Age and sex dimorphism in the Canary Blue Tit <i>Cyanistes teneriffae teneriffae</i> on the island of Tenerife, Canary Islands

Abstract

The Canary Blue Tit Cyanistes teneriffae has recently been split off from the Common Blue Tit Cyanistes caeruleus as a separate species. Live biometrics from across the entire distribution on the island of Tenerife (subspecies teneriffae teneriffae) are reported. Results suggest that first-year birds had similar bill shape to adults but differed in wing length, tarsus, tail and mass, being smaller on average. A high degree of sexual size dimorphism is reported, males being on average larger than females for wing length, bill length, bill depth and tarsus. A classification tree between the sexes showed that wing length and bill depth were the most important variables and correctly classified males in all occasions (i.e. male = wing length >62.5 mm; bill depth >3.7 mm, 100% correctly classified) but for practical sexing in the field it is recommended to use wing length as a reliable sexing criterion (wing length >62.5 = male, 96% correctly classified). This high degree of sexual size dimorphism observed suggests a high sexual selection in the Canary Blue Tit.

OSTRICH 2010, 81(1): 51–57