Stray Feathers From a Bird Man's Desk

by Austin Loomer Rand

Best known of the "gardens" and "animal husbandry" of the lower animals are those of the ants; the aphis kept by the ants for the sake of a sweetish secretion, and the underground fungus garden of the ants. In the vertebrates I know nothing comparable to this, but we do get a number of cases where there is a definite relation between the animals and the growth of vegetation.

It has been said that in the antarctic the nesting colonies of some penguins are detrimental to the vegetation. The constant passing and standing of the birds on the limited areas of soil preclude the growing of vegetation over sufficiently large areas to be an important factor in hindering plant growth. But the reverse is true of the Johnny penguin in the Falklands, where it is sometimes known as the best farmer in the country. The Falkland Islands, off southern South America, are cold, wet, and windy. Sheep raising is one of the main industries. And the Johnny penguin helps to provide better pasture for the sheep. The birds nest in colonies and their droppings help to enrich the land so that the grass grows taller and richer. Rather than using the same area for their breeding colony each year the birds select a new, clean area at the beginning of each breeding season, so that they improve the ground over a larger area.

From the arctic comes another example of a relationship between bird and plant. On the arctic barrens, here and there, are large boulders, erratics left by the glacier that covered the land in times past. And on these boulders, and here only, one finds patches of bright yellow or reddish lichen known to scientists as Xantheria or Xanthoria. Apparently its presence is owed to the fact that these boulders are the lookout places of snowy owls, hawks, and other birds. Their droppings, falling on the rocks, provide the nutrient layer necessary for the growth of the lichens. It is probable that these lichens are transported from place to place by the birds carrying the soredia on their feet. In recognition of the close relationship between these lichens and birds an ecologist has coined the rather formidable term "ornithocoprophilous" to express the relationship.

Also in the arctic are the arctic-fox gardens. The arctic fox often makes its burrows in sandy places, and about the entrance to the burrow accumulate remains of former meals, fox droppings, and suchlike animal debris. This in time enriches the soil and the vegetation there grows taller and more lush than elsewhere on the barrens. This lush vegetation attracts the small, mouselike arctic rodents, the lemmings, that feed on green, succulent vegetation. There is of course one further step in this chain. One of the important foods of the arctic fox is the lemming, which he thus brings to his door by the richer vegetation he unwittingly causes to occur there. A charming arrangement, one of the old naturalists called it.

DROPPING THINGS [Ref]

The story is well known, being recorded by Pliny, of how the poet Aeschylus came to his death through a bird mistaking his bald head for a rock and dropping a turtle on it. The bird was evidently the lammergeier or "lamb vulture," one of the largest and most magnificent of the Old World birds of prey; nearly four feet long. In the Atlas Mountains of North Africa its normal food is turtles, and these it cracks open, so that it can get at the meat, by carrying them up into the air and dropping them on a rock. Now it lives in the Himalayas and in Africa, having been almost if not completely exterminated from Europe because of its alleged predation on sheep. Not only turtles but bones are treated in the same manner, to get at the marrow. Though the habit is well known, it is surprising how difficult it is to find a firsthand description of it. So far I know of only one description written by an eyewitness. And yet, in East Africa recently a stony mountaintop was found littered with broken bones that seemed to be the result of the lammergeier's habit.

GULLS DO IT As I have mentioned, gulls open clams and mussels in this way; and crows, which are among the most intelligent of birds, do it also. They pick up the mussels left exposed by the falling tide, fly up above a hard stretch of beach, a big rock, or a stretch of nearby paved road, and drop the shellfish there. While in general this practice is restricted to a few groups of birds, it is practiced by them in many far parts of the world. The Pacific gull of Australia, widely separated from its near relatives, has the same maneuver for opening shellfish as has our herring gull.

It's hard to understand just how this habit came about. One can imagine that some birds found it out by accident when flying about with a stubborn "nut" they were unable to crack. Or perhaps it was in play they found it. The raven is known to fly about carrying and dropping things in play.

SPARROWS DO IT TOO Often, to find a background if not an explanation of a habit, we look about to see if it's used in some other connection. I've already mentioned the play of some of the crows. Only one other "dropping" habit has come to my attention, and that is a single record for the very common house sparrow. Edmund Jaeger writes that in Nebraska, and again in Riverside, California, he saw house sparrows on gravel roofs, dropping small stones over the edge. The pebbles, or small bits of crushed stone, were carried to the edge of the building by the sparrows, dropped, and as each pebble was dropped the sparrow turned its head, apparently the better to watch or listen to the pebble fall and strike. No obvious utility appeared in these actions. It, too, looked like pastime. Perhaps there was no better reason behind them than that behind small children dropping stones down a well.