If male jacana could sing the blues, these birds would have plenty to wail about. While the typical female cavorts wide and far, her loyal partner stays at home and cares for nestlings that may not be his own. But some consolation is reported in today's Royal Society of London Series B: If it weren't for the cuckolded dad's willingness to care for the young of others, the researchers found, the species would disappear.
Wattled jacanas are black, quail-sized birds with puffy red faces and extremely long toes that wade through the marshes and slow-flowing rivers of Central and South America. But it's their less than orthodox family life that intrigues scientists. The female keeps a harem of up to four males, copulating, on average, 65 times per breeding season--far more than is necessary for fertilization--before laying a clutch of four eggs. "The jacana is the ultimate in female liberation," says Cornell University ornithologist Stephen Emlen. "A male jacana sits on the nest, watching the mother of the chicks he will raise, while she continues to mate with other males nearby."
Curious as to whether the males might benefit from the situation by passing on more of their own genes, Emlen and his colleagues observed the mating and egg-laying habits of the jacanas on the Chagres River in Panama for 6 years. They tested a total 465 females, males, and chicks for parental lineage. On average, 40% of the males had reared chicks they hadn't sired. For males who had devoted themselves to particularly promiscuous females, some 70% had been cuckolded. And none of the poor guys passed on more of their genes.
The finding counters the common assumption that males only help rear their young if they're sure of paternity, says Michael Webster, an ornithologist at the University of Buffalo in New York. Since jacana females have completely lost the instinct to brood, the males are the only hope for chicks. "The males are trapped in care-giving roles," says Webster.