Breeding ecology of the Streaked Shearwa-ter at Kamurijima I

Abstract

1. The breeding ecology of Calonectris leucomelas at Kamurijima I. on the Japan Sea coast of Honshiu is reported based on 20 visits and 42 days of research. Specimens strayed into inland during post-breeding season was also studied.2. Breeding season sets in from late February and the island is abandoned from early to late November.3. They feed on the ocean during the day, returning to the island one hour after sunset and leaving again one hour before sunrise. The night number of birds on the island varies by night ranging 30, 000-36, 000.4. Preparatory period is from early March to late May during which nestoccupation (old-nests), nest-amendation and forming laying bed with dead leaves are done.5. Total number of nest-hollows on the island was around 128, 000 but usable and actually used nests are about 98, 000 of which only some 12, 000 were breeding nest-hollows. 6. A white egg is laid in middle and late June, measuring 42.0-47.0×64.0-72.2mm., 80g. Total egg number was assumed as 12, 000.7. Incubation period more than 51 days; the hatching dates ranging between August 10 and 20. The new born chicks measure: culmen 20-24 mm, wing 28-33mm, tarsus 19-25mm, middle toe 12-24mm, weight 50-70g.8. The chick is fed once at night and grows at a rate of about 20g per day until middle October, the maximum being 990g. At 30-40 days, the culmen 42-50mm, wing 115-163mm, tarsus 50-60mm, middle toe 55-67mm, weight 515-740g were measured; and at 60 days, culmen 43-57mm, weight 360-990g.9. In middle October, feathers and quills become developed and the feeding by parents become irregular and the weight of chick decreases, though it assumes adult-like feature.10. The chicks leave the island during late October and middle November. The feeding period is 70-100 days with average of 80 days. The chick weight at flying is less than 500g, some still with some down.11. The adult birds leave the island first and the chicks follow them as they grow.12. In early and middle November not few of them are found strayed in the prefectures Kyoto, Fukui, Osaka, and Shiga and these include young of the year and weekened adult birds, just started for migration.13. One hundred chicks and 22 chicks were banded in October 1960 and November 1961 respectively. None of the 1960 chicks recovered in 1961. More banding is being planned.