Sexual Dimorphism in Breast Stripe Width and Beak Eco-Morphology in Himalayan Green-Backed Tits (Parus Monticolus)

Abstract

Quantitative field data on sexual dimorphism is scant for most bird species. In this first field study of a western Himalayan population of Green-backed Tits ( Parus monticolus), we demonstrate that breast stripe width is a dimorphic trait that is a reliable measure to sex this species in the wild. Based on our ability to sex the birds in hand, we describe the sexual dimorphism in eco-morphological variables in our study population. Sexual dimorphism in beak morphology changed from winter to summer due to males having shorter beaks (4.5%) in summer; however, there was little change in female beak measurements. Our study on this Himalayan congener of a widely studied European species can be used to inform studies of the evolutionary ecology of morphological traits in closely-related species inhabiting vastly different habitats.