Lesser Scaup

Aythya affinis (Eyton, 1838)

Photo © Brian Orr

STATUS

Nearctic. Polytypic.

OVERVIEW

Species not admitted nationally during the period covered (BOU 1971).

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NOT PROVEN

0). Pre 1851 Greater London Locality unknown, shot, undated.

(Thompson, 1849-51).

[BOU, 1971].

History Thompson (1851 (3): 140) under 'American Scaup Duck,' says: 'The American Scaup Duck (Fuligula mariloides, Vigors), about the specific distinction of which from the Common Scaup, ornithologists are not generally agreed, has a place in the British catalogue, from the circumstance of a single individual having been purchased in a London market.'

Comment Lacks adequate details of where and when shot and by whom. Not acceptable.

0). 1957 Berkshire Sutton Courtenay, male, intermittently, December to March 1960, when shot.

(C. Perrins, British Birds 54: 49-54, plate 9; C. A. Norris, British Birds 54: 166-167; A. R. M. Blake, British Birds 54: 167; C. E. Ford, British Birds 54: 167-168; E. M. Nicholson, British Birds 54: 168-170; C. E. Ford, British Birds 54: 256; W. D. Campbell, Report of the Oxfordshire Ornithological Society on the Birds of Oxfordshire and Berkshire 1957: 24-25).

[W. D. Campbell, Report of the Oxfordshire Ornithological Society on the Birds of Oxfordshire and Berkshire 1958: 20; Mrs. Radford, Report of the Oxfordshire Ornithological Society on the Birds of Oxfordshire and Berkshire 1959: 13; C. E. Ford, British Birds 54: 256; Not in BOU, 1971]

History C. Perrins (1961) in British Birds, Vol. LIV. pp. 49-54, says: 'During the past four winters there have been a number of observations in Britain of ducks that were thought to be Lesser Scaups (Aythya affinis), a North American species not recorded in Europe. This note is based on a detailed examination of one of these - that first seen at Sutton Courtenay, Berkshire, in December 1957 and subsequently watched by a very large number of observers. This bird was present for three to four months in each of the winters 1957-58, 1958-59 and 1959-60, disappearing at the end of March in the first two. During this time there was little change in its plumage and it is safe to assume that by March 1960 it was in full adult dress. It was clearly a drake.

Soon after it had been identified as a Lesser Scaup, two Americans, Drs. R. A. MacArthur and F. A. Pitelka, saw the bird and thought that it was not a Lesser Scaup. They gave head shape and large size as the reasons for their decision. British ornithologists became divided on the matter, many still believing that it was a Lesser Scaup, but some considering it to be probably a hybrid. As opinions differed so widely, it was eventually decided to obtain a permit to collect it. It was shot on 3rd March 1960, under a licence issued to Dr. I. C. T. Nisbet by the Nature Conservancy.

Comparison with live specimens at Slimbridge and with museum material at Oxford then confirmed the belief that it was not a Lesser Scaup, for the following reasons:

(a) Size. In the field it had appeared a little longer than Tufted Ducks (A. fuligula) it accompanied and considerably "broader in the beam" when seen end-on. If the Slimbridge specimens of Lesser Scaup are representative, this species truly qualifies for the name "Lesser", as these birds are distinctly smaller than the Ring-necked Ducks (A. collaris) which are on the same pool and which are comparable with Tufted Ducks in size....

(b) Shape of head. The forehead rises fairly steeply and the highest point of the head is almost immediately above the eye, whereas in the Lesser Scaup the forehead rises more steeply, the head is more domed and the highest point is behind the eye. There is a "kink" in the nape, rather similar to that in the Ring-necked Duck, but further down the back of the head than in the Lesser Scaup. This "kink" is at the termination of a small crest of feathers which hug the contours of the head so closely that I only once saw it blown aside in the field.

(c) Colour of head. In the field the head showed black with a strong brownish-purple gloss; in the hand it can be seen that the feathers are a deep coppery brown and in some lights have a purple gloss. The head of the Lesser Scaup is black with a purple or sometimes a greenish gloss, but there is no brown coloration in the feathers.

(d) Mantle. In the field the mantle appeared a drab, uniform grey; at close quarters or in the hand it is possible to see that this is caused by a fine, dark grey vermiculation on a pale, whitish ground (plate 9). Both Scaups have a much more heavily patterned, far less uniform back on which the barring is visible at some distance in the field. (For later reference it is necessary to note that the black back of the Tufted Duck shows a fine peppery vermiculation).

(e) Bill. In life and when the bird was freshly dead, the bill was bluish with a broad black tip and base (Fig. ic). It is almost parallel-sided, the breadth at the tip and base being, respectively, 21 and 20.5 mm. Both scaups have markedly spatulate bills with black only on the nail (Figs. 1a and ib).

(f) Wing-bar. The white wing-bar extends from the secondaries along the primaries where it is less pure in colour. Though obvious in flight it gave a far less sharply contrasting black-and-white appearance than that of the Tufted Duck. This is due in part to there being a fine stippling of grey in the rather dirty white of the secondaries (as is found in the Pochard) with no sharp delineation between pure white and the black tips as is found in the Tufted Duck and the Lesser Scaup. In fact there is scarcely any sign of tips of darker colour on the inner secondaries, while the outer ones have only rather indistinct tips. The Lesser Scaup has a white wing-bar on the secondaries, but it does not usually extend on to the primaries, though this is variable.

(g) Colour of eye. The eye was amber, more orange than in the Tufted Duck or either of the scaups.

These characters also preclude the possibility of its being any other known species. Presumably, therefore, it is a hybrid. The adherents of this theory were divided over the question of the bird's possible parentage. A paper by Voous (1955) describes two supposed Tufted Duck x Common Scaup hybrids and their resemblance to Lesser Scaup. The present specimen, however, is presumably a hybrid between a Tufted Duck and a Pochard. Within the genus Aythya a crest is found only in the Tufted Duck (though there is a small one in the Ring-necked Duck) while a red head, a deeper-than-yellow eye and a black base to the bill occur only in the Pochard and the Canvasback (A. valisineria). The Tufted Duck x Pochard view is strongly supported by the fact that all the characters (a-g) listed above are found in one of these two species or are intermediate between them and that there are no other characters which disagree with this. It has been possible to exclude all the other species of Aythya (including Ring-necked Duck and Canvasback) as likely parents, because each of them possesses one or more additional characters, some of which might be expected to appear in a hybrid, but which are not present in this specimen. A detailed description of the specimen appears in the appendix on the next page.

It is worth noting that these two species, Pochard and Tufted Duck, are the only two members of this genus which breed in Britain and that they are commonly found nesting by the same pieces of water. Thus they have the greatest opportunity, from the distributional point of view, of producing hybrids which will later be seen in Britain. Gray (1958) lists this cross as having occurred in both directions and states that fertile drake hybrids have been recorded. It is therefore probable that more of these birds will be seen in the future and, if they are fertile and breed, some even more confusing specimens may occur through back-crossing.

As mentioned above, Voous (195 5) recorded two specimens (both in the Zoological Museum of Amsterdam) of Tufted Duck x Common Scaup hybrids. The photographs and descriptions of these, however, suggest a marked similarity to the Sutton Courtenay specimen and might easily be confused with it. Further evidence of the occurrence of Tufted Duck x Pochard hybrids was recently provided by Bezzel (1960). Watching on the Ismaning, near Munich, Germany, he recorded such hybrids in eight of the years between 1934 and 1959. His descriptions of these birds differ little from that of the Sutton Courtenay specimen, though some were noted as having red eyes and the crest was not always evident. In April, during migration, there are often many more female than male Pochard in that part of Germany and a few more male than female Tufted Duck. He suggested that it is at this time that the hybrid pairs are formed. Some displays of the two species are rather similar and a display shown by a hybrid male resembled parts of the displays of each parent species. In addition, a hybrid was seen displaying to a female Pochard and he described the supposed offspring of a hybrid x Pochard back-cross. Bezzel's paper also includes references to other records of hybrids.

In view of the confusion which the Sutton Courtenay specimen caused among ornithologists it would seem that any future reports of Lesser Scaup must be treated with extreme caution and that exceptionally good views of all the characters of this species would be essential before the admittance of the Lesser Scaup to the British and Irish List could even be considered.

Among the many ornithologists with whom I have discussed this specimen I am particularly grateful to Drs. I. C. T. Nisbet and A. J. Cain for their comments and for the latter's permission to use for comparison the material in the Oxford University Museum where the specimen (No. B/4171) is now lodged.'

Comment Hybrid.