Abstract
It was previously thought that the daily home range of Great Cormorants Phalacrocorax carbo hanedae living at Tokyo's Shinobazu Pond colony was between 30 and 40 kilometers. In this study, however, 7 color—banded cormorants from the Shinobazu Pond colony were verified by observations and recoveries at sites of more than 50 kilometers distant from the colony. All of these birds had been banded and disappeared from the colony between the ages of 2 and 11 months. Distance of observation or recovery sites ranged from 54 to 287 kilometers. 4 of the 7 verifications were from sites of less than 100 kilometers distance, and the birds are thought to have been on short-term foraging forays, and would eventually return to the natal colony. The 3 other verifications, on the other hand, were over 200 kilometers from Shinobazu Pond, and are thought to have dispersed from the natal colony and joined a different flock. There is no other colony or roost within 200 kilometers of Shinobazu Pond. Although the cormorants found in the Kanto Area are considered to be resident, these data indicate that younger birds range further than adults, and may even disperse into other colonies. Mobility and the need to disperse may become greater as population increases and the number of local sub-colonies grows. These conclusions agree with research performed on other species of cormorant.
