Friday, July 04, 2008
Determining Sex of Swainson's Hawks in Idaho
Swainson's hawks migrate long distances and are often studied both on their breeding grounds in North America and on their wintering grounds in South America. Male and female Swainson’s hawks have similar plumages, and ecologists need a quick method to determine sex when they are unable to use genetic techniques. In a new study co-authored by USGS wildlife ecologist Michael Kochert, the combination of body mass, footpad length (middle toe tip to hind toe tip), and wing chord (wrist joint to tip of longest primary feather) was the best predictor of sex of Swainson’s hawks in Idaho. Using a combination of measurements was more accurate than single measurements. Body mass was the least accurate predictor because it could vary by time of year, bird condition, and whether the bird had just fed. Molt and feather wear can affect the accuracy of wing chord measurements.
Kochert, M.N., McKinley, J.O., 2008, Use of body mass, footpad length, and wing chord to determine sex in Swainson's hawks: Journal of Raptor Research, v. 42, no. 2, p. 138-141. [FullText] Catalog No: 1821
Contact:
Michael
Kochert,
FRESC,
208-426-5201,
mike_kochert@usgs.gov
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