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Cavity size, clutch‐size and the breeding ecology of Tree Swallows Tachycineta bicolor
Author(s) -
RENDELL WALLACE B.,
ROBERTSON RALEIGH J.
Publication year - 1993
Publication title -
ibis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 80
eISSN - 1474-919X
pISSN - 0019-1019
DOI - 10.1111/j.1474-919x.1993.tb02848.x
Subject(s) - avian clutch size , nest box , brood , biology , ecology , nest (protein structural motif) , reproductive success , clutch , zoology , predation , reproduction , population , demography , biochemistry , physics , sociology , thermodynamics
Previous studies provide evidence that cavity size influences clutch‐size and reproductive success in some hole‐nesting birds, because overcrowding in cavities may cause brood mortality due to trampling or hyperthermia. We tested this hypothesis with two experiments at nestbox populations of Tree Swallows Tachycineta bicolor in southeastern Ontario. Female Tree Swallows showed a preference for nesting in large boxes over small ones in the first experiment, and they laid significantly smaller clutches in small nestboxes during both experiments. Differences in clutch–size between large and small nestboxes could not be attributed to other factors known to influence clutch‐size in birds (e.g. parental quality, habitat quality, laying date). Reproductive success, however, did not differ between pairs using the two box types during either experiment, nor did it differ during within‐clutch‐size comparisons between box types. Some measures of nestling quality were significantly lower for broods in large boxes, but during most comparisons there were no differences. These results do not support the adaptive reason for why cavity size affects clutch‐size. We suggest that broods in our experiments did not experience the microhabitat conditions necessary to induce the expected differences in brood mortality.