The austral peregrine falcon (Falco peregrinus cassini) was studied in the Andean foot- hills and across the Patagonian steppe from November to December 1981. The birds under study (18 pairs) were reproducing at or near normal (pre-DDT) levels for other races. Pesticide residues, while elevated, were well below the values associated with reproductive failure in other populations. With one exception, eggshells were not abnormally thin. The peregrine falcon in Patagonia exhibits extreme color variation. Pallid birds are nearly pure white below (light cream as juveniles), whereas normally pigmented birds are black-crowned and conspicuously barred with black ventrally. Rare individuals of the Normal Phase display black heads, broad black ventral barring, and warm reddish-brown ventral background coloration.
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The austral peregrine falcon: Color variation, productivity, and pesticides