|
cide even when their surroundings duplicated those found in their native habitat? It seemed the birds were programmed to kill their offspring. Obviously, this could not be an instinctive behavior, or this species of bird would have been wiped out in the first generation. But it turned out to be related to an instinctive behavior.
Birds do many things on the basis of instinct. We are constantly amazed by some of the incredibly complex behavior patterns of birds. Mating dances and fancy feather displays, nest building, egg sitting and regurgitation to feed the young are all programmed through genetic transmission. This automatic programming almost always helps the species to survive.
So why then did these rare birds dump their newborns? The answer lies in a species adaptation to maintain hygiene and to avoid disease. It is obvious that a dead chick left in the nest will gather flies and disease. We would not question a parent bird discarding a dead chick. The key to the problem can be found by comparing the behavior of the young birds at the zoo with their cousins in the wild.
In their natural habitat, adult birds stake out territory ~ around their nest, which they protect from incursion by other birds of the same species. This ensures them of a food supply. Without competition or predators, the number of birds increases until the available territory for bird, or bird pair, shrinks and the food supply limited. The task of mustering up enough bugs for the family takes all day, and the supply is just enough to survive.
Under these conditions, the chicks are in a state of constant hunger, which they indicate with upturned heads and open beaks. The adult birds are instinctively programmed to regurgitate food into these squawking gullets. Unfortunately for their zoo-born birds, the food supply set up was over abundant. The parents had so much food, they were able to satisfy the young chicks' appetite completely. The chicks took long naps. The naps lasted so long instinctive drive to rid the nest of dead chicks took over, and out they went. To solve this problem the zookeepers had only to limit the food supply to these birds. This kept the chicks hungry, active and alive.
|
|
