Distribution and movement patterns of individual crested caracaras in Calfornia

摘要

There are now numerous records of the Crested Caracara (Caracara cheriway) from California and elsewhere well north of its breeding range, but whether or not they represent wild birds or escapees from zoos or falconers has been debated. Through 2011, the California Bird Records Committee (CBRC) had accepted 49 records that they considered to represent naturally occurring vagrants, but decisions concerning the number of individuals involved in these records were haphazard. Therefore, we assessed the date, location, age, molt status, and appearance of caracaras representing 60 observations specific to date and location in California and propose that these records involve only 11 individuals, recorded between 1 and 34 times throughout the state; a twelfth individual was recorded from December 2011 to April 2012. Our 11-bird scenario was proposed and accepted by the CBRC in January 2012. This synthesis clarifies the species' pattern of occurrence in California: ten of the 11 individuals were first detected in fall or winter, eight individuals were first detected in their first or second years, four of these eight were later detected at appropriate ages elsewhere in California, and six individuals moved north within the state. These patterns are consistent with birds moving north as wild vagrants and so support the CBRC's decision to accept the Crested Caracará as a naturally occurring species. We hope that our analysis will help other records committees evaluate the status of this species in other regions, perhaps revealing a similar pattern of natural vagrancy throughout North America.