 Analysis of the proportions of the toe bones of the most primitive birds "Archaeopteryx" and "Confuciusornis", compared to those of living species, suggest that the early species may have lived both on the ground and in trees.One study suggested that the earliest birds and their immediate ancestors did not climb trees.This study determined that the amount of toe claw curvature of early birds was more like that seen in modern ground-foraging birds than in perching birds.