Ten Years of the Santa Cruz Flats Raptor Count

Articles | By Doug Jenness | Accepted October 01, 2015

Between 2006 and 2015, I coordinated an annual one-day January raptor count at the Santa Cruz Flats. Teams of volunteers surveyed designated sections of the 900 km² area. The goal was to determine which raptor species winter there, their relative numbers, and population trends over time. This paper evaluates the data collected for 20 species of raptor. Although the 10-year time span is too short to identify any definitive trends, over the last five years of the count there were declines in the numbers of three species—28% decline for Northern Harrier (Circus cyaneus), 17% for American Kestrel (Falco sparverius), and 13% for Red-tailed Hawk (Buteo jamaicensis). White-tailed Kite (Elanus leucurus) and Barn Owl (Tyto alba), observed in the first years of the count, have not been reported since 2009 and 2012, respectively. The mean for Crested Caracara (Caracara cheriway) has increased 28% over the most recent five years of the count. For most species, the annual difference was too small to suggest any trends. The survey will be continued to obtain data over a longer time period.