On a midsummer day a flock of 40 mergansers swims along the edge of a saltchuck, an intertidal pond. They favor the shallows and the margins of the waterweeds - there are hungry eagles watching and the vegetation provides an escape to cover. This is no ordinary flock; it's comprised almost entirely of young of the year, big merganser ducklings banded together in a crèche. There are a few adult females mixed in, but there are too many ducklings for these to be their babies. The adults are essentially babysitters.
A variety of birds will form crèches, aggregations of young watched over by a few adults. Some penguins do this, Canada geese, and some terns. Flamingos also do this, and parents will return to the crèche to feed their young. It was once thought that adults indiscriminately fed the young, but observations showed adult flamingos find and feed their own young. Terns also recognize their own young by their voices and calls.
Birds aren't the only animals to form crèches. Spectacled caiman, a South American crocodile, raise their young in crèches, one female taking care of her own as well as other mother's offspring. Lions also form crèches, and females within a pride will provide mutual protection and even nurse each others' cubs.
Merganser chicks, like other ducklings, are precocial and don't need a lot of care - they hatch out capable of swimming and feeding themselves. A few adults keep watch for predators and help keep the crèche together. In a few months, these young ducks will be adult size and ready for their first winter.