Experiments on Population Regulation in Two North American Parids
1979; Wilson Ornithological Society; Volume: 91; Issue: 2 Linguagem: Inglês
ISSN
1938-5447
AutoresFred B. Samson, Stephen J. Lewis,
Tópico(s)Ecology and Vegetation Dynamics Studies
ResumoTwo major hypotheses to explain annual fluctuations of avian populations have emerged from long-term studies of the Great Tit (Parus major) in England (Perrins 1965, Lack 1966) and the Netherlands (Kluijver 1951, 1971; Kluijver and Tinbergen 1953). Lack (1966) argued that annual changes in Great Tit breeding populations reflected mortality of immatures due to starvation between leaving the nest and early winter, whereas Great Tit numbers in Holland according to Kluijver (1951, 1971) were regulated by a behaviorally induced emigration in fall rather than by direct starvation. Although natality often is variable in Great Tit populations from year to year, neither hypothesis considers variation in reproduction directly responsible for changes in breeding numbers. Nor does it appear that spring territory acts as a major density dependent factor regulating a population of the Great Tit (Krebs 1971) or of 2 other European parids, the Crested Tit (P. cristatus) and Willow Tit (P. montanus) (Cederholm and Ekman 1976), but controversy remains (Slagsvold 1975). Although several North American parids have been intensively studied (Odum 1941, 1942; Dixon 1963; Smith 1972, 1976; Glase 1973), it remains unclear what factors influence annual changes in their numbers. The purpose of this study was to experimentally test Lack's and Kluijver's hypotheses on populations of the Black-capped Chickadee (P. atricapillus) and Tufted Titmouse (P. bicolor) in central Pennsylvania.
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