For the Birds Radio Program: Baby Bird Biology, Part II
Laura talks about unusual baby birds.
(Recording of a American Robin)
Yesterday I talked about the two kinds of baby birds. Actually there are gradations of both precocial and altricial young. The most precocial of all birds are the megapodes, that is, the brush turkeys and Malee-Fowl of Australia, and one species of waterfowl, the Black-headed Duck of southern South America. In these birds the young are completely independent and able to care for themselves from the moment they hatch. The Australian megapodes lay their eggs in a mound of sand, reptile like, and their parental responsibilities are limited to occasionally stirring the sand to keep it loose enough for the babies to dig their way out of the mound when they hatch. The South American Black-headed Duck makes no nest at all. The female lays her eggs in the nests of a wide variety of other species, especially grebes. These foster mothers incubate the duck egg along with their own, but as soon as the Black-headed Ducklings hatch, they go off on their own, and neither the biological parents nor the parents that hatched them give them any further assistance.
In many precocial birds, like our own ducks, shorebirds, and the New Zealand Kiwi, the young are led to feeding areas by their mother, but once there, feed themselves. When only three days old, a Lesser Scaup, or bluebill, is capable of diving, capturing a minnow, and returning to the water’s surface in five seconds flat. Ruddy Ducklings raised in an incubator and set loose in a marsh when only one or two days old raised themselves successfully without any adult care.
But some precocial young are given more help. Domestic chicks receive a great deal of assistance in feeding from their mother, who scratches vigorously to unearth an edible morsel, and then may pick it up, soften it in her bill, and then lay it down and point her bill at it until one of the chicks swallows it. Adult snipe and oystercatchers have been recorded passing food morsels to their young in their beaks, and it is possible that other sandpiper and plover babies also get some assistance from their parents.
Gulls and terns are hatched with a covering of down, and are quickly capable of leaving the nest when disturbed, but they are directly fed by their parents for about a month before they can learn to fish on their own. These birds are considered subprecocial. It takes baby flamingos three days before they can leave the nest when disturbed, and the young all leave when 8 days old, but they are fed by their parents until they are two or three months old.
Altricial birds are all pretty helpless, but some are capable of more independent activity than others. Baby woodpeckers are completely naked and unable to do anything more than beg at first. Belted Kingfishers, which are born in burrows, are also naked, but if their burrow is dug out from the rear, they will toddle away from the light. Some are considered only semi-altricial, if they are covered with down but cannot leave the nest. In this category are hawks and eagles, which also hatch with their eyes open, and owls, which hatch with their eyes closed. When some of these big babies fall out of the nest, they hop up into tree branches for safety, but baby Great Horned Owls often stay right on the ground, puffing up their feathers and assuming a grotesque posture when frightened.
Yes, baby birds are many and varied.
(Recording of a Great Horned Owl)
This is Laura Erickson, and this program has been “For the Birds.”