Food-niche differentiation in sympatric species of kingfishers, the Common Kingfisher Alcedo atthis and the Greater Pied Kingfisher Ceryle lugubris

Abstract

The Common Kingfisher Alcedo atthis and the Greater Pied Kingfisher Ceryle lugubris breed sympatrically along the Chikuma River in central Japan. These kingfisher species differ in body size, with the latter being much larger than the former. To understand the potential mechanisms that might play a role in food-niche differentiation between these two species, we studied their foraging ecology in the breeding seasons of 2005 and 2006. Specifically, we compared the foraging habitat, foraging behavior, and food delivered to nestlings between the two kingfishers. We video-recorded the food delivered to nestlings during the day, and our results indicated that these species differed in their foraging ecology in several respects: (1) Common Kingfishers caught prey at sites where the water flow was calm, while Greater Pied Kingfishers hunted at sites where the water flowed rapidly; (2) Greater Pied Kingfishers dove from a higher position and caught fish in deeper water than Common Kingfishers; and (3) Common Kingfishers preferred smaller fish than Greater Pied Kingfishers. Overall, Common Kingfishers used a wider variety of foraging sites and food types than Greater Pied Kingfishers in the study area. As interspecific territorially and aggressive interactions between the two species were rarely observed, the food-niche differentiation between the two species was not likely the outcome of competitive exclusion. We conclude that the realized food-niches of the two kingfisher species reflect their respective body sizes.