BECHARD, M.J., J.H. SARASOLA & A.J. HELBIG. 2004. Morphometric measures of male and female Spot-winged falconet Spiziapteryx circumcinctus sexed using PCR amplification methods. In Raptors Worldwide [R. D. Chancellor and B. U. Meyburg, eds.] World Working Group on Birds of Prey and Owls, Berlin, pp 451-458.

Abstract: The Spot-winged Falconet Spiziapterix circumcinctus is a little-known Neotropical falconid endemic to southern South America. The classification of the species has been controversial due to a lack of information on the species´ morphology. Only a handful of specimens have been obtained to take morphometric measurements and to determine the degree to which sexual dimorphism has developed in the species. In an effort to provide such data, we captured 22 falconets using bal-chatri traps with various mouse and bird lures in La Pampa, Argentina, between 1998-2001. We measured body mass, wingspan, wing chord, tail length, total length, culmen length and hallux length, and obtained blood samples using standard techniques. Body mass, wingspan, wind chord, tail length, total length, culmen length and hallux length averaged 173.5 ± 29.82 g (±SD), 542.5 ± 23.60 mm, 176.6 ± 5.7 mm, 146.4 ± 6.0 mm, 290.7 ± 9.0 mm, 15.2 ± 1.0 mm, and 13.6 ± 0.77 mm, respectively. We sexed 8 captured falconets using PCR amplification of the CDH gene intron of DNA extracted from blood samples. All of the measures taken, except culmen and hallux lengths, were found to be significantly larger in females than in males (P < 0.05), indicating that, like other falconids, the Spot-winged Falconet has developed reversed sexual dimorphism with females averaging 8.4% larger than males for the measurements we obtained. While the diet of the species is poorly documented, the degree of sexual dimorphism that has developed in the bird indicates that the Spot-singed Falconet is probably rather omnivorous, eating a variety of prey species ranging from insects to lizards and birds.

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