Kinematic parameters of the walking of herons, ground-feeders, and waterfowl.

The kinematic gait characteristics of six species of birds in three groups were compared. The groups studied were herons (Gray Herons and Little Egrets), ground-feeders (Domestic Pigeons and Gray Starlings), and waterfowl (Pintails and Black-headed Gulls). The results showed that the relative stride frequency was greater in the waterfowl than in the other species. Complementary to this, the amplitude of the movements was smaller in the waterfowl than in the others. These differences between the waterfowl and the other species might be caused by their morphological and/or physiological adaptation to swimming. Another possible cause for these differences was the magnitude of head bobbing, as the ground-feeders and herons, which walk with head bobbing, showed a large relative stride length and excursion angle, while the waterfowl, which do not head-bob, walk with a relatively short stride length and small excursion angle. Moreover, the relative magnitude of head movement during walking was especially large in Little Egrets, which showed an especially large relative stride length and excursion angle. These parameters may have some mechanical relationships with each other.