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MASS LOSS IN BREEDING HOUSE WRENS:EFFECTS OF FOOD SUPPLEMENTS
Author(s) -
Cavitt John F.,
Thompson Charles F.
Publication year - 1997
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/0012-9658(1997)078[2512:mlibhw]2.0.co;2
Subject(s) - troglodytes , biology , ecology , seasonal breeder , breeding pair , national nature reserve , zoology , demography , nature reserve , population , sociology
Adult passerines commonly lose mass during the course of the breeding cycle. This loss has been ascribed to an energy deficit incurred during nesting, but recently two adaptational hypotheses have been proposed. The first, the wing‐loading hypothesis, proposes that adults actively reduce mass in order to increase flight efficiency. The second, the reserve‐mobilization hypothesis, proposes that females store reserves during the early stages of the breeding cycle, which they mobilize to sustain them during later stages. We tested these hypotheses by providing food supplements to House Wrens ( Troglodytes aedon ) breeding on a study area north of Bloomington, Illinois, during the 1990–1992 breeding seasons. Additional food had no effect on mass except late in one season. Females that were given additional food during the late‐young stage in 1992 had significantly higher mass than controls, but their mass was not greater than that normally obtained by females not receiving food supplements in other years. We conclude that the results from this experimental study are consistent with the wing‐loading hypothesis, and that House Wrens do not lose mass because of an energy deficit or because they mobilize reserves.