Empirical support for a despotic distribution in a California spotted owl population

Abstract

Territorial species, such as the spotted owl (Strix occidentalis), are predicted to follow an ideal despotic distribution. However, debate exists on whether wild populations actually meet the assumptions of an ideal distribution, such as perfect perceptual abilities (i.e., the ability to recognize high- and low-quality sites without error). Because this hypothesis has important life history ramifications for spotted owls, we investigated whether occupancy rates of California spotted owl (S. o. occidentalis) territories in the San Bernardino Mountains of southern California positively correlated with a qualitative "potential fitness" (denoted by λpf) estimated from survival and reproduction of territorial owls. Spotted owls in our study tended to occupy territories with the highest λpf, supporting the assumption of ideal perceptual abilities within this population. However, this relationship was noisy, and we suggest that some individuals do not assess site quality accurately because of perceptual limitations, prey dynamics, and large territory sizes. Furthermore, dispersal processes, high survival rates, and long life spans of spotted owls may be other key factors preventing some individuals from selecting sites of the highest quality and, consequently, our ability to precisely estimate λpf.