Head-bobbing patterns, while walking, of Black-winged Stilts Himantopus himantopus and various herons

Abstract

Head bobbing patterns of walking Black-winged Stilts Himantopus himantopus and eight species of herons were studied. Though several of the species studied had been previously reported as non-bobbing birds, all nine species usually head bobbed while walking during our observations. The head-bobbing pattern most frequently observed was ‘one bob per step’ in which a bird bobs its head once for each step it takes. In several species, one of two other patterns was also observed. The ‘one bob per two steps’ pattern was observed in three species of herons when they were walking slowly, and the ‘two bobs per step’ pattern was observed in Black-winged Stilts. Non-bobbing walking was observed in Japanese Night Herons Gorsachius goisagi walking at relatively fast speed during foraging, and in two other species of herons when they were not foraging. Head bobbing may be affected by walking speed and by whether birds are foraging or not.