Ecology of the Siberian Tit Parus cinctus in Relation to Habitat Quality: Effects of Forest Management

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Abstract
Breeding biology and site tenacity of the Siberian Tit were studied in northernmost Finland in moderately managed and heavily thinned forests. In moderately managed forests nesting success (82%) and number of fledglings/nest (6.6) were significantly higher than those in heavily thinned forests (58% and 5.0, respectively). Nestling starvation accounted for most of these differences, because neither hatching success nor predation pressure differed between the two types of forest. Nestlings had significantly longer wings in moderately managed forests just before fledging at the age of 15 d. Therefore also fledgling mortality is probably higher in heavily thinned areas. Clutch size was slightly higher in the heavily thinned (8.6, N = 26) than in the moderately managed area (8.0, N = 38). This difference was due to 3 d earlier commencement of egg-laying in the former area. Clutch size decreased by 0.12 eggs d-1 with advancing laying date. Mean density of pairs was 4.2 in the moderately managed and 1.5 km-2 in the heavily thinned area. Males, females or pairs moved on the average 430 m (N = 16, range 0-1500 m) between successive breeding seasons. Adult birds had a yearly survival rate of at least 49%. In autumn and winter they were observed within less than 500 m of their earlier breeding site thus indicating that these birds are sedentary. Of the 465 fledglings ringed in 1983-88, only one was later recorded breeding. Heavily thinned areas are suboptimal habitats for the Siberian Tit in terms of density, offspring production, nesting success and fledgling size. In the Siberian Tit, density seems to be a good measure of habitat quality. Lowered nesting success caused by heavy forest management is probably connected with the drastic decline of the Siberian Tit during the past decades.