Ardea
Official journal of the Netherlands Ornithologists' Union

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Lack D. (1958) A quantitative breeding study of British Tits. ARDEA 46 (3-4): 91-124
1. Results for four further years supplement an earlier study. 2. Annual fluctuations in the number of breeding pairs were irregular. Those of the same species in different woods and of Great and Blue Tits in the same wood were usually correlated. Those of the Great and Blue Tit were of similar magnitude in rich and poor habitats. 3. The mean date of laying varied markedly from year to year, due to variations in the mean temperature, especially in the second half of March and early April. In some but not other years, the time of laying differed greatly in different woods, for unexplained reasons. Laying started consistently earlier in gardens than woods, and consistently later in Corsican than Scots Pine. 4. A small decline in mean clutch-size during the main laying period occurred each year in the Blue Tit, in about half the years studied in the Great Tit, but not in the Coal Tit. In all years late layings of the Great and Blue Tit were much smaller than those started in the main laying period, but in the Coal Tit early repeat clutches were a little larger than first layings, though late repeats were rather smaller. 5. Marked annual differences in the mean clutch-size in the main laying period were due to two factors, first to a tendency, found in the Great and Blue Tits but not in the Coal Tit, for clutch-size to be higher when the mean date of laying was earlier, and secondly to an inverse correlation in all three species between clutch-size and population density. 6. The mean clutch-size was smaller in gardens than woods, smaller in Corsican than Scots Pine, and there were other variations with the type of habitat. 7. Hardly any nestling Great and Blue Tits starved in broad-leaved woods, but some did so in gardens and many did so in conifers. The Coal Tit, though primarily adapted to conifers, raised nearly all its young in broad-leaved woods. There was occasional heavy predation by Weasels. 8. Second broods were uncommon in all three species.


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