Among New Zealand’s many bird curiosities, writes Edgar Stead, the wry-billed plover is often not included, but it certainly ought to be, for it is the only bird in the world which has its bill bent sideways. The crossbills of the Northern Hemisphere might claim that they share in this distinction, but their bills are symmetrical, the upper mandible being bent one way, and the lower, the other.
In the wrybill, however, the bill, which is one and a quarter inches long, is bent to the right in the middle, the end being offset at an angle of 12 degrees to the base. This is claimed to be an adaptation to its existence on the shingle river-beds of Canterbury, where it nests, the bent bill supposedly enabling it to get its food the more readily from under stones. And no doubt it does this, when the occasion demands, but there can be very few occasions when this peculiarity is of any decided benefit to its possessor, for over nearly all the river-beds on which the bird feeds, the stones are so much buried in sand as to make the bill quite unnecessary. Moreover. the bird spends less than half the year on shingle river–beds, living for the remaining months on mud–flats, and sea beaches, where its abnormality can be of no benefit.
In those localities on the river-beds, where a diminishing stream leaves large shingle, there the bent bill is of some use. In such situations I have seen wrybill peck under a stone on its left, and then turn around to get the same stone on its right, and peck under it again. It must be admitted, however, that I have often seen banded dotterel act similarly, and, I daresay, just as often as I have seen wrybills do it, so that any advantage the wrybill has would seem to be very slight.
It has to be taken into account also, that while the bill, bent as it is to the right, gives the bird some advantage when feeding under stones on its right, this structure is a very distinct disadvantage to the bird when it wishes to feed on its left. A bill with an upwards curve, one would have thought, would have been of greater use.
In most writings on the wrybill, the greatest emphasis is laid on the importance of its peculiar bill, but, in my opinion, its colouration is far more important, for this harmonises so perfectly with that of rounded stones among which it breeds that if the bird remains stationary (and it has a habit of doing so) it becomes exceedingly difficult to detect.
Wrybills leave the South Island for the winter, returning to Canterbury during August, and immediately take up their abode on the shingle river-beds. Very little is on record (1932) as to their summer distribution, and this is not surprising for the birds themselves are inconspicuous, and their haunts are not much frequented by man. One would expect to find them nesting on the Opihi and the Waitaki, though I have never heard of them doing so; and they may occur on the Awatare and the Wairau in Marlborough, but so far as my personal knowledge goes, the breeding grounds are confined to a limited number of rivers in Canterbury. I have seem them on the Rakaia River from its mouth up to where the Acheron flows in — say five miles above the gorge; on the Waimakariri up to the Gorge Bridge; on the Hurunui River, below the Culverden Road; on the Waiau River above Waiau, and on the Rangitata River near the traffic bridge. I know they frequent the Ashley, and I have been told that they were seen on the Clarence, though this latter record was not substantiated. It may be taken as reasonably certain that they breed on these rivers, wherever there are suitable and sufficiently large areas of bare shingle near water. Those are the two desiderata of the wrybill for its nesting site: considerable areas of bare shingle, which must be situated near water. The great increase in the quantity of exotic plants in our river–beds has probably adversely affected the wrybill more than any other species. Banded dotterels, oyster–catchers, stilts, terns and gulls — all these have other nesting sites as well as bare shingle spits, but the wrybill has none, so the introduction of the yellow lupin was a very serious thing for it.
Wrybills are in their full mating plumage when they return south, the black band across the chest being very conspicuous; the narrow white frontal band, with the brownish band behind it, not showing up at all except at very close range. The whole of the upper parts are blue–grey, but with age the feathers lose a certain amount of their blue tint, and also, particularly in the case of scapulars, become much frayed at the edges. It has been stated by some writers that the black chest band is wider on one side than the other, but this is not the case, either in fact or in appearance.
Mating commences as soon as the birds arrive in the south, and during the proceeding the birds are very active, chasing each other about in the air, and also on the ground, and occasionally actually coming to grips. Sometimes a pair may be getting along nicely with their courting, when another bird will arrive on the scene, and then the bird of the pair which is of the same sex as the stranger will proceed to drive it away, running after it, with neck outstretched, in and out among the stones, every now and then opening its wings slightly to help it maintain its balance. Occasionally two birds will run thus at top speed for twenty or thirty yards, their little legs going so fast as to be quite invisible. Later, when they are mated, the cock birds have the same habit as the cock banded dotterel, of ordering their mates about by running up to them, drawing themselves up to their full height, and puffing out their breast feathers. It is very interesting that these two birds should have this same habit. It is possible that it is descended from a common ancestor away back in the family lineage; or perhaps only one of them used to do it, and the cock birds of the other species, constantly associated with them on the river–beds, saw how wonderfully it worked — noted with envy and admiration the meek and immediate submissions of the hens, and the constant obeying of their orders — and decided that the gesture was well worth cultivation. At any rate both species have it; and what if the attitude should strike us humans as being a little over pompous; as showing, indeed, just a trifle too much self–satisfaction? It works far better in these bird families than our own efforts to ensure one head of each family — the much–discussed “and obey” of the marriage service.
Wrybills nest on high shingle spits, choosing a place where the stones are rather large, and clear of all growths and drift. A mere scratching in the sand, occasionally with a few small pebbles added around its edges, serves as a receptacle for the two eggs, which are wonderfully like the stones among which they are laid.
Both birds take their turn at incubation, and sit very close, so that they will often allow a person to pass within twenty yards of them without getting off the eggs. Owing to the remarkable similarity of their colouring to that of the surroundings, wrybills are easily passed when they keep still, and nests would certainly remain undetected if the birds did not move. But if the bird does get off the nest, and run towards an intruder (wrybills do not fly around intruders in the same way that banded dotterel do), the latter has only to stand still for a few moments, when the bird will, as a rule, run straight back, and sit on its nest, even though it be in full view, and not fifteen yards away.
Laying commences about the middle of September and continues throughout October. I have found eggs in November, but I think it probable that they were second clutches, the first having been destroyed. The young when hatched are thickly covered with down, white on the breast and underparts, the whole of the upper surface being stone grey, faintly marked with smoky black. When they are hatched, and even as an embryo in the egg, they have the bend in the bill well defined. They leave the nest within a day of hatching, and follow their parents about in search of food. By the time the young are full grown, the old birds are moulting into their winter plumage, when they closely resemble the young — having no black chest band, and no frontal bands — and then old and young leave the river–beds. The earliest families have left by the end of December, and all of them have gone by the end of February. Sometimes they stay awhile on the coastal lagoons, and I have several times seem them on the shores of Lake Ellesmere in January and February, but they are the first birds to go north, migrating nearly two months earlier than the main body of dotterel and stilts. They spend the winter on the sea coast of the North Island, frequenting the mouths of rivers, and the mud–flats of the big harbours of the far north. So far as my information goes, it would seem they travel up the west coast of the North Island in greater numbers than they do up the east.
Wrybills always display when their eggs or young are handled, running around with the wing near the intruder trailing on the ground, the other lifted in the air; the feathers of the rump are raised; the tail spread fanwise, and depressed so that the tip is almost on the ground; and the bird all the time makes a continuous purring noise.
Their normal call is a high–pitched staccato whistle resembling that of the banded dotterel, though it is rather more musical. The wrybill does not, however, call nearly so frequently as the dotterel, either when on the ground or in flight.
As to the wrybill’s chances of survival, one would say that they are good, at any rate on those rivers whose beds among the hills above the gorges are sufficiently wide to be of the bird’s liking, for there the winter temperature seems to have prevented the yellow lupin from getting a foothold. But the open shingle must be a quarter of a mile wide before the wrybill would make their home on it. They were never numerous, and even thirty years ago I should think two to three pairs to the square mile on the Rakaia was their maximum population, and, since the lupin has filled the river bed, below the bridge, their numbers have certainly been much reduced. Their chief bird enemies are harriers and black–backed gulls, yet the toll that both these take would not equal that of stoats and weasels during the birds’ breeding season.
It is sincerely to be hoped that this most interesting little bird does survive, for, on its nesting ground, it exhibits in all its stages — adults, eggs and young — the most amazingly perfect protective colouration that there is among New Zealand birds.
Other common names: —
20 cm., 55 g., pale grey upper parts, black bill, legs grey green, white forehead tinged with black in breeding plumage, breeding adult underparts white except for black band across the chest.
Where to find: —
The main breeding rivers in the South Island are the Rakaia, Rangitata, Waimakariri, and upper Waitaki. After breeding the head to the tidal harbours of Northland, Auckland, and South Auckland, the Firth of Thames.
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Illustration description: —
Buller, Walter Lawry, Birds of New Zealand, 1888.
Heather, B., & Robertson, H., Field Guide to the Birds of New Zealand, 2000.
Stead, Edgar F., Life Histories of New Zealand Birds, 1932.
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Saturday, 7 June 2014; ver2009v1