© Marcel Burkhardt
Grüebler, M. U. & B. Naef - Daenzer (2010)
Survival beneﬁts of post-ﬂedging care: experimental approach to a critical part of avian reproductive strategies.
J. Anim. Ecol. 79: 334–341
1. Caring for offspring beyond leaving the nest is an important but under-studied part of avian life histories. Theory predicts that prolonged post-ﬂedging parental care should yield ﬁtness beneﬁts such as increased ﬂedgling survival. Post-ﬂedging care is also costly in terms of time and energy available for subsequent reproduction, moult or migration. So far, direct measurements of the ﬁtness effects of the duration of post-ﬂedging parental care are lacking.
2. In a partial cross-fostering experiment, barn swallow (Hirundo rustica) chicks were exchanged among broods close to ﬂedging. Thereby, we separated the effects of post-ﬂedging care from those of pre-ﬂedging origin on juvenile survival.
3. Prolonging post-ﬂedging care substantially increased juvenile survival up to 3 weeks post-ﬂedging. Juvenile mortality was maximal in the days following the termination of parental care, and prolonging care delayed and reduced this peak mortality. Survival of ﬂedglings experiencing 6 days of care was ɸ = 0.227, whereas ﬂedglings experiencing 14 days of care showed a survival of ɸ = 0.571.
4. Offspring from pairs providing short care showed lower post-ﬂedging survival than did off-spring from pairs providing long care, irrespective of the actual duration of care experienced. This gives evidence for an additional survival effect of pre-ﬂedging factors associated with the parental duration of care.
5. The results suggest that differential survival in relation to post-ﬂedging parental care is a major ﬁtness component. This relationship has profound effects on there productive trade-offs underlying the evolution of avian life histories.
Keywords: Avian life history, juvenile survival, parental care, post-ﬂedging period, reproductive effort