Sexual Dimorphism in Relation to Winter Foraging and Territorial Behaviour of the Three‐toed Woodpecker Picoides Tridactylus and Three Dendrocopos Species

SUMMARY A comparison of morphological characters shows that Picoides tridactylus is more markedly sexually dimorphic than Dendrocopus leucotos, D. major or D. minor . This is correlated with intersexual differences in foraging behaviour in P. tridactylus , lacking in the Dendrocopus spp. Apparently as a consequence, the sexes are able to share winter territories among P. tridactylus but not among D. major or D. minor ; conclusive observations of D. leucotos were not possible. It is suggested that these differences may reflect the distributional history of the species, and the extent of interspecific competition.