Abstract
We compared the leg structure of 174 Marsh Tits Poecile palustris and 95 Willow Tits P. montanus from Hokkaido, Japan. Overall, the Willow Tit had a significantly longer hind claw, middle claw, and tarsus than the Marsh Tit. In Marsh Tits, 99% of the hind claws were 7.1 mm long or less, and tended to have a strong curvature with a blunt tip. But in Willow Tits, 98% of the hind claws were 7.2 mm long or more, and tended to have a weak curvature with a sharp tip. Therefore, these hind claw characteristics are very effective as criteria for species separation, regardless of age or season.
