Friday, October 19, 2012

EXTENDED PARENTAL CARE IN BIRDS


You may be surprised to see obviously immature (brown) gulls at the waterside at this time of year vigorously begging from some nearby adult. You can recognize begging by the bird's throwing its head back and giving loud, high-pitched calls. You may be even more surprised to know that the adult isn't necessarily the parent of that young bird. You may not be surprised to see that the adult ignores the young or chases it away if it remains persistent.

This begging behavior continues into the winter and even to the next spring in some Glaucous-winged and Western Gulls and their hybrids. After all, they have begged for food from their parents for several months, and the behavior is hard to turn off—especially if they are hungry!

Extended parental care after the young have left the nest area is rather rare in birds and seems to be restricted mostly to fish-eaters. It is not easy to catch fish—no bird has evolved a rod, reel, hook and line for the job—so a young bird just starting out to learn how to do this may have a difficult time of it. So although we see these gulls trying to get a little extra parental care, they don't usually get it.

However, young of some other types of birds are successful beggars well after the breeding season. Several species of crested terns have extraordinarily long dependence on their parents after fledging. Juvenile Elegant Terns fly around with their parents for up to six months or more, beg from them, and are fed.

Juvenile frigatebirds may return to their nesting colony for as long as a year after leaving the nest, to be fed by one or both of their parents. Frigatebirds forage by capturing squids and flying fishes at the sea surface, and they have to be very effective at scooping one of these fast-swimming fish from the water. Thus it takes a long time for the young birds to be effective foragers.

Tropicbirds also feed in the open ocean and on the same types of fishes and squids as frigatebirds, although they plunge into the water at high speed to capture them rather than picking them up with a long bill. Interestingly, tropicbird parents do not feed the young postfledging. Perhaps they should, as frigatebirds are thought to have low juvenile mortality for a seabird, presumably because of the extra help they get from their parents.

Dennis Paulson

1 comment:

Michael said...

What about other types of birds and not just sea birds? I don't know much about birds, but I remember watching all those childhood TV shows where the mamma bird comes back to the nest to feed her offspring.