NATURE NOTES.

New Zealand Herald, Volume LXIV, Issue 19780, 29 October 1927, Page 1 (Supplement)

NATURE NOTES.

BIROS AND TERRITORIES.

BY J. DEUMMOND, F.L.S., F.Z.B.

The huia is an illustration, perhaps on© of the best in the world, of a species of bird occupying a restricted area and seldom leaving it. The huia has been reported outside of the Ruahine, Tararua, and Rimutaka Ranges, but not often. • In New Zealand there are many cases, also, of pairs cf birds and individuals occupying restricted areas, and of the males, at least, resenting the intrusion of members of their own species and their own sex into their domains. This sense of territorial ownership, which leads to bitter duels between male tomtits and between male wood-robins, has been noted by New Zealand observers, but has not been studied by them. In the Old Country it lias opened up a fresh line of research. Seasons of paiient watching in English fields and woods- has led to the conclusion that almost all birds there, when the mating season arrives, stake out territories for themselves, and that these territories, in most instances, are the pivot on which the sexual lives of the birds turn.

The subject has given Professor Julian Huxiey, London, materia! for an interesting chapter in his new book, "Essays in Popular Science." He finds that usually it is a male who annexes the territory. When this step is taken, the male spends all his time, or most of it, m a restricted area, defending it from all other males of the same species; but the annexation takes place long before the male seems to manifest any interest in the females. The annexation is marked in forms that belong to widely different groups. Among the English warblers, the males arrive from their winter quarters a week or more before the females. They occupy a definite area, fight for possession of it, if necessary, and spend almost all theii time singing. The strangest part of the affair is that those songs usually are more brilliant than the songs sung after the females have arrived. At first, when the females arrive, there is no courtship in the ordinary sense. On the contrary the males seem to be almost oblivious of their future mates. Courtship does not begin until the territories have been staked out and occupied. The males then assume extravagant attitudes and perform actions obviously directed at the females.

The same procedure has been observed in England among yellow hammers. These golden-headed birds were introduced into New Zealand years ago. They have spread all over the Dominion. In the English winter they collect in flocks in the stubbles. When spring begins the males detach themselves from a flock for a short while each day and go to a particular stretch of hedgerow. They there spend most of their time on a particular tree, singing. As the season advances the time they spend with the flock gradually decreases and the time they spend in the territory gradually increases, their activities in singing also increasing.

Professor Kuxley believes that territory, in some form, plays a part in the lives of all birds. The Kingfishers of the Old Country divide their rivers into sections. The crested grebes—the same species as the crested grebes that ornament some New Zealand lakes, or close allies of them—make the open water a, common fishing-ground, and merely delimit territories around their nests in fringing beds of reeds. In these facts, Professor Huxley sees a principle of great importance when people try to understand the lives of birds. He assures people in all parts of the world that, in the observation of bird-life, valuable results await those who have the patience to collect them.

There is in New Zealand a little tawny insect, Drosophila. Experiments with it in other countries show that it lives more intensely at higher temperatures than at lower ones, but, at the higher tempera tures, it has a shorter life. From time of hatching to time of death, at lOdeg. Centigrade it lived 177 days, almost six months; at 20deg. it lived 54 days; at 30deg only 21 days. A hatch of frogs' eggs was divided into four sections. At the end of three days, the eggs in one hatch, kept at 24deg., were tadpoles, ready to hatch; two hatches, one kept at 15deg. and the other at 20deg., had not advanced to that stage; the eggs in the remaining hatch, kept at ll.Sdeg., had not completed their primary ground-plan, and still were simple spheres. Quicker development again went hand-in-hand with higher temperature. All the embryos had lived the same number of days, hours, and minutes, but each hatch had accomplished the different portion of the life-cycle; each had gone a different distance along the road that leads to old age and death.

The facts are simple; but they raise a profound problem associated with control of the life-cycle. The difficulty Professor Huxley has encountered is to apply the principle of increased growth with increased temperature to human beings. It cannot be done, because, as far as temperature goes, human beings are self-regu-lating. They have contrived an internal temperature environment for themselves. In very wide limits, this ;s independent of changes of temperature that take place in the world outside. Yet Professor Huxley goes as far as to state that men of science are beginning to gain an insight into the machinery cn which the control of the human life-cycle, from birth to death, depends He is convinced that the twentieth century will see a revolution, brought about by mastery over organic nature. It will be greater than the revolution that gave mastery over inor ganic nature, because "the stuff that will be controlled is the basis of our thoughts and emotions and very existence." But the lesson learnt by this biologist is that mankind's future depends on the quality of the individuals that make up society, and on the way in which society is organised—its laws" its constitution, its custons, its religion, its education, and its organised traciition. These essays there are twentv of them—help people to think scientifically. They help people to thinkabout themselves, and about the intimate facts of their lives, and they show that biology is the servant of man.

A dark insect, about half an inch long, found on the surface of a freshwater pond at Balclutha, by Mr. A. .T. Middleton, is a whirligig beetle. New Zcalsnd has only one species of whirligig beetle, as far as is known at present, but in Australia twenty-eight species have been identified. The whirligigs belong to the family Gyrinidae, which,' like their popular title, has been earned by their strange, intricate whirligig "stunts" on the surface of the water. Some entomologists see in these swimming performances graceful circles and curves, and delight to watch the ease, precision, and speed of the complicated movements without ever a collision, when manv beetles take part in them. Although 'the beetles cannot walk on land, they flv well, and always by night. When alarmed at play, they plunge below the surface, each carrying down a miniature bubble of air. Hie females lay long slender eggs on water-weeds. In the grub stage, the beetles are active, predatory and voracious and highly modified for their strictly aquatic lives. In the adult stages, they are, in their construction, better adapted for life on the surface of the water than are any other j insects. In addition to being able to dive in order to escape danger, and to take beneath the surface a small supply of air, their hind legs are beautifully fashioned paddles. These expand mechanically when moved in a backward direction, and collapse into a very small space as soon as the resistance they meet with is in the opposite direction.