A comparison and analysis of the post-release movement of four species of raptors

Forty individuals of four species of raptors, Cooper's Hawk (Accipiter cooperii), Red-tailed Hawk (Buteo jamaicensis), American Kestrel (Falco sparverius), and Prairie Falcon (Falco mexicanus) were released after a conditioning period and monitored with the use of radio telemetry. All birds were found to generally increase their activity range over a period of time. Juveniles always moved more than adults. Species that consumed greater proportions of avian prey showed increased differences between juvenile and adult movement suggesting intraspecific predation and consequent adaptive significance in increased juvenile movement. Cooper's Hawks showed the greatest movement followed by American Kestrels and then Prairie Falcons. Red-tailed Hawks showed least movement. In species where the sexes may winter together (Red-tailed Hawk and Cooper's Hawk), both sexes appeared to move the same amount. Both species of Falco had increased male movement. The presence of the radio package had no effect on the birds' activity as long as it remained below 4% of the birds bodyweight. Modified falconry techniques as a method of conditioning appeared to adequately prepare each raptor for survival once released.

Le relazioni