SYMBIOSIS—ANIMALS LIVING IN MIXED HOUSEHOLDS [Ref]
Symbiosis, a term from the Greek, is what the biologist uses for the living together of two dissimilar organisms. In a broad sense it includes such diverse relations as the lice living on man and rats in his house, the union of an alga and a fungus to form a lichen, and the cross-pollination of flowers by hummingbirds.
The story of the burrowing owls of our Western plains living in amity with prairie dogs and rattlesnakes as one happy family comes to mind as an example. But "foolish nonsense" is how the noted biographer of North American birds, A. C. Bent, characterizes such stories. He then goes on to quote evidence as to what actually happens, and one can see how the story originated. The prairie dogs, which are really plump, dumpy, ground squirrels and not dogs at all, dig their burrows close to each other on the prairie in colonies which have come to be called prairie-dog towns, or dog towns or simply "towns." Burrowing owls also take up their residence in these towns, probably because they find burrows ready made and do not have to dig their own as they are quite able to do.
MODERATELY PREDATORY The owls may make an occasional meal of a young prairie dog, and a prairie dog may perhaps dine occasionally on owl eggs, but on the whole owls and dogs get along on terms of easy familiarity. Sometimes when alarmed, both may scuttle into the same burrow for safety, but each has its own burrow. With the rattlesnake it is different. The rattlesnake may live in burrows in the dog town, but when it is hungry it eats owl or dog as occasion offers. While the picture of a happy family of owl, dog, and snake is a myth, the symbiosis of owl and dog, at least in the same colony, is striking.
In Africa there is a tiny falcon only about eight inches long which is called a pygmy falcon because of its small size. When Dr. Friedmann was studying the social weavers in South Africa, birds which nest in large colonies under a common roof they make in a savanna tree, he found these falcons occupying nest chambers in thriving weaver colonies. There was no friction between the weaverbirds and the falcons, and they were sometimes seen to sit side by side. When Friedmann collected three of these falcons he found bird remains in their stomachs but they were not remains of the social weavers. Apparently the falcons were feeding largely on small birds, but they did not molest the weaverbirds which had made the nests the falcons were using.
PARROT-DUCK-OPOSSUM MÉNAGE We occasionally find a mallard nesting in a tree, on an old crow or hawk nest, and there are ducks like the wood duck and the golden-eye, which usually nest in holes in trees, but a South American duck called the tree teal habitually nests in a parrot's nest. The parrots, called monk parakeets, make their nests in compact colonies in the branches of trees, so close together that they form a single mass. The tree teal's usual manner of nesting is to lay its eggs in one of the chambers in this apartment-house colony. At first the eggs are laid on the rough twig floor of the nest, but as the eggs increase in number a lining of down, plucked from the breast of the bird, is added until it may even extend out the entrance of the nest. Apparently parrot and duck both get along amicably in their pendant treetop cradles. An opossum sometimes also finds these parrot nests to its liking, though one wonders if it may not have a meal of young parrot or duck in mind. But be that as it may, in different chambers of a single communal nest of these parrots, parrots, a duck, and an opossum have been found.
On islets off the New Zealand coast lives a rather large-sized lizard called Sphenodon. It's rather well known by name, at least, for it is one of those relics of a formerly more widespread group which are called living fossils. It is also noted for its remarkable development of a pineal eye, the remnant of an important sense organ in ancestral forms, and formerly an organ some philosophers supposed to be the seat of the soul. But here we are interested in the fact that petrels swarm to these same islands to dig their burrows and lay their eggs in them, and it is in these same burrows that Sphenodon spends its daylight hours. Apparently the insect-eating Sphenodon and the oceanic-feeding petrels share the burrows amicably, adding still another example of a rather long list of dissimilar organisms whose lives are associated.
BIRD APARTMENT HOUSES [Ref]
