IN TOUCH WITH NATURE

Otago Witness, Issue 3595, 6 February 1923, Page 6

IN TOUCH WITH NATURE

BIRDS IN A GARDEN.

By

J. DRUMMOND, F.L.S., F.Z.S.

“I don’t know if you are aware that the notes of the song-thrush differ with different members of the species,” Mr J. Joyce wrote from Bligh’s road, Papanui, near Christchurch, on January 3. “There are several song-thrushes in my garden, and I have made it a study to become familiar with the notes of the best songster and compare them with the notes of others. I find that the others do not use the notes I am accustomed to hear from my favourite. I often was 'curious to learn if all songthrushes used the same notes: I am satisfied that each individual has his own notes'. Song-thrushes, which are very plentiful in my garden, begin to sing regularly every morning about a quarter past three. One begins, then another and others follow, until some six or seven provide the melody. They continue until there is sufficient light for them to pick up their breakfast, generally of snails. They hammer the shells on bricks and stones, and get at the flesh. When they have retired after their matins, blackbirds appear with their soft, melodious notes. They are more timid than the song thrushes. “When the blackbirds have finished, we hear a flock of little white-eyes, which keep Up their lively songs for almost half an an hour. Their notes, absolutely incessant, and resembling the tinkling of many glasses, continue until daylight is quite in evidence. We then have an hour’s unpleasant chirp ing and chattering from scores of sparrows, and all the chance of a snooze has gone Until they have reached the end of their programme.’’ Mr Joyce seldom hears the

skylark now. He believes that it shares poisoned breakfasts prepared for the sparrow, a custom that is reducing its numbers. Fan tails are not as plentiful as they were ; he never hears parrakeets chattering in the bushes these days; and the black and white tomtit, which reminded him of the Old Country’s Robin Redbreast, has. deserted his garden. It covers three acres. In it there are many shelter trees, including ivy-twined cabbage trees, which are used by birds at night. A fragment of fossil found some wears ago in a road cutting at Napier, and sent by Mr H. G. Stillman, Palmerston North, is the remains of a member of a race whose dominance in Mesozoic Seas makes its extinction all over the world near the end of the Cretaceous Period a palaeontological puzzle. The ammonites were cephalopods, which lived in spiral chambered shells. Unscientific reasoning saw- in the fossil shells a resemblance to the rams' horns of .Jupiter Ammon, and “ammonites,” the legendary title given to the shells, w 7 as appropriated by zoology for the creatures that made them. No group of creatures, living or extinct, perhaps, offers a better object lesson for the stduent of evolution. From early Devonian times, in the Palaeozoic Era, until their career culminated in the Upper iriassic Period, w-hen there might have been 10,000 different species of them in the world, they evolved w-ith almost uninterrupted progression. They then began to decline, and not a single individual, apparently, crossed the fatal border between the Mesozoic Era and the Cainozoic Era. They seem to have faced a crisis early in the Mesozoic Era, when their numbers were decreased. Surviving that setback, they developed amazingly until the decline that led to their parsing completely off the stage.

The most surprising part of their history shows that, so far from clinging conservatively to old-fashioned ideas, they mostly were rapidly-changing creatures. The exceptions to this rule are supplied by two genera, which changed little from the end of the Triassic Period through the Jurassic to the Cretaceous. The decline of the race synchronises with the increase of predaceous sharks, which, although not common until the Cretaceous. Period, appeared with sharppointed teeth in their jaws in the Jurassic Period. The ammonites, swimming slowly, and encumbering the ancient seas with their numbers, their fragile shells offering no protection, may have been extirpated by Jurassic and Cretaceous sharks. Over-specialisa tion, racial decay, and climatic changes also are given as causes of the fate that befell those distinguished relatives of the lovely pearly nautilus of modern seas, hut the evidence is so slight that theorising merely is toying with possibilities. They probably were ancestors of Spirula, whose chambered shells, shaped like tiny rams’ horns, are found scattered in thousands on New Zealand shores, and on the shores of a few- other countries, mainly in the tropics. In spite of the abundance of Spirula shells, only a few of the creatures that make and occupy them have beer found. One w-os found in New Zealand many years ago. Another was taken by the H.M.S. Challenger in a deep-sea trawl in between 300 and 400 fathoms of water near the Moluccas. They seem to be strictly deep-sea shellfish. The structure of Spirula’s coiled shell distinguishes it from all other living cephalapods, but establishes a connection with the ancient ammonites. No fossil Spirula has been found The shell is completely white and pearly inside, loosely coiled, and divided into chambers by partitions like the shell of the nautilus. Each Spirula, in its extreme youth, seems to live in its tiny chambered

shell, hut it soon outgrows the shell, which it then carries at the end of its body a 3 ammonites, probably, carried their shells. The fact that Spirula shells are cast up by the sea is accounted for by the conjecture that when a shell is freed by ics owner, the chambers cause it to float, and in time it is washed ashore. Mr R. 11. D. Stidolph, Makaroa road, Masterton, states that- the practice of removing eggs after a nest lias been inspected by strangers is not confined to the skylark. On December 30, near the shore of Onoke Lake. Palliser Bay, he flushed a pipit, commonly known as a ground lark, from its nest at the foot of a Californian thistle. The nest contained four eggs. Oil January 2, when he examined the nest again, it was empty. It was improbable that the eggs had been taken by any person, and there were no signs that they had been destroyed by natural enemies. Pot-holes formed by the action of wares near Plimmerton, Porirua Harbour, west Coast of Wellington Province, have been noted by Mr A. L. Adkin, of Levin. A shore platform there is composed of comparatively soft weathered rocks and lines of weakness in the rocks were hollowed out by waves in the shape of grooves. Travelling boulders or cobbles of very hard grit rock, known to geologists as greywacke—pronounced “greywack-ee”—were propelled landwards until they became wedged in fissures or met with obstructions that prevented their further progress. In the latter case their forward motion became a circular one, causing pot-holes. Each pot hole, unless affected by one of its walls breaking away, is enlarged. The largest one Mr Adkin measured was 3ft 6in in diameter and 2ft deep. The combination of factors and conditions necessary for the formation of wave-made pot-holes is particularly in evidence in Porirua Harfour.

Mr Adkin states that he has not seen any reference to the formation of pot-holes by the acjion of the waves in any part of the world, and that, although the phenomena may have been noted previously, it probably is very rare. Pot-holes are not unusual in hard rocks in New Zealand riveroeds. they are made by boulders or large pebbles, swirled around by eddies for a long time. The first boulders or pebbles may be worn away by the process, but others take their place, and each river pot-hole usually contains several rounded stones. A diversion of the Wairua River, North Auckland, has exposed a pot-hole in the rock bed.