The habitat and breeding biology of the Rufous Turtle Dove, Streptopelia orientalis, were studied at agricultural lands with small woods and shelterbelts in the Tokachi District, Hokkaido, for 5years in 1976 and 1979-1982. This dove is a summer visitor, occurring from late March to late October in the study area. At cultivated fields the mean number of the Rufous Turtle Doves based on 16 counts (8 per day) in each month were 5.8 per km in June (sowing season) and 7.6 in September (harvesting season), the numbers being significantly greater than in other months, because they gathered to feed. In woods the mean number was 4.0 per km in May and then decreased. Since the doves nest in woods and feed mainly in cultivated fields, the argicultural land with small woods or shelterbelts was one of their typical habitat.
The doves preferred the nest sites that were well concealed by foliage, i.e. ever-green coniferous trees in April and May, but deciduous trees after June when tree canopies were full. Thirteen species of trees were used for nesting. The tree species most frequenctly selected were Larix leptolepis, Abies sachalinensis, Pinus strobus, Salix spp. and Sambucus sieboldiana. Nests were placed at height between 0.5 and 5.5 m above the ground, of which 80% were between 1 and 3 m. The relationship between tree height (x) and nest height above the ground (y) can be expressed by a regression equation y=0.540+0.416x-0.017x².
Most nests (92%) were placed on 3 or 4 horizontal or near horizontal branches, although 2 to 6 branches were used. New nest was built for each brood except for 4 cases, in which the same was used twice and a nest was built on an old nest of Lanius bucephalus. The nest material most frequently used was dead twins of L. leptolepis, A, sachalinensis, Alnus japonica, Betula platyphylla and Acer ginnala.
The breeding season from the first nest-building to the last fledging was 6 months long, ranging from early April to early October. Although the number of the nests with eggs increased from April and showed a pronounced peak in May and June, there was no apparent seasonal variation in the number of the nests with nestlings. The mean clutch size for 57 nests was 1.9, ranging from 1 to 2. Fresh eggs weighed 11.8g. The incubation commenced with the laying of the first egg and the incubation period was 15 to 16 days. Both sexes participated in incubation. During the incubation period, 33% of nests or 33% of eggs laid were abandoned, and 19% of nests or 20% of eggs laid were destroyed by predators (Mustela sibirica and perhaps Accipiter nisus).
The nestling period was 16 to 17days. The body weight of nestlings varied 9g at hatching to 165g in nestlings 17 days old. The wing length increased from 12mm at hatching to 133 mm in 17days old. The primaries and secondaries erupted from their sheaths in 6 to 7 days old. The sheaths of tail feathers began to appear in 4 to 5days old and the tail length was 70mm in 17days old. The eyes opened in 6 to 7 days old. The body was covered with feathers on 10 to 11 days old, thereafter the parents did not sit on their nestlings.
For the first few days the nestlings were fed on fluid food, but after the 4th day they were fed solid foods, such as grains. After fledging the young were fed for a few days. During the nestling period, 18% of nests or 11% or nestlings were preyed on by predators. The succes of the nests with eggs was 26% and overall breeding snores (fledglings as a percentage of the eggs laid) was 25%.
During the 6-months breeding season, each pair was expected to give an average fecundity of 7.2 clutches, ranging from 4 to 13 clutches. The probability that each pair raises 4 successful broods per season was 0.03. The corresponding values for 3, 2 and 1 successful broods are 0.21, 0.46 and 0.24 respectively.

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