A Study on Breeding Ecology of Oystercatcher (Haematopus ostralegus) at Yubu Island

A survey of the breeding ecology of Oystercatcher (Haematopus ostralegus) inhabiting in the Youbu Island was conducted from February to August 2006. The maximum number of Oystercatcher was 2,500 in February and the minimum 150 in July. The nests had outer diameter of 191.7±6.14 mm, inner diameter of 127.3±3.90 mm, depth of 34.2±16.2 mm, and had far from high tide of 617.2±302.0 cm. The laying of eggs starts at the early April with average incubation of 29 days. The total number of eggs laid was 168, and the clutch size was 2.47±0.89. The eggs had a major axis of 57.51±0.06 mm, minor axis of 39.15±0.34 mm, and the weight was 44.30±0.26 g. The hatching success rate among 168 eggs was 78.6% (132 eggs), and the fledgling success rate was 9.8% (13 eggs). During the period of study, there were disturbance factors on 105 occasions and it was accounted for 54.3% by other birds, 14.3% by fishermen, 10.5% by fish boat and 20.9% by other causes.