Destination by Instinct

Destination by Instinct

Some bird migrations are true wonders of nature; that of the young bronze cuckoo of the southwestern Pacific is a baffling accomplishment. Like many species of cuckoos, it is a parasitic breeder. The mother, in New Zealand at nesting time, lays her eggs in another bird's nest and promptly forgets about them. Her most responsible act of parenting is to select a nonmigratory bird, such as the flycatcher, to be the foster parent to her young. As additional insurance of their well—being she often dumps some of the foster parent's eggs overboard to make room for her brood.

Then the bronze cuckoo spreads her wings and heads for the Solomon Islands. Meanwhile the foster parents don't seem to observe the difference in the cuckoo eggs. They incubate the foreign eggs, feed the fledglings, and eventually teach them how to fly.

When the young cuckoo is fully mature, it leaves the nest of its birth and sets out on a journey that carries it 1,200 miles across the sea to Australia. There it rests briefly and then continues its flight. It will then cross another 1,000 miles of open sea to the Solomon Islands. Here it will join flocks of cuckoos that had left New Zealand many months before it had even hatched from its egg. Somewhere among the adult birds in the flock may be the cuckoo's natural mother.

Most amazingly the young cuckoo is able to make a completely unguided flight across over 2,000 miles of open sea. Both the flight path and the destination could be reckoned only by instinct. After that, finding its own flock must be child's play.

Experts in bird behavior do not regard the penguin as a creature of high intellect, and this opinion is well founded. If it were taken out of its natural environment, the penguin would starve to death unless force—fed or hand—fed for a period of time. It would be unable to locate food in a fish market! Being preprogrammed, the penguin does not normally face situations in which logical reasoning is necessary.

As a powerful redeeming feature the penguin has an unshakable homing instinct. Obviously, then, penguin behavior is based on instinct rather than a rudimentary capacity to reason. This would account for its ability to navigate unerringly over vast reaches of open ocean, devoid of any landmarks and quite often fogbound.

As an experiment, early in 1959 scientists captured five adult Adelie penguins near Wilkes Station in the Antarctic. The captives were banded with sensitive tracking devices and flown to McMurdo Sound, over 1,200 miles away. Here they were released and tracked carefully to see if they could make it back to their home ground. The following spring the scientists returned to the Wilkes Station rookery as the penguin population assembled for mating. The former captives waddled ashore and asserted claims to the very nesting sites from which they had been forcibly removed — ten months previously.

From the book: 
Our Fascinating Earth