IN TOUCH WITH NATURE

Otago Daily Times, Issue 21244, 27 January 1931, Page 2

IN TOUCH WITH NATURE

SONGS OF DAWN. By J. Drummond, F.L.S., F.Z.S. Although many New Zealanders these days never hear their native birds sing the Song of Dawn, it is, perhaps, the best elfort of the kind in the w'orld. Our native birds, being forest-dwellers, mostly depart from places where fhe ancient trees have given wav to human habitations, but there are places, notably forestclad islands, where the song still is heard in all its beauty. It may delight people now as greatly as it delighted Sir James Banks in Queen Charlotte Sound some 160 years ago. ’ The words in which the botanist expressed his delight have been published before, but are worth publishing again: “We lay about a quarter of a mile from the shore, and in the morning rye were awakened by the singing of the birds. The number was incredible. They seemed to strain their throats in emulation of each other. This wild melody was infinitely superior to any that we have ever heard of the same kind. It seemed to me like small bells, most exquisitely tuned, and perhaps the distance and the water between might be no small advantage to the sound.” In spite of the unrivalled quality of New Zealand’s Song of Dawn, nobody has tried to discover the subtle forces that constrain it. Usually it is attributed to joy at the passing from darkness to light, at the coming of another day. In this case, the songsters feel the same impulse. as led Homer to describe the Lady of the Light in her saffron robe, dispersing her means to every part of the earth, and Aurora, goddess of the morning, rising from her restful bed to bring light to each deathless essence, and use to mortal eyes. Mr H. A. Allard, an American naturalist, who has studied the morning songs in Washington, D.C., finds that birds are highly sensitive to all phases of the morning twilight. For all the different species of birds listened to, the, first morning singing is a highly ordered procedure. At the height of the song season, the order of singing for any particular time is very regular. It seems tq be associated with very definite illumination values attending morning twilight. As to the physiological mechanism of this sensitiveness to phases of the twilight, Mr Allard cannot think of it as anything except a visual impression.

Some species of birds sing all the year round, but the true song season is the mating season, when birds’ physiology undergoes marked changes. Hormones connected with sex may make birds’ nervous organisations highly sensitive to particular conditions of light during the morning twilight, producing Song of unusual volume and quality. This is merely conjecture. It is as far as investigation takes students of the morning choruses. The conclusion of the whole matter is that birds sing on remarkably fine schedules set up by some response of their nervous organisations to the influence of the dawn. Accepting this theory, the bellbird, the tui, the greywarbler, and other New Zealand native birds, at times during the mating season, become highly sensitive to the influences of the coming day. Their visual orgam. sations behave like a very sensitive photometer. apprecating very low intensities of light, on which the songsters base definite form of expression. One of these is the first vocal expression of the dawn, usually distinctive in character and in manner of delivery. In towns, villages, cities, and suburbs in New Zealand some introduced birds, notably the song thrush, the blackbird, the skylark, and the house sparrow, awake early, before sunrise, their notes not only welcoming the dawn, but. also heralding it. Song thrushes are so vociferous at the present time that they sometimes disturb people in their morning sleep. As the season advances the early songg keep pace in time. In England a song thrush at the end of May began to sing about a minute and a-half earlier each day. Listeners could predict almost to a minute when its first notes would be heard. It was noted in America that house sparrows began to chirp 15 minutes before the sun rose, waking correspondingly earlier as the sun rose earlier in the late summer. The first morning songs, according to Mr Allard, do not announce the birds’ first awakening. They stretch themselves out of their proper sleep position and are awaiting alert for the coming dawn long before their first morning song is delivered. Cloudiness at dawn has a definite effect in delaying the first song, with some birds at least. A passing cloud in England has caused birds suddenly to stop their songs, which were resumed as soon as sunshine returned. Another feature mentioned by Mr Allard is that the Song of Dawn always is more distinctively enthusiastic than the evening song. The relations with the intensities of the twilight are not observed so nicely in the evening. Birds often sing longer before sunrise than they do after sunset. This may be accounted for by fatigue at the close of a long, hot, arduous day. Another observer, giving attention to a different aspect of»birds’ songs, finds that some birds usually sing in their own territories, and usually are silent outside of them. In its own territory a male bird has been heard singing even when engaged in combat with another male of the same species. Song, in these instances, is believed to announce a male’s presence, his possession of a territory, his readiness for a mate, and his determination to keep rivals away. On the- other hand, the males of some migratory species, are in full song before the females arrive / in the territories. > Another suggestion is that song sometimes is an end in itself, a recreation and an art, deeply pleasing to the songsters themselves. While song is not restricted to the mating season, it is better, during courtship and immediately before. There seems no doubt that it is used to please the opposite sex and to defy members of the same sex, but that is not its only purpose. The Song of Dawn, so loud and joyous synchronising so regularly with time and circumstances, is a particular expression of emotion, differing as much from ordinary song as, amongst people, the chorus in an oratorio differs from an ordinary solo. „ More speculative ancl less convincing in view of lack of definite knowledge is Mr Allard's suggestion that the sun and the light, which undoubtedly govern the Song of Dawn, must somehow regulate the precisions of the great world-wide migrating movements. With several species of shore birds coming to New Zealand from Siberia -as regularly as clockwork eyerp year this Dominion is as deeply interested in problems of migration as in the reasons for the Song of Dawn, and any fresh contribution to this aspect of birds’ behaviour should be considered. Mr Allard believes that birds may respond to northward and southward movements of the sun in the same way as sunflowers follow the sun in its easterlywesterly course. Guided by analogies, he •suggests that in some w’ay the physiological mechanism of birds synchronise with a celestial phenomenon upon which the swing of the seasons depend. Migration must be regarded as an instinct, so strong that it cannot be resisted. Shore-birds that migrate to New Zealand do not seem to find here anything better than they can find in northern countries, much nearer the places where they were born, and to which they return to lay their eggs and rear their young, places which, to them, must be home, -with all that the word implies. The nature of the instinct that brings them to New Zealand and takes them back again is unknown. It certainly is an inherited instinct. After all. the best explanation seems to be one put forward by Captain E. H. Hutton, pf Christchurch, some 40 years ago. It seemed to him that the migrants follow old land lines, which once were quite clear, but have disappeared. And to this theory, migration began when lands now separated were continguous, or nearly so. Some of the lands gradually sank; but force of habit, handed down from generation to generation, probably maintained the migration until it became an instinct. The changes would be too slight to be perceptible during the life of each bird and only after many years had passed would all the migrants find that they were flying over a trackless ocean.