Bill Crossover Ratios in Canadian Crossbills Loxia spp.

Publication Type:Journal Article
Year of Publication:1987
Authors:James, PC, Barry, TW, Smith, AR, Barry, SJ
Journal:Ornis Scandinavica
Date Published:1987
ISBN Number:00305693
Keywords:Canada, Fringillidae, Loxia, Loxia curvirostra, Loxia leucoptera
Abstract:The relative direction of crossing of the upper mandible with respect to the lower was recorded in 383 Crossbills and 322 Two-barred Crossbills collected in Canada. There was no significant difference between the occurrence of right-billed and left-billed Crossbills, but a highly significant excess of left-billed Two-barred Crossbills existed. In both species, the direction of bill crossing was independent of sex, age, and geographic locale. It is suggested that these ratios may be related to those of two distinct seed cone morphologies described in several coniferous tree species.
Short Title:Ornis Scandinavica
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