The spotted owl is one of the most-studied and best-known owls in the world. This degree of scientific attention is the result of this owl's association with late seral stage conifer forests of high commercial value. The bird's ecology and conservation are the topic of vigorous debate among foresters, wildlife ecologists, academics, politicians, social scientists, and economists.

This project is a continuation of a long-term mark-recapture study of northern spotted owls in northwestern California, which began in 1985. This study is the longest running population and demography study on spotted owls in the country. The objectives of this study are to estimate age-specific demographic parameters, understand factors affecting those parameters, and explain mechanisms responsible for variation in population dynamics of northern spotted owls in northwestern California.

We check for reproduction and the presence of mates by feeding up to 8 live mice to individuals located during surveys. Reproductive owls will usually bring mice to an active nest or fledged young. When owls are not reproductive, they will cache mice to be consumed later.

Adult and subadult owls that are undbanded or have broken bands, as well as fledged young, are captured using noose poles. All individuals are banded with a U.S. Fish & Wildlife Service band on one leg and a color band on the other. Recently, blood samples have been taken from all captured owls to test for West Nile virus.

West Nile virus (WNV) is a mosquito-borne flavivirus that was first introduced on the east coast of North America in 1999 and can cause serious disease in humans and wildlife, especially birds. By 2003, WNV had spread across North America and first appeared in southern California. By fall 2004, WNV had spread into northern California.

The arrival of WNV in northern California could have profound impacts on the extant bird communities, which are naive to the effects of WNV. Although the disease is known to cause mortality in avian species, the potential impacts of WNV on avian populations are largely unknown.

The overall objectives of this research are to 1) link the spatial and temporal effects of WNV and WNV vectors (mosquitoes) with the population dynamics of spotted owls in California, 2) examine these effects in relation to forested landscapes undergoing different forest management practices, and 3) develop statistical and mathematical models useful for predicting both the temporal and spatial effects of WNV on avian populations.

In a broad sense, we believe this system has promise for predicting the effects of WNV and other introduced pathogens on wild avian populations. We believe our research can provide a benchmark in the empirical study of emerging wildlife diseases, elucidating the potential impacts of emerging diseases on naive fauna, and result in optimal management and increased understanding about the dynamics of wildlife-disease systems.

Barred owls have been invading the range of the spotted owl since the 1960's, and first were found in northern California in the 1980's.  They have become an issue of concern in studying and managing for spotted owls as their populations increase because of potential competition between the species.  There is strong evidence that spotted owl populations have decreased in some areas where barred owls have increased.  Direct competition is possible between the species causing spotted owl populations to decrease, but it is difficult to show a direct effect.  It is also possible the barred owls are simply taking advantage of a decline in spotted owls from another cause.  One piece of anecdotal evidence supporting competition is that barred owls appear to be more aggresive than spotted owls, at least vocally if not physically.