The effect of age and sex on wing morphology and body size of the Bearded Tit Panurus biarmicus in relation to complete moult

In sedentary birds, variation in wing morphology as a result of complete moult during the transition from juvenile to adult plumage is poorly understood. The aim of this study was to characterise sex- and age-related differences in wing morphology resulting from a complete post-juvenile moult in an isolated, sedentary population of the Bearded Tit Panurus biarmicus at El Hondo Natural Park reedbeds (SE Spain). Variation in wing morphology was evaluated by means of a Size-Constrained Components Analysis (SCCA) of standardised primary lengths of 66 birds trapped for ringing. Wing traits representing size and shape showed differences among age and sex classes, adults having significantly greater wing sizes than juveniles and males less rounded or convex wings than females. Structural body size also varied significantly among sex classes, females being smaller than males. Sex- and age-specific differences in wing morphology of these Bearded Tits may represent adaptations to the sedentary and colonial behaviour of the local population within constraints imposed by a reedbed microhabitat.

Ignacio Garcia Peiro, Franciso Robledano and Miguel A. Esteve, Ringing & Migration (2006) 23, 101-106