Experimentally increasing perceived competition for nests reduces female reproductive performance and extra-pair offspring

Activiteit: Academic presentationAcademic


Females often accrue fitness benefits through competition. However, substantial costs can be associated with aggressive behavior in females, and some of these costs are sex-specific maternal effects. Because offspring condition is tightly linked to maternal investment – from development through dependency, a female’s allocation to aggression during the breeding season is expected to affect its fitness. We investigated the costs associated with increased female aggression in the blue tit (Cyanistes caeruleus). To do this, we created an experimental treatment where we elicited female aggression by repeatedly presenting stuffed female taxidermic models on top of nest boxes (one at a time). We additionally ran a control treatment by placing empty cages on top of nest boxes. All simulated territorial intrusions occurred after nest construction and defense had begun, but before eggs were laid. We measured whether females that were forced to increase defense in nests shifted energy and resources away from producing multiple high-quality offspring. We found that females with augmented aggression suffered reduced reproductive performance, laying at a later lay date, and that these females produced offspring that showed less begging vigor compared to offspring from control females. We also found that females with augmented aggression had fewer extra-pair copulations (EPCs), which may have arisen for multiple reasons, including that these females may have spent less time seeking EPCs, or because these females may have become so aggressive that they no longer allowed courting males to approach. These results indicate that costs associated with increased female aggression can occur across the breeding cycle, and that there is a substantial cross-generational reproductive cost when females experience multiple aggressive encounters.
Evenementstitel137th American Ornithological Society Annual Meeting: Birds on the Edge - Dynamic Boundaries
LocatieAnchorage, United States, AlaskaToon op kaart
Mate van erkenningInternational