Parenting chores cut into how much these bird dads fool around

The extreme dads of the bird world do all the work raising chicks while females fight intruders. The result: Male black coucals don’t sleep around as much when busy parenting.

On occasion, a male black coucal (Centropus grillii) slips over to another male’s nest to sire a chick. The demands of incubating eggs, however, reduce a male’s excursions about 17 percent, on average, compared with male birds that didn’t have chicks. And during the frantic first week of parenting after eggs hatch, those philandering excursions drop by almost 50 percent, researchers report April 10 in the Proceedings of the Royal Society B.

That’s when male coucals, native to sub-Saharan Africa, spend much of their days catching grasshoppers, frogs and other critters to feed chicks too frail to leave their woven grass nests, says behavioral ecologist Wolfgang Goymann at the Max Planck Institute for Ornithology in Seewiesen, Germany. Even when chicks can leave the nest, they’ll need at least two more weeks of dad’s care.

These coucals are among the few bird species in which females, rather than males, stake out territories and defend them from other females. The females are bigger than the males and warn interlopers with “hoot, hoot” exchanges, which deepen in pitch if antagonists get closer. If hooting fails, one female will fly at the other bird to fight.

“You see just the grass moving, and you hear a grumbling,” Goymann says. Sometimes he spots females “with huge wounds on their heads.”

A female’s territory has up to five males nesting in it. She builds the basics of a nest and lays eggs with each male in her realm. Unlike other nestlings with dad-only care, these chicks hatch very early in development. They don’t even have enough fluff for warmth, and dad needs to snuggle them for about a week before they can leave the nest.

Even when dads are busiest, they don’t stop slipping off to nests of other males both inside their mate’s territory and outside. DNA testing revealed that about half of the male coucals that Goymann studied in southwest Tanzania’s wetlands over 12 years were caring for at least one chick sired by another male, the researchers found.

Males have a strong urge to feed youngsters, even if they’re from other nests, Goymann says. When he traced bird trackers worn by three chicks and their dad to the innards of a venomous puff adder, he assumed that the lone surviving chick was doomed. However, a neighboring male tending chicks of his own stepped in and fed the survivor.

Philandering aside, the black coucals “are devoted dads,” Goymann says.