Breeding biology of the Oriental White Stork reintroduced in Central Japan — Effects of artificial feeding and nest-tower arrangement upon breeding season and nesting success—

Reintroduction of the Oriental White Stork Ciconia boyciana into Tajima District, Hyogo Prefecture started in 2005 and the population size is increasing with successful breeding in the wild. Our study on the reintro- duced population composed of banded birds evidenced that the pair once formed continues to breed in a same place and the pair-bond continues over years. Eight pairs laid 29 clutches including 3 replacement ones in 5 years between 2007 and 2011. From information on the day of egg-laying, hatching, fledging of these clutches, it was concluded that incubation and nestling periods are 31-35 days and 63-74 days, respectively. Thus it takes about 100 days from egg-laying to fledging of young. Egg-laying started between early March and late April and fledging occurred from mid-June to late July excluding those by pairs that were fed enough artificially. They laid eggs and fledged young exceptionally early. Clutch-size was 3 or 4 in most cases, whereas clutch-size of 6 was available only from artificially well-fed pairs. Success rate of the first clutch of a year to fledge at least one young was 0.65 and the probability of an egg to fledge was 0.34. The average number of fledglings was 1.2 birds per first clutch of the year. Chicks were killed by predators and neighbouring territory owners, and parental infanticide occurred in three nests. The effects of artificial feeding and nest-tower arrangement on breeding are discussed.