Abstract:
"I evaluate the claim that northern goshawk (Accipiter gentilis atricapillus; hereafter referred to as goshawk) populations are declining in North America based on a reviews of the published literature and analysis of demographic data collected on two goshawk populations in New Mexico and Utah. Evidence of a decline would include range contractions, temporal decreases in density, fecundity, and/or survival, and/or a negative rate of populations change. The goshawk is a former Category 2 species as determined by the US Fish and Wildlife Service and two petitions have been submitted to list the goshawk as threatened or endangered under the US Endangered Species Act. The petitions claimed that goshawks suffered significant declines in the US because of logging practices and were threatened with extinction as a result of over-harvest. There is no evidence of range contractions in western North America and the goshawk's range appears to be expanding (perhaps due to reoccupancy of former range) in the eastern US. The majority of data on abundance of breeding pairs indicate that goshawk densities are highly variable spatially and temporally. There is some evidence to suggest that abundance is correlated with food availability. One study claims that goshawk abundance has declined in the past several decades in northern Arizona but the conclusions are based on an inadequate sampling design. Fecundity fluctuates widely but there is no evidence of a negative trend. Fecundity is apparently influenced by a combination of food availability and predation rates. Survival estimates are too limited to analyze for temporal trends and, as a result of insufficient survival data (l) have not been estimated for any North American goshawk populations. I conclude there is no strong evidence to support the contention that the goshawk is declining in the US. This result can be interpreted either that goshawk populations are not declining or goshawk populations are declining but the declines have not been detected with current sampling techniques (Type 2 error). These two hypotheses cannot be rigorously evaluated with existing published information and will probably not be evaluated in the future with data sets from a single study area because of sampling limitations. To rigorously and objectively evaluate the population trends of the North American goshawk in a timely and construction-effective manner, I recommend a meta-analysis be conducted of all existing published and unpublished data sets."

Summary
This paper evaluates the ESA petitioner's claim that goshawk populations are declining in North America. Kennedy uses data from currently published literature to conduct a demographic analysis on this population. She hypothesizes that if the population is declining, she would detect a range contraction, temporal decrease in fecundity, density, and/or survival, and/or a negative rate of population change. She found no evidence for a contracting range, but found that the range is possibly expanding. She found that goshawk densities (abundance) are highly variable, and show no downward trend. Survival estimates she evaluated were too limited to draw conclusions from. Her conclusion that there is no strong evidence to support the contention that US goshawk populations are declining can be interpreted in two ways: ; 1) goshawk populations are not declining; or 2) they are declining, but we are not detecting the decline. She recommends a meta-analysis be conducted of all existing published and unpublished data sets.