BREEDING SEASONS OF THE HOUSE SPARROW AND TREE SPARROW PASSER SPP. AT OXFORD |
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Authors: | D C Seel |
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Institution: | Edward Grey Institute of Field Ornithology, Botanic Garden, Oxford. |
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Abstract: | The breeding season of P. domesticus in 1961 and from 1963 to 1964. at Oxford began in April and ended in early August; that of P. montunus began slightly later and ended slightly earlier and this species also laid fewer clutches. In P. domesticus laying birds fell into two groups, namely "early-" and "late-starters", which, from a comparison with data obtained from birds of known age, appeared to be mostly females two or more years old, and females one year old, respectively. In P. montanus , however, it appeared that birds of all ages were beginning breeding at about the same time in the season. The laying of first clutches of the early-starting birds of P. domesticus and of the earlier starting members of the one group of P. montanus was correlated with the prevailing air temperature; it is estimated that P. domesticus began its laying at slightly lower air temperatures than P. montunus . It is suggested that laying is adapted to begin at a particular air temperature because at lower temperatures the adult would have insufficient energy available to produce and incubate a clutch. |
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