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Post-Migration Weight Gain of Swainson's Hawks in Argentina

Michael I. Goldstein, Peter H. Bloom, Jose H. Sarasola and Thomas E. Lacher
The Wilson Bulletin
Vol. 111, No. 3 (Sep., 1999), pp. 428-432
Stable URL: http://www.jstor.org/stable/4164111
Page Count: 5
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Post-Migration Weight Gain of Swainson's Hawks in Argentina
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Abstract

Swainson's Hawks (Buteo swainsoni; Aguilucho Langostero) were captured and banded in La Pampa, Argentina from 28 November 1996 through 25 January 1997. We collected morphometric measurements to determine if hawks gained weight on the austral (non-breeding) grounds. Hawks in apparently healthy condition weighed 819.7 ± 11.1 g (mean ± SE, n = 127, range 540-1090 g). Weight increased significantly over the length of the non-breeding season in Argentina (P = 0.0059), but wingspan (124.9 ± 0.5 cm, n = 127, range 105.7-137.1 cm) and tail (19.8 ± 0.1 cm, n = 127, range 16.5-23.1 cm) did not. When separated by age, weight increased significantly for juveniles (P = 0.0083) but was marginally non-significant for adults (P = 0.0555).

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