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Nesting Site of Stonechats in a Bog after a Spring Fire

1991; Ornithological Society of Japan; Volume: 40; Issue: 1 Linguagem: Inglês

10.3838/jjo.40.33

1881-9710

Yuzo Fujimaki, Yuri B. SHIBNEV,

Geology and Paleoclimatology Research

The Stonechat Saxicola torquata nests in ground vegetation (CRAMP 1988).Ninety two nests found in agricultural lands of Obihiro and its neighboring areas, eastern Hokkaido, were built in grasses or herbs.In agricultural lands only dead grasses are available for nest covers in late April and early May when Stonechats begin to build the nest for the first breeding.Therefor, they nest in the recess on a slope of ditches covered wilt dead grasses or at base of the clump of dead grasses in pastures.As GREIG-SMITH (1984) indicated, characteristics of nest cover affect breeding success and the presence of vegetation covering the nest is indispensable for the nest building of Stonechats.If there is no ground vegetation available for nest covers, which type of nesting site is selected by Stonechats?We observed their nesting sites and nest construction in the condition lacking available ground vegetation after a spring fire in the Bikin-Alchan Mar (46043'N, 134029'E), northern Primorski krai, USSR, in June 1990.The Bikin-Alchan Mar is situated between the Bikin River and the Alchan Rriver, and occupies an area of 225,000 ha.Most of the area is a mosaic of bogs covered with sedge and graminoid grass (mainly Calamagostis langsdorffii) tussocks, shrub-grasslands covered with tall grasses and herbs, isolated woods dominated by oaks Quercus mongolica, and ponds.Isolated woods and shrub-grasslands occur on dry parts elevated 1 to 2 m from the bog level.In early May 1990, before the start of our observation, the study area was burnt in a wild fire.After the fire dead grasses and herbs were completely eliminated from the ground surface, and stems of shrubs died in the study area.All 6 nests found in early June were in the upper part of well developed tussocks of sedge or graminoid grasses in the bog area.The entrancee of the nest was concealed well with grown vegetation.In 5 nests young fledged successfully between 10 and 15 June.Since the breeding cycle of Stonechats from nest-building to fledging is about 37 days (CRAMP 1988), it is estimated that they started nest-building in early May, just after the fire.Another nest was destroyed probably by a predator during the nestling period.This nest did not differ form the others in nesting site type.After young left the nest, we cut tussocks by a saw to get profiles of the vertical section.All 5 nests examined were built near the entrace of old tunnels of voles Microtus fortis (Fig. 1).Nest cavities were 8 to 10.5 (9.3 in average) cm high, 9 to 10 (9.4 in average) cm wide and 8.5 to 11 (9.4 in average) cm deep, and were situated at a little inside of the tunnel entrance.The bottom of nest cavities was a hollow of 3 to 4 (3.4 in average) cm deep.The height and width of entrance were 6 to 7 (6.2 in average) cm and 5 to 6 (5.8 in average) cm respectively, being sinificantly smaller than those of the nest cavities (MANN-WHITNEY'S U-test, P<0.01).Larvae of bird-parasitic blowfly Protocalliphora sp. were found in all nests examined.The blowfly parasitizes nestlings of cavity-nesting passerines which build nests with great amount of materials (PINKOWSKI 1977).Blue-and-white Flycatcher Cyanoptila cyanomelana, Great Tit Parus major, Russet Sparrow Passer rutilans, Tree Sparrow P. montanus and Red-cheeked Myna Sturnus philippensis have been recorded as the host of the blowfly (UCHIKAWA 1966, HORI & IWASA 1988).Other than these species, host birds have not been known.Larvae of blowfly were not found from 61 Stonechats' nests in which young fledged successfully in agricultural lands of Obihiro and its neighboring areas.These findings suggest that nesting sites selected by Stonechats in the study area differ from those found in Obihiro in respect of habitats of the blowfly.