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A History of the Birds of New Zealand.

Stercorarius Crepidatus. — (Richardson’s Skua.)

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Stercorarius Crepidatus.
(Richardson’s Skua.)

  • Larus crepidatus, Gmelin, Syst. Nat. i. p. 602 (1788).

  • Stercorarius crepidatus, Vieill. N. Diet. d’Hist. Nat. xxxii. p. 155 (1819).

  • Lestris richardsonii, Swains. Fauna Bor.-Am. p. 433, pl. 73 (1831).

  • Lestris parasiticus, Bonap. Consp. Av. ii. p. 208 (1857, nec Linn.).

  • Lestris longicaudata, Finsch, J. f. O. 1872, p. 126 (nec Briss).

  • Stercorarius parasiticus, Buller, Birds of New Zealand, 1st ed. p. 268 (1873, nec Linn.).

Ad. (exempl. ex N. Z.) suprá cinerascenti-brunneus, tectricibus alarum saturatioribus, supracaudalibus exterioribus versùs basin albicantibus: pileo summo pallidiùs brunneo, plumis albicante obsoletè terminatis: facie laterali, gulâ et collo postico albis, plumis versùs apicem brunnescentibus: corpore reliquo subtùs albo, hypochondriis cum crisso et subcaudalibus cinerascenti-brunneo lavatia: subalaribus et axillaribus cinerascenti-brunneis: remigibus brunneis, extùs nigricantibus, intùa ad basin albidis, scapis brunnescenti-albis, exteriorum purè albis, secundariis intimis dorso concoloribus: caudâ saturatè brunneâ: rostro saturatè brunneo: pedibus cinerascenti-nigris: iride nigrâ.

Ad. Crown, nape, and sides of the head dull greyish brown; neck all round, breast, and sides of the body greyish white; shoulders, and all the upper surface, dark olivaceous grey of different shades; primaries and tail-feathers blackish brown, the former with white shafts; inner surface of wings, axillary plumes, and abdomen ashy grey tinged with brown; some of the under tail-coverts uniform ashy grey, others white barred with grey. Irides black; bill dark brown; tarsi and toes greyish black, the claws darker. Length 16·5 inches; extent of wings 38; wing, from flexure, 11·75; tail 5·5; bill, along the ridge 1·2, along the edge of lower mandible 1·7; bare tibia ·5; tarsus 1·6; middle toe and claw 1·5.

Young (N.-Z. example). General upper surface blackish brown, more or less varied with pale brown and fulvous, many of the feathers having pale margins; crown of the head and hind neck brownish grey, the former with narrow linear black markings, and the hind neck washed with fulvous brown; the edges of the wings speckled with white; the upper tail-coverts fulvous white, each feather with two broad irregular bars of brownish black; primaries brownish black with white shafts, also white on their inner webs towards the base; tail-feathers brownish black, perceptibly darker towards the tips, and pure white at the base under the coverts; entire under surface greyish white, thickly speckled and freckled on the fore neck, breast, and abdomen with brown; the axillary plumes, the sides of the body, and the under tail-coverts washed more or less with fulvous, and marked with broad, transverse, somewhat unequal, bars of blackish brown. Bill greyish black; legs and feet brownish black, with a conspicuous yellow spot towards the base of the inner interdigital web.

Obs. In the adult example described above, the two middle tail-feathers are being reproduced, and present a remarkable denuded appearance (see woodcut in Trans. N.-Z. Inst. vol. xi. p. 358). In the young bird the tail-feathers are broad and acuminate, the two middle ones extending about half an inch beyond the rest.

The above description of the adult is taken from an example shot by myself on the sea-beach at Horowhenua, in the provincial district of Wellington, on the 30th of April, 1864, and presented to the Colonial Museum with the rest of my original collection.

When I published my former edition this was the only known instance of its occurrence in New page 67 Zealand. Three subsequent cases have been recorded. A young bird in the flesh, received by Sir James Hector at the Colonial Museum, was noticed by me at the time, in the ‘Transactions of the New-Zealand Institute’ (vol. vii. p. 225); another young bird was shot in Wellington harbour in January 1877; and a third example, in more mature plumage, was picked up on the beach at Cape Campbell, by Mr. C. H. Robson, in November 1877. The two last-mentioned specimens being in my collection, I was able to submit them to Mr. Howard Saunders, who unhesitatingly referred them to Stercorarius crepidatus, and I feel bound to accept the determination by one who has made this group of birds his special study *

On comparing the two adult birds there is a manifest difference in the coloration, the one described above having the breast greyish white, and the abdomen ashy-grey tinged with brown, whilst the other has the entire under surface white, marked on the breast and sides with interrupted bars of sooty brown. In both, however, the under surface of the wings and the axillary plumes are of a uniform dark ashy grey. These individual differences are thus accounted for by Mr. Saunders in treating of S. crepidatus (P. Z. S. 1876, pp. 328, 329):—“It is now well known that there are two very distinct plumages to be found in birds of this species, even in the same breeding-places—an entirely sooty form, and one with light underparts,—and that white-breasted birds pair with whole-coloured birds as well as with those of their respective varieties. If this species is ‘dimorphic,’ the offspring of one particoloured and one white-coloured bird ought to resemble one or other of their parents without reference to sex; my examination of upwards of a hundred specimens from widely different localities and in all stages inclines me to the belief that this is not the case, and that the young of such union will be intermediate, whilst the offspring of two similar parents will ‘breed true.’ This point can only be solved by some ornithologist who will devote his attention to a colony during the breeding-season, observing the produce of all these unions, and, if possible, marking the nestlings before they take wing… . It is worthy of notice that in Spitzbergen, its most northern breeding-ground, neither Dr. Malmgren nor Professor Newton found a single example of the dark whole-coloured form; all those which Admiral Collinson’s and Dr. Rae’s Expeditions brought home from the far north are also white-breasted specimens, which looks as if the dark form was a more exclusively southern one.”

* In my former edition I referred the first-named example to Stercorarius parasiticus, Linn., and added the following remarks:—“Dr. Finsch, to whom I submitted the skin, is of opinion that it is an immature bird; and Mr. Howard Saunders, who has made the Laridæ his special study, expresses his conviction that it is a new and hitherto undescribed species. I am rather disposed, however, to consider it an aged female of the species known as Buffon’s Skus, with the plumage much faded and worn, indicating a sick or exhausted condition of body. I may add that the two middle tail-feathers are only partially developed, being encased in a sheath at the base. They extend only about an inch beyond the rest, and are much abraded, having a peculiar filamentous appearance.”

Professor Hutton, adopting another view, wrote to me:—“Your Lestris is no European bird, but appears to be a representative of the Arctic Skua. I think it is a young bird.”

Commenting on my account of this bird, Mr. Saunders, in his paper on the Stercorariinæ (P. Z. S. 1876, p. 330), said:—“His general description suits S. crepidatus; and he expressly states that the shafts of the primaries are white, the characteristic which particularly serves to distinguish it from Buffon’s Skua, with which he has identified it. At the time that I examined the specimen in question I was not aware of this distinctive feature: the skin also had been badly preserved; and, to make matters worse, the plumage was so worn and abraded that it is a marvel that the bird was able to fly at all.” Referring thereto, in a communication which I afterwards made to the Wellington Philosophical Society, I observed:—

“Mr. Saunders has evidently, in this case, trusted more to his memory than to the notes which, we may assume, he would make on examining a novel specimen—one which, in fact, he took to be ‘a new and hitherto undescribed species.’ It will be seen, at a glance, that the specimen now before the meeting (which passed through Mr. Saunders’s hands in the same condition) instead of being a ‘badly-prepared’ skin is a first-class cabinet specimen, and that, instead of having ‘the plumage so worn and abraded as to make it a marvel that the bird could fly at all,’ the wings are in perfect plumage, the only abraded feathers being about the head and neck, which could not well affect the flying capabilities of the bird.” (Trans. New-Zealand Inst. vol. xi. p. 356.).