Ecology of the Siberian Tit Parus cinctus in NW Finnish Lapland

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Abstract
The ecology of a population of Siberian tits nesting in nest-boxes was studied in mountain birch forest at Kilpisjarvi (about 69.degree.03''N, 20.degree.50''E) in 1966-1980. The annual number of breeding pairs averaged 2.1 .+-. 1.1 (SD), or 0.4 pairs km-2. The coefficient of variation in density was 52%. Partly due to the narrow study area, the average distance between the pairs was 3.2 .+-. 1.5 km. Old individuals seemed to be more site-tenacious than 1st-breeders. The mean date of laying of the 1st egg was May 25 .+-. 10 days, the mean air temperature then being 2.9 .+-. 3.2.degree. C. The average clutch size was 8.0 .+-. 1.9 eggs and the number of fledged young 4.8 .+-. 3.4 per nest. The largest clutches produced most fledglings per nest. The clutch weight averaged about 79% of the female''s body weight. The average adult biomass of 11 g km-2 produced about 29 g km-2 of unhatched eggs, dead young and fledglings.