: What is the effect of artificial resource augmentation on hummingbird diversity?  And what mechanism underlies this pattern? I suggest that intraspecific aggressive resource neglect can promote interspecific coexistence and result in higher hummingbird diversity.
In order to carry out this study, I established the Tucson Hummingbird Project (http://hummingbirds.arizona.edu). This is a citizen science, reconciliation ecology project. Its aim is to study community ecology, monitor and conserve hummingbirds in Tucson, Arizona. Citizen-scientists reported hummingbird abundance and behavior in their backyards. Amount of resources (feeders and nectar plants) varied between yards.

Results/Conclusions:
Hummingbird diversity, rather than merely abundance, increased as the number of feeders increased. Competitive interactions vary between species. Notably, intraspecific competition takes precedence over interspecific competition in the dominant and most common species, Anna’s hummingbird (Calypte anna).
The experimental evidence supports my hypothesis; intraspecific aggressive resource neglect can explain the resource-diversity pattern in hummingbirds. Besides the theoretical aspects, I discuss practical implications of this study. Our knowledge of the community organization, together with our understanding of the ecological mechanism underlying the resource-diversity pattern of hummingbirds in Tucson, AZ, enable us to suggest scientifically based ways to reconcile human habitats with nature. By adding resources according to an ecologically based protocol, we can actively increase biodiversity in human manipulated areas and surround ourselves with native wildlife, such as hummingbirds. For one to be Papageno (Birdman), the magic flute should be replaced by a feeder, enabling to indeed “equally give sugars”.