HIGH RETURN RATES FOR RELOCATED RED-TAILED HAWKS: PRELIMINARY FINDINGS AT PORTLAND INTERNATIONAL AIRPORT

Pacific Habitat Services, Inc. (PHS), under contract with the Port of Portland (Port), trapped, banded, and relocated red-tailed hawks at the Portland International Airport (PDX) in Portland, Oregon, beginning in October 1999. Although the Port has a program to deal with wildlife hazards to aircraft operations, raptor prey base management and hazing hadn’t effectively reduced wildlife hazards. Nineteen birdstrikes occurred in September, 1999. Prior to this season, birdstrikes ranged from 0 to 11 within a one-month period. Thus, immediate action was needed to reduce raptor abundance on the airfield. In fall and winter of 1999, PHS captured and relocated fifteen hawks, primarily red-tailed. Six were adult birds and 9 were hatch-year birds. A minimum of 5 adult and 4 hatch-year hawks returned after relocation. This rate of return is much higher than that reported by Wernaart et al. (1999), who reported a return rate of only 4% with birds moved similar distances at Canadian Airports. A low return rate was also reported by wildlife personnel at Chicago O’Hare Airport. A likely factor in the high initial return rates is the geography of the PDX area. Hawks may navigate using landscape features such as the Columbia River, the Willamette River and the Cascade Mountains. Continued wildlife surveys on the airfield and color banding also suggest that PDX may support a higher population of resident, non-migratory hawks than airports in other locations