The American Kestrel, a colorful and charismatic falcon, has kept researchers scratching their heads for years. Population declines are confirmed across North America, but who or what to blame has remained elusive. A new paper, "Evidence of Continuing Downward Trends in American Kestrel Populations and Recommendations for Research Into Causal Factors," published in the Journal of Raptor Research, provides needed updates on the status of kestrel populations at the regional scale, and offers a comprehensive discussion on the potential causes for the species' decline. Importantly, the authors point out that kestrels could be experiencing trouble outside of the breeding season, a part of their annual cycle that is arguable understudied. This paper provides an updated common ground for raptor researchers through which they can streamline study priorities, an important recalibration if this beloved falcon is to remain numerous in our skies.
Authors David M. Bird and John A. Smallwood posit that multiple factors are likely causing kestrel declines, evidenced by the fact that, while many populations are declining, some are rebounding or stabilizing. Not all kestrels are encountering the same challenges. Bird and Smallwood present essential research pathways moving forward, including: investigating the impact of Cooper's Hawks on kestrel distributions and survival, assessing habitat degradation on the kestrel's wintering grounds (which often fall outside of U.S. borders), looking at fine-scale changes in habitat quality on the breeding grounds, examining the impacts of climate change on the availability of prey species for kestrels, determining how important grasshoppers are as a prey species, and studying the impacts of rodenticides and pesticides on the health of kestrel populations.
Not only are focused research recommendations put forth in this paper, but several theories about the kestrel decline are put to rest. West Nile virus and competition for nesting cavities from European starlings are no longer considered significant threats to kestrel success.
