An experimental study of mate guarding and paternity in house wrens

Males are thought to have evolved paternity assurance mechanisms in response to the potential for multiple mating by females, but the effectiveness of these mechanisms can vary. Mate guarding is the most common paternity assurance mechanism found in birds, but there are few studies that examine its effectiveness in protecting paternity. We examined the effectiveness of mate guarding in house wrens, Troglodytes aedon, by experimentally preventing males from guarding via a short-term detention during the femaleʹs fertile period. Compared with control males, experimental males had significantly lower paternity in their broods and their mates made more frequent and longer extraterritorial forays. We also found that the increased proportion of extrapair young in experimental broods was associated with: (1) longer intrusions by extrapair males onto the territory of the detained male, and (2) shorter extraterritorial forays by the resident female. Although experimental males were more likely to be cuckolded, they did not reduce their parental care to nestlings. These results support the hypothesis that male mate guarding can effectively reduce the risk of cuckoldry.