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1 March 2006 Fitness Level as a Determining Factor in the Survival of Rehabilitated Peregrine Falcons (Falco peregrinus) and Brown Goshawks (Accipiter fasciatus) Released Back Into the Wild
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Abstract

This study examined the effect of 2 fitness programs on the postrelease survival and ability to maintain weight of 15 peregrine falcons (Falco peregrinus) and 12 brown goshawks (Accipiter fasciatus) held captive for treatment or because they had been orphaned. Each bird was treated or allowed to mature, then was either exercised by traditional falconry methods or by stimulating flight within its cage. Prior to release, resting blood lactate concentrations were measured before a short period of exercise and at 2 and 10 minutes after a standardized exercise test. Pre-exercise blood lactate concentrations were higher in cage-exercised peregrine falcons compared with those exercised by traditional methods, but there was no difference in pre-exercise lactate concentrations between the 2 treatment groups of goshawks. At 2 and 10 minutes following exercise, blood lactate concentrations were significantly higher for the cage-exercised group of both species. All birds were fitted with radiotransmitters, released, and monitored, then were trapped at varying times after release and weighed. Of the falconry-trained birds, 3 of 6 peregrine falcons and all 4 brown goshawks gained weight. In contrast, all 9 peregrine falcons and 6 of the 8 brown goshawks subjected to cage exercise lost weight postrelease. The results suggest that peregrine falcons and brown goshawks exercised with traditional falconry techniques were more fit than the same species of birds exercised in their cages and that the improved fitness achieved with the former method increases the probability that captive peregrine falcons and brown goshawks will survive after being released to the wild. The study also indicates that postexercise blood lactate concentrations are important predictors of fitness in raptors.

Peter H. Holz, Richard Naisbitt, and Peter Mansell "Fitness Level as a Determining Factor in the Survival of Rehabilitated Peregrine Falcons (Falco peregrinus) and Brown Goshawks (Accipiter fasciatus) Released Back Into the Wild," Journal of Avian Medicine and Surgery 20(1), 15-20, (1 March 2006). https://doi.org/10.1647/1082-6742(2006)20[15:FLAADF]2.0.CO;2
Published: 1 March 2006
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