Ardea
Official journal of the Netherlands Ornithologists' Union

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Jones G. (1987) Parental foraging ecology and feeding behaviour during nestling rearing in the Swallow. ARDEA 75 (2): 169-174
The foraging ecology of adult Swallows Hirundo rustica was studied during nestling rearing in a study using precision electronic balances. Load mass delivered to the chicks increased as the brood aged, attaining an asymptotic mass from day 8 onwards, for both sexes. Males delivered significantly smaller loads than females, despite being significantly larger on average in this study. There was no obvious trend for load mass to increase with male age for two males studied over 2-3 years. Load mass was positively correlated with keel-length in females, and was negatively correlated with season. Load mass was not significantly correlated with either brood-size or adult body mass. Food delivery rates over days 8-16 of nestling rearing increased linearly with brood-size, and the slope of the linear relationship was 0.97. Feeding rate, as well as load mass, increased over the rearing period, though continued to increase until the middle of nestling rearing. Self-feeding by parents was implicated on at least 42% of round trips, as determined from mass changes of the parents. Mass gains and mass changes (gains and losses) were positively correlated with time of round trip, while load mass reached an asymptote after about four minutes. Hence it seems likely that for foraging trips longer than about four minutes, food collected for the brood remained constant, and increasing amounts of self-feeding occurred.


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