巣箱を利用したフクロウのヒナの標識および育雛時の餌内容

Abstract

Niigata Prefecture is located along the Japan Sea side of central Honshu, Japan. In this research on Ural Owl, nesting boxes were set out in Japanese black pine (Pinus thunbergii) woodlands along the coast. A total of 50 boxes were provided from 1996 to 2005, set at heights of 2.5 to 3.5 meters, and at intervals of 20-1,000 meters. Twenty of boxes were utilized by breeding Ural Owl. A total of 43 chicks were taken, weighed, banded and returned to their nest. Weight ranged from 240-615 grams. In addition, remains of food were analyzed. During the first week after hatching, remains of Japanese Robin, Blue-and-white Flycatcher and Narcissus Flycatcher were common. These songbirds are on the northern migration just as the chicks hatch out in late April to early May, and are thus readily available in the local area. In addition, these small prey may be easy to the young chicks to digest. Once the chicks have grown to over 400 gr., the size of food items tends to increase, including Whites's Ground Thrush, Starling, Brown-eared Bulbul, Japanese Grosbeak and also Norway rat (Rattus norvegicus). As the chicks grow further doves and pigeons are added. Feeding appears to stop about 5 days before fledging, after which the weight of the chicks drops by 80-100 grams. For the first two weeks after exiting the nest, the fledglings perch on branches within a 30 m radius of the nest, and are fed mostly between midnight and 1200 hrs.