Publication Date

January 2013

Comments

The Journal of Raptor Research is published by The Raptor Research Foundation, http://www.raptorresearchfoundation.org/. Full-text access provided with permission.

Abstract

We use five years of data from 18 routes surveyed to determine the temporal stability of a first reported 100 years pattern, and reconfirmed that the abundance of winter 50 years ago tailed Hawk and American Kestrel decreases with increasing latitude, being more high in the central regions of Illinos in the northern regions. Trained volunteers conducted sampling ( n  = 143) a month driving along selected routes from December to February, from 2004-2005 to 2008-2009. We found significant increases in the abundance of both species from the northern regions to the central regions of Illinois. No significant effects of the year or the month were evident in the abundance of B. jamaicensis (overall mean = 147.2 individuals B. jamaicensis / 1000 km) and the abundance of F. sparverius (overall mean = 51.1 individuals of F. sparverius / 1000 km). 78% of individuals of B. jamaicensis identified by age class, 10% were juveniles and 90% were adults. 80% of individuals of F. sparverius identified by sex, 64% were male and 36% were females. Our findings indicate that there has been a temporary stability of 100 years in the pattern of increased winter abundance of both species from the north to central Illinois, despite substantial changes in both the habitat and farming practices during the past 50 years.

Disciplines

Biology | Ecology and Evolutionary Biology | Ornithology | Poultry or Avian Science | Zoology

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