Diet of Osprey during a breeding season in coastal Iwate Prefecture, Northern Japan

Abstract

To clarify the feeding habits of Osprey Pandion haliaetus in coastal areas of Iwate Prefecture, we set a camera in two nests during the breeding season of 2018 and analyzed the prey items recorded. We identified fishes to family or order levels, measured their total length, and estimated their weights based on values reported in the literature. In the two nests, Beloniformes was the most frequently observed order, and Scombridae, Cyprinidae, Carangidae, and Mugilidae were also delivered frequently to the chicks. The families of fishes that had the highest estimated weights were Scombridae and Mugilidae, suggesting that they are important food resources for chick growth. Many of these fishes live at the sea surface, in shallow water, or in mild currents, which corresponded to the known hunting behavior of Osprey, which hunt fish swimming near the water surface. The Osprey in this study fed on seasonally available saltwater fish, with the exception of Carp families. Of Carp, Tribolodon and Carassius, which inhabit the freshwater and marine coastal areas, respectively, were major prey items delivered to osprey nestlings. The estimated weight per feeding was significantly larger in both pairs during the late rearing period. Based on the habitat characteristics of the fish that Ospreys delivered to the nest, the bays and estuaries were the main fishing areas. At present, there is a concern about the deterioration of the fishing habitat for Ospreys, due to the reconstruction project after the major Tohoku Earthquake in 2011.