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October 2000
It seems to me that cooperation, not competition, is the underlying principle in nature. When we look at the world without preconceptions, we see evidence of cooperation at all levels of life.
Distributing the demand on food resources is a form of cooperation. In some bird species, males and females feed in different locations in their habitat. Male downy woodpeckers prefer foraging on branches and in the upper canopy. Females forage on the tree trunk. In winter, male hairy woodpeckers forage for food higher in trees than the females.
Breeding pairs of many bird species cooperate in a variety of ways in reproduction. They may both be involved in building the nest, incubating the eggs and feeding the nestlings. The male titmouse feeds the female while she is incubating the eggs. On occasion, birds from the pair's first brood bring food to the young of the second brood. Male and female rose-breasted grosbeaks incubate the eggs and care for the young. If there is a second brood, the female leaves the nestlings in the first nest to build a second nest in the area; and the male is responsible for all care of the young from the first nest.
Some birds, such as red-winged blackbirds, starlings, swallows, and many seabirds, roost communally at night during certain times of the year. Roosting is a period of inactivity for birds, as sleep is for humans. There may be several reasons for communal roosting. Younger birds may roost with older birds because the older birds are more successful in finding food, and are followed by the younger ones when they go foraging. Older birds gain an advantage because they roost in the center of the group, a safer spot less vulnerable to predators. Another reason for communal roosting at night is keeping warm. In winter, small groups of nuthatches huddle together in tree cavities.
With birds, cooperation in dealing with predators may occur in mobbing behavior, a noisy group demonstration. A group of blackbirds may be seen chasing a hawk. Songbirds flutter and call around an owl. The interpretation of this group behavior, because it most often happens on breeding grounds, is that it distracts the predator from an area where there are fledglings. However, black-capped chickadees mob in winter. Because surprise may be important in successful hunting by raptors, mobbing may alert other birds to the danger. Mobbing may also be educational. Research has shown that birds learn from one another which predators to mob, and so young birds learn who is a threat.
Mixed-species flocking may function as a strategy against predators, where some species in the flock are more far-sighted than others. In winter, chickadees and titmice serve as sentinels to warn the downy woodpeckers in their flock. The chickadees and titmice may benefit by learning locations of food sources by observing the woodpeckers.
Then there is cooperation in indirect ways. Hoarding food to survive through periods of limited food resources, like winter, is a strategy practiced by some animals. Oak trees are planted and forests spread when blue jays and squirrels store acorns but don't retrieve them. The northern flying squirrel has a diet of lichens and subterranean fungi. When it feeds, fungal spores and nitrogen-fixing bacteria are released, and these help trees obtain nutrients and water.
There is the essential cooperation between trees and animals. Trees, through transpiration, take carbon dioxide out of the air and release oxygen. Animals, through respiration, take oxygen out of the air and release carbon dioxide. Then there is the ultimate cooperation: the food chain, necessary to the continuation of life on earth.
By Nancy Coverstone (ncstone@umext.maine.edu), University of Maine Extension Educator in Androscoggin and Sagadahoc Counties
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