Males matter: The occurrence and consequences of male incubation in starlings (Sturnus vulgaris)

摘要

The extent to which male parental care increases offspring survival is an important factor shaping avian breeding systems. However, the consequences of male assistance with incubation and the circumstances under which males incubate are poorly understood. We studied a starling population in which male participation in incubation was variable. Incubation periods were shorter, while hatching success and hatchling mass were greater in nests where males assisted females with incubation. These effects did not appear to arise because males incubated only on high-quality nests or when mated to high-quality females. Instead, we suggest that male assistance improved incubation performance by directly improving the conditions experienced by developing embryos. Although females incubated less when males assisted, the male's contribution increased total nest attendance. Males maintained clutches at marginally lower equilibrium temperatures than females but rewarmed cool clutches more rapidly. Clutches consequently spent more time at temperatures likely to facilitate embryonic development. The improved incubation performance resulted in improved breeding success in nests where males assisted with incubation. Male incubation was associated with social monogamy, but many males mated polygynously and did not incubate. Males that incubated had nests that insulated poorly and were initiated relatively late within colonies. Male participation in incubation may therefore decline with a male's ability to provide a high-quality nest and attract multiple females. However, by destroying secondary females' nests, primary females may have been able to increase their chance of receiving male assistance with incubation.