Fifth Meeting: 5th August, 1909.
Present: Dr. Charles Chilton in the chair, and over a hundred others.
New Member.—Mr. F. S. Oliver.
Mr. Edgar F. Stead then delivered his lecture on “Bird-life in New Zealand.”
First of all he exhibited a number of skins of birds, including those of the kea, sparrow-hawk, and rifléman. He showed, too, the skin of a curlew stilt, the third he had secured in New Zealand. This bird, he stated, bred in the Yenesei Valley, and came here in the summer. The last specimen he obtained was still in its winter plumage. “Here is a knot,” the speaker continued, exhibiting a specimen with a brilliant breast and other conspicuous markings. “He is in his evening dress, which he wears when he goes courting, and it is quite an elaborate get-up.”
After exhibiting and describing the bird-skins, he showed a large number of slides illustrating different phases of bird-life. The first of the slides depicted a colony of terns in the Rakaia River bed. These birds, he said, began to arrive early in October, and finally settled down on the shingle-bank thirty to fifty thousand strong. About the end of October they went up the river to select breeding-grounds. They displayed marvellous discretion in choosing spots not likely to be flooded by freshes in the river. The nests were built of small pebbles of a colour which strongly resembled the tintings of the young. From his own observations, the lecturer concluded that these birds would devour any eggs not in the nests. Another peculiarity was that, while the adult birds contented themselves with “silveries” found in the river, they went out to the sea for sprats for their young: probably the sprats were more nutritious. A picture illustrating the tern's sailing flight was displayed, and the lecturer pointed out the remarkable resemblance of the bird in that attitude to the monoplane.
Keas, he said, inhabited high country, showing a preference for localities with scrubby bush and shingly mountain-slopes. They stayed in dark valleys, and emerged at nights, or when anything excited their curiosity. There was no more inquisitive bird than the kea. He would come within a couple of feet of a stranger, and pick at his boot-laces to see what they were made of. Of all the birds he knew, the kea was the most amusing. Five of these interesting birds he had in captivity would throw up tins merely for the fun of hearing them rattle when they came down again. He also showed a lantern-slide depicting a kea standing on the edge of a rock with a sheer fall of 150 ft., dropping chips and pebbles over the face in an ecstasy of whimsical delight. Another picture showed a male and female kea on top of a stump, and the female scratching her mate's head with her beak.
One very interesting photograph was that of the rifleman, the smallest of our native birds. So small is it that Mr. Stead had discovered one making a nest in a 2 in. augerhole in a gate-post. The picture showed the female bird just entering the nest, in a hole in the trunk of a large tree.
Several pictures of blue or mountain ducks were shown, the lecturer stating that were they not so tame they would probably be more numerous.
The female sparrow-hawk, he said, displayed extraordinary ferocity in the protection of her young. If any one approached within a hundred yards of her nest she would swoop down at the intruder from a great height. If any one were watching her, she would approach within a foot and mount upwards again; if any one were not watching, however, she would strike at his head with her claws as she passed. The common harrier was much more of a coward, and if disturbed on its nest would utter a protesting squawk and fly away. Mr. Stead showed by specimens which he produced that the female sparrow-hawk was much larger than the male, as was the case with all falcons. In New Zealand there were supposed to be two distinct varieties, and he said he was endeavouring to prove that the larger bird was the female and the smaller the male of the same variety. His largest specimen coincided with the largest dimension given by Buller for the female bird, and his smallest specimen coincided with the smallest dimensions given for the male. He had found two birds of those descriptions mating, and that, to his mind, disposed of the theory that there were two different varieties in New Zealand.
The spotted shag fed entirely at sea, and the speaker entered a protest against the organization of shooting parties which visited the Heads and shot hundreds of old birds, leaving the little ones in the nests to starve. The big black shag built its nest overhanging the water, so that on the slightest alarm the young ones could drop over the side and dive out of harm's way. The adult birds used the same nests year after year, so that in the course of time they became quite prodigious structures. A remarkable series of pictures was shown illustrating the manner in which the young shags clung to branches by their feet, wings, or chins.
The albatros Mr. Stead described as a perfect aeroplane. Once started upon its flight, and provided it made no mistake, it should be able to continue its sailing without once flapping its wings, either against the wind or with it. The remarkable mode of this particular bird's flight was minutely described. It often happened, however, that, owing to the whirls, vortices, and eddy-currents close to the water being so intricate, albatroses, even after years of flight, were baffled and thrown out of their reckoning, and had to flap their wings to counteract the unexpected influences. An excellent photograph of a wandering-albatros was shown, and this was described by the speaker as the long section of a perfect racing-yacht.
The lecture concluded with a series of pictures of native bush. Mr. Stead explained by means of these the haunts and habits of various native birds—from pigeons, which delighted in low berry-bearing scrub furnished with tall trees, to the grebe, which built a floating nest upon the edge of a remote lake or lagoon, and anchored its home to a strand of flax.
A hearty vote of thanks was accorded the lecturer. In seconding the motion, Dr. Cockayne congratulated Mr. Stead upon his extremely accurate account of native bird life and habits. He said it was one of the scandals of our beautiful country that such beautiful birds as the shags (except where there were trout-streams) should be permitted to be destroyed. At Stewart Island, where there were no trout, the beautiful Stewart Island shag was being shot out by pot-hunters. We tried to attract tourists to inspect the wonders of our country, and yet little or nothing was done to protect the native-bird life.
Paper.—“On a Supposed Relation between Atmospheric Carbondioxide and the Development of Plant-surface,” by S. Page.
This paper is an attempt to explain the evolution of leaves as resulting from a gradual decrease in atmospheric CO2.
Taking the percentage of CO2 in air as 0.04, and of carbon in the earth as 0.02, every 8 in. in depth of the earth's crust contains carbon equal to that in the air. The CO2 locked up in Cambrian and later limestones and in fossil vegetable matter exceeds that at present in the atmosphere more than twenty thousand times.
Most of this carbon was probably thrown into the air during the earth's high-temperature period, any carbides formed being oxidized by metallic oxides and silicates; and has been again progressively removed by peat and carbonate formation largely since Cambrian times.
Any great and continuous change in a vital part of the environment, if not fatal to the organism, if the balance is preserved, must be accompanied by a corresponding change in the organism.
The part of plants mainly concerned in the progressive diminution of CO2 is the surface, and balance might be retained in two ways—(1) by increased effectiveness of a given area as a CO2 collector; (2) by increase of surface-area. The second—increase of plant-surface—is claimed to have occurred.
The earliest-known dominant plants were relatively massive, branchless, and leaf as, with a small ratio of surface to mass. Branching and leaf-development came in gradually. Leafy plants were not dominant till late Carboniferous times, while the present dominant plants are excessively leafy.
Ferns developed considerable surface very early, owing possibly to the large surface necessary to shade-plants in order to collect sufficient light. This factor—deficiency of light—was probably at work long before CO2 became scarce. Hence the early development of surface in ferns.
The subject-matter of the paper was subsequently discussed by Drs. Cockayne and Chilton and Mr. Speight, and the author replied to the criticisms which had been directed against his general conclusions.