Briggs, Amy (2010)
The Effects of Social Dynamics and Resources on the Distribution of Western Scrub-Jays.
Bachelor of Arts, Pomona College, Biology.
Advisor: Rachel Levin.
The distribution of any organism is determined by a variety of factors, including resources, geography, climate, and other individuals. In territorial species, the distribution of individuals is largely influenced by the presence of conspecifics. Territorial individuals must choose which spaces to defend, and often base this decision on the presence and density of certain resources such as food. I tested the hypothesis that the Western Scrub-Jay, a year round territorial species, defends food based territories. I predicted that territories would be correlated with oak trees, a major food source, and that the addition of feeders would change territory boundaries. I also predicted that jays would defend food resources from other paired jays but not from floaters. I found that scrub-jays do not have a tendency to locate their territories in areas of high oak density, or with oak trees at all. However, the study site has a relative abundance of oaks which jays may leave their territories to visit and gather acorns. I found that scrub-jays were willing to venture off their territories to visit feeders, and that paired territorial jays defended these feeders from their neighbors. The addition of feeders caused territories to overlap less, possibly indicating an increase in territory defense and vigilance. Scrub-jays called more at feeders placed in the core of their territory than at those on the periphery. These results indicate that scrub-jay territories are at least somewhat food based.