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Abstract
Tropical owls, being poorly studied, have been excluded from discussions of reversed size dimorphism. As part of a breeding and food habits study, we weighed and measured 20 Mottled Owls (
Ciccaba virgata) and a mated pair of Black-and-white Owls (
C. nigrolineata) in northern Guatemala. Mottled Owls exhibited pronounced dimorphism with respect to body mass, wing chord, and tail length. A mated pair of Black-and-white Owls was also quite dimorphic with respect to body mass. Mate choice in six pairs of Mottled Owls was not correlated with size (mass or wing chord). Since both species are highly insectivorous, they do not fit an alleged trend among owls toward increasing dimorphism with increased reliance on vertebrate prey. Indeed, our results are at odds with important assumptions or predictions of numerous hypotheses regarding the evolution of reversed size dimorphism in owls.
Parent Publication
Citation
Gerhardt, Richard P.; Gerhardt, Dawn McAnnis. 1997. Size, dimorphism, and related characteristics of
Ciccaba owls from Guatemala. In: Duncan, James R.; Johnson, David H.; Nicholls, Thomas H., eds. Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium. Gen. Tech. Rep. NC-190. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. 190-196.
