The evolution of greater male than female parental care remains poorly understood. In birds it is thought to be related to precocial chicks and small clutch size. This review shows, however, that such role reversal has also evolved in a family with altricial young and relatively large clutch size: coucals (Centropodidae, Cuculifonnes). Malcs perform most nest building, incubation, and feeding of young. As predicted by sexual selection theory, coucals have also reversed sexual size dimorphism, females being larger than males in all 12 spc-cies for which size data are available. Most coucals that have been studied are monogamous, but the black coucal Ohlropus g d i i appears to be polyandrous, and males perform almost all parental care, whereas females show more active advertisement behaciour. In this speries, females are about 50% heavier than males. Polyandry in the black coucal seems to be associated with a shift to a habitat with seasonally rich food resources. Difficulties for female coucals of gathering enough resources for producing several clutches of relatively large eggs may favour mainly male parental care. Female sexual competition and resonrce storage, and male foraging economy, may explain why females are larger. Additional field studies are needed to test these hypotheses; the coucals are of great interest to sexual selection and mating systems theory.
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