A study of certain hybrids ERIC GILLHAM, JAMES M. HARRISON and JEFFERY G. HARRISON

Summary Six distinct types of drake Aythya hybrids which may be seen in Britain are described both from museum specimens and as seen in the field. These are the progeny of various combinations of four species: Pochard, Tufted , and Scaup. A description is also given of a drake hybrid between two North American species, the and Ring-necked Duck. Female Aythya hybrids must often remain unrecognised: four specimens are described. The relatively frequent occurrence of hybrids resembling species rarely found in Britain necessitates very careful scrutiny of all records purporting to be of , Ring-necked Duck and Ferruginous Duck.

Introduction one or other of the parent species is so The problem of hybridisation among the close that they are likely to be overlooked. of the genus Aythya was We have, however, examined one skin of a brought into prominence in this country female Pochard X and by the now famous ‘Lesser Scaup’ dispute, watched female Paget’s Pochards in the in which a , eventually obtained at field. Sutton Courtenay, Berkshire, was finally i . P o c h a r d A. ferina X T u f t e d D u c k identified as a hybrid, probably between a A. fuligula, o ‘L e s se r S c a u p T y p e ’ . The Pochard Aythya ferina (Linnaeus) x Sutton Courtenay specimen. (See Plates Tufted Duck Aythya fuligula (Linnaeus). 16, 17, 18 in Photographic Section I, The hybrid was described by Perrins opposite page 64.) (1961), in comparison with a Lesser Scaup The description and relevant compari­ Aythya affinis (Eyton), but no attempt was sons have already been published else­ made at that time to compare it with other where (Perrins, 1961). These include the Aythya hybrids, of which there are at least important differences of colour, pattern six types to confuse ornithologists in and measurements between this bird and Britain today. For this reason we have the Lesser Scaup A. affinis, and also a brought together a series of field observa­ description of the bill colour, stressing the tions on these and have linked them with a presence of black at the tip and base, comparative study of all the specimens we pigmentation which is absent in A . marila could assemble. and A . affinis, in which the nail only is These different types may be loosely black. The importance of the wing-bar is defined as a ‘Lesser Scaup type’ (if one stressed as this reflects the intermediate accepts the fact that the Sutton Courtenay character of the individual. Similarly the bird resembles that species to some extent) ; iris is stated to have been intermediate in a ‘Pochard type’; a ‘Tufted Duck type’; a colour. ‘Baer’s Pochard type’; a ‘Scaup type’, and There would be little point in repeating ‘Paget’s Pochard’ or a ‘Ferruginous type’. the detailed description of the plumage of As a result of our studies, we are able to the specimen which appears in the Appen­ confirm the correct diagnosis of the Sutton dix to Perrins’ paper (loc. cit. p.53). In our Courtenay bird, the parentage almost opinion the identification of the specimen certainly and rather surprisingly being is correct, i.e. it is a presumptive hybrid Pochard Ç X Tufted Duck

AYTHYA HYBRIDS 49 T able I» Mmseuam specim ens o f Aythya hybrids examined in this study» Ref. Observations No. Hybrid and Type Data Reference re parentage I. Pochard x Tufted 3 Mar. i960. Sutton Perrins An identical hybrid of Duck (‘Lesser Scaup Courtenay, Berkshire (1961) known parentage type1) S Oxford University Pochard $ x Tufted Museum B.4171 Duck parentage Pochard S X 7. Pochard x Tufted 2 Mar. 1962. J. M. * Tufted Duck $ and Duck (‘Tufted Duck Harrison collection. were bred by T. Jones type’) ad. Bred in captivity 8. Scaup x Tufted Duck - Dec. i960. B. L. Sage Of known parentage (‘Scaup type’) Sage collection.

5 0 THE WILDFOWL TRUST 12mm. on the edges of the culmen on Courtenay bird grey, tipped brown.) either side (ef. sketch, loc. cit. p.51). Axillaries and under wing-coverts, white; 2. P o c h a r d A. ferina x T u f t e d D u c k fore edge of wing grey. (Sutton Courtenay A. fuligula, $, ist w. ‘L e s se r S c a u p bird paler.) T y p e ’ . (See Plates 19, 20, 21.) Primaries: sepia, outer vanes and tips November 23rd, 1962, Sevenoaks, Kent. dusky. (Sutton Courtenay specimen very Harrison collection. pale brownish-sepia, outer vanes and Crown, head and neck: strong purplish- tips dusky.) red, darker on the chin and on front of Flanks: pale grey, vermiculated white. neck ; a well marked white chin spot. (The Measurements (in mm.) Sutton Courtenay bird is possibly a little Wing: 224 brighter on these parts, but has no chin Bill: spot.) A distinct but stubby crest, which is length from feather margin 44.5 also present in the Sutton Courtenay width at nostrils 18 specimen. Upper breast: purplish-black; width at widest point 20 at lower edge, narrow whitish crescentic nail 9 X 7 markings to feathers. In the Sutton Tarsus: 37 Courtenay bird this area is a little brighter Middle toe without nail : 58 and the white crescentic markings are Specimens 1 and 2 agree very closely; more pronounced. Over shoulder regions the difference appears to be due to advanc­ blackish-slate with minimal purplish-red ing maturity in the Sutton Courtenay reflections, which are slightly stronger specimen. laterally; lower edge wedge-shaped on 3. P o c h a r d A . ferina x T u f t e d D u c k mantle, the apex somewhat brownish, A. fuligula, (J, ad. ‘P o c h a r d T y p e ’. (S e e directed towards the tail. In the Sutton P la tes 22, 23, 24.) Courtenay bird this area is brighter and March 28th, 1937. Lake near Ismaning, shows fairly strong purplish-red reflec­ Bezzel Collection. Munich Museum, Regis­ tions; the lower edge is the reverse to tered No. 37.106. that of the Sevenoaks specimen. Breast: Crown, head and neck: rather deep rich whitish, flecked greyish-brown, particularly chestnut-red, reflecting some purple, on the right side ; left side less flecked, but weakly on the face, but strongly on the a strong slate-coloured spot towards the back of the neck; chin and front of neck vent. (Sutton Courtenay bird is more dull sepia faintly reflecting green. This regularly flecked and spotted.) bird has a short truncated crest. Upper Vent: barred pale greyish-brown, also breast and over shoulders : purplish-black ; finely vermiculated grey (Sutton Courte­ at lower edge of breast, the feathers nay specimen is washed with brownish- narrowly edged silvery-white. Shoulder grey, but still shows barred effect and regions adjacent to mantle rather duller; paler greyish vermiculations here). central area extending on to mantle of Under tail-coverts: blackish-sepia (Sutton pale brownish-sepia. This area is roughly Courtenay bird pale brownish-sepia). triangular with the apex directed towards Upper parts: moderately dark grey, very the tail. finely and closely vermiculated white Lower breast and belly: white merging (Sutton Courtenay bird a trifle lighter and into grey belly, becoming darker at vent. brighter). Under tail-coverts : black. Rump and upper tail-coverts: blackish- Upper parts: rather a strong dark grey, sepia with very weak reflections, closely closely and finely vermiculated white. resembling Sutton Courtenay bird. Long scapulars similar, but longest darker Rectrices: greyish-sepia, outer vanes and and more uniform on inner vanes, tone tips a trifle darker. (Sutton Courtenay bird sepia. brownish-sepia, outer vanes and tips Mantle : as upper parts, on sides paler and slightly darker.) greyer than rest. Wing: coverts almost uniform greyish- Rump and upper tail-coverts : dull black. brown to sepia; greater wing-coverts at Rectrices: sepia. speculum darker (Sutton Courtenay bird Wing: coverts dark grey, very finely considerably lighter and greyer, and shows vermiculated, contrasting markedly with fine greyish vermiculations). the edges of adjacent mantle; edges of wing Speculum: whitish, broadly-edged below coverts at speculum somewhat darker. with strong sepia, extending on to pri­ maries. (Sutton Courtenay specimen Speculum: white, at lower edge speckled whitish, at lower edge greyish-sepia, grey; axillaries and under wing-coverts considerably specked whitish.) white, fore edge of wing faintly and Long scapulars: innermost uniform dark narrowly grey. sepia, longest paler brownish-sepia. (Sutton Primaries: bufiy-sepia, outer vanes and

AYTHYA HYBRIDS 51 tips darker sepia giving the extended wing Lower back, rump and upper tail-coverts : a light bar. dark purplish-brown. Flanks: white, very faintly and closely Rectrices: dark purplish-sepia. vermiculated pale grey. Wing: coverts almost uniform dark Measurements (in mm.) brownish-grey. Wing: 217 Speculum: grey, lower border narrowly Bill: edged sepia and tipped white. length from feather margin 44.5 Primaries : outer vanes and tips dark sepia, width at nostrils 20 rest of feathers palish-sepia, forming a width at widest point 21 broad pale wing-bar. nail 6 x 6 Scapulars: as upper parts generally, but Tarsus: 34 finely speckled, grey on proximal series Middle toe without nail : 57 and brownish-ash on tips of next in size, There is no record of the soft parts: a longest dark chocolate-brown. pattern is clearly visible on the bill, which Under-wing: axillaries and coverts white, was presumably bluish-grey with a black fore edge of wing mottled fulvous-grey. tip and black at the base. Measurements (in mm.) Comments: compared with the other two Wing: 203 drake hybrids of this cross, this bird Bill: presents much greater contrast. It is length from feather margin 42 closer in appearance, superficially, to a width at nostrils 19 drake Pochard, but has the truncated, but width at widest point 20.5 nevertheless noticeable crest. Possibly this nail 9.5 X 8.5 enhanced contrast is due to greater Tarsus: 37 maturity, but this is more likely to be a Middle toe without nail: 58.5 different type of hybrid resulting from the This is an intermediate type of female same parentage - i.e. A. ferina $ X A. hybrid. fuligula $ or one of these hybrids X A. 5 . A m e r i c a n R e d h e a d A. americana ferina. It has been found that sibling (Eyton) x R i n g - n e c k e d D u c k A. Wigeon A. penelope x Shoveler A. collaris (Donovan), $ by plumage. (See clypeata hybrids (Harrison, 1964) can Plates 16, 17, 18.) show quite marked individual differences It is of more than passing interest to be in colour. In this case, the general external able to make a direct comparison of the morphology of the ‘Pochard type’ hybrid is foregoing specimens with a similar hybrid so similar to the ‘Lesser Scaup types’ of the New World. The hybrid now dis­ described, the essential differences being cussed was reared at the Wildfowl Trust in colour only, that it is reasonable to and was found dead on 2nd February, presume the same parentage. (See also 1962. field notes, number 27.) Crown, sides of face and ear-coverts: 4. P o c h a r d A. ferina x T u f t e d D u c k coppery-red, brighter than in the Sutton A. fuligula, $ I ntermediate T y p e . ( S e e Courtenay specimen and as in that example P l a t e s 28, 29.) feathers narrowly tipped black. Throat January 4th, 1949, Hickling Broad, Nor­ rather dusky and there is a white chin spot, folk, Norwich Castle Museum No. 119.939 smaller than in A. collaris. (Lord Desborough Coll.). Sides of neck: at back and on occiput Crown, head and neck: dark chestnut strong dusky-green reflections, rest of brown, crown to nape and cheeks slightly neck as crown and face. darker; white chin-spot and imperfect Breast: black, glossed dark purple; this whitish facial mask not joining on forehead, colour extends upwards over the shoulders, i.e. confined to sides of face and freely where there is a suggestion of a pale spotted with chestnut. crescent as in A . collaris. On lower breast, Breast: pale Ecru-drab* (Ridgway, 1886, feathers tipped greyish-white. PI. I ll, No. 21), barred silvery-white. Belly and sides of body : pale greyish-white, Belly: silvery-white, obscurely barred and in the centre finely peppered black; on blotched with Ecra-drab. sides and flanks pronouncedly grey, very Vent: pale grey, Ecra-drab proximally. finely vermiculated greyish-white and Under tail-coverts : stronger brownish black. The flanks are narrowly-edged Ecra-drab, speckled grey and white on whitish, more distinctly so at the caudal tips. end. This character is clearly indicative of Flanks: whitish, barred obliquely pale A. collaris blood. fulvous and vermiculated grey and white. Vent: brownish-black, tips of under tail- Upper parts : warm dark chestnut-brown, coverts finely vermiculated brownish-grey. at shoulders bright chestnut-brown. Axillaries: white. * Capitalized names o f colours appearing later i . the text are also those of Ridgway.

52 THE WILDFOWL TRUST Under wing-coverts: large innermost that of the younger bird of 30th March, white, lightly vermiculated. grey-brown, 1959- but mostly white; rest white. Fore edge of Crown, sides of face and ear-coverts : wing grey, narrowly edged white. purplish-black, on sides of face and ear- Back: at edge of mantle a triangular area, coverts reflecting green ; the crest which is apex directed towards tail, of dusky-brown, shorter than that of A. fuligula males, but speckled finely with dull greyish-white. longer than ‘Lesser Scaup type’ hybrids, Rest of mantle dark dusky-grey, very finely is of the same purplish-red. vermiculated greyish-white. Neck: purplish-red as far as the mantle. Scapulars: as mantle, but vermiculations Mantle: dark brownish-ash, very finely more pronounced. vermiculated ashy-white, rest of upper- Rump and upper tail-coverts: dark parts dark sepia, finely vermiculated brownish-black. greyish-white. Rectrices: sepia. Rump and upper tail-coverts: uniform Wing: wing-coverts and bastard-wing dark sepia. sepia. Rectrices : dark purplish-sepia. Speculum: outer vanes of secondaries Breast: purplish-sepia, feathers narrowly forming the French-grey speculum paler edged ashy-white. at bases and more intense medially, where Rest of under parts : greyish-white, irregu­ also narrowly tipped white and edged black. larly barred transversely pale sepia, overall Primaries: outer vanes and tips, sepia; appearance dark. inner vanes pale brownish-sepia, forming a Vent: purplish-sepia. pale wing bar. Under tail-coverts: ashy-white, finely Scapulars: innermost as mantle and back; speckled pale sepia. longest dark sepia, dully reflecting metallic Flanks : ashy-white, washed pale cinnamon green. and finely vermiculated ashy-white. Measurements (in mm.) Wing: coverts uniform brownish-sepia. Wing: 226 Speculum: white, extending on to pri­ Bill: maries, edges of outer vanes narrowly length from feather margin 51 margined in sepia. width at nostrils 19 Primaries: brownish-sepia, tips and outer width at widest point 21 vanes dark sepia. nail i l X 8 Scapulars: innermost same as mantle, Tarsus: 38 longest warm brownish-sepia, dully reflect­ Middle toe without nail: 64 ing greenish-bronze. We would comment upon the following Axillaries: white, finely speckled greyish- points in this specimen: brown. 1. The broad similarity to ‘Lesser Scaup Measurements (in mm.) type’ hybrids. Wing: 212 2. The presence of a well marked chin Bill: spot. length from feather margin 43 3. Some characteristics referable to A. width at nostrils 22 collaris inheritance. width at widest point 23 4. The bill colouration which shows the nail i l X 8 presence of a black tip as distinct from a Tarsus: 39 black nail; this pigmentation extends Middle toe without nail: 63 to a depth of 16 mm. Specimen of 2nd March, 1962. 6 and 7. P o c h a r d A . ferina x T u f t e d Resembles the preceding bird, but is D u c k A. fuligula, ó'ó' ‘T u f t e d D u c k generally brighter from advancing maturity. T y p e s ’ . (See P la tes 10,16-21 and 30.) The breast-shield lacks the fine white The two specimens now to be described edges to feathers ; flanks are a richer shade are both captive of known parentage of cinnamon-brown and sides of face and age, from the same brood, the male reflect a stronger green; under tail-coverts parent being A . ferina, the female A. reflect a stronger purple. fuligula. Both were anatomically sexed Measurements (in mm.) male. They were hatched in 1958, one Wing: 224 dying on 30th March, 1959, the second on Bill: 2nd March, 1962. They are almost identi­ length from feather margin 40 width at nostrils 21 cal in plumage and, as can be seen from width at widest point 22.5 the plates, present a very different mor­ nail 10.5 X 9 phology to individuals in which the cross Tarsus: 37.5 was in the opposite direction. Middle toe without nail: 61.5 The description which now follows is Comments: The strikingly different mor­ a y t h y a h y b r id s 53 phology according to which way the cross innermost primaries and edged with dark goes is of considerable interest; in one case sepia. the resulting hybrid appears as a ‘Lesser Primaries: sepia, darker on outer vanes Scaup type’, in the other direction as a and tips. ‘Tufted Duck type’. The extremely dark Rump and upper tail-coverts: dark under parts in the latter are also note­ purplish-black. worthy. It seems that A . fuligula male Measurements (in mm.) characters are largely transmitted by the Wing: 222 female, while the exposure of the dark Bill: under parts is probably reversionary to­ length from feather margin 45 wards other dark-bellied Aythya species. width at nostrils 22.5 This same feature has been revealed in a width at widest point 25 female A . nyroca X A . fuligula (see nail 9.5 X 8 under Baer’s Pochard type), and in variant Tarsus: 40 female Tufted (Harrison 1961) and Middle toe without nail: 60.5 Scaup (Harrison 1962) in winter plumage. 9. Amsterdam Museum Specimen Reg. Both species normally have dark or darker No. 5050. under parts in summer. This specimen, when compared with 8, 9 and 10 . S c a u p A . marila (Linnaeus) X the preceding bird, is darker on the mantle T u f t e d D u c k A. fuligula,

54 THE WILDFOWL TRUST red, slightly darker on crown and nape; culated sepia, somewhat uneven in tone small white spot on chin. due to moult. Upper breast and over shoulders: a deep Rump, upper tail-coverts and rectrices: coppery-red. rich dark sepia. Above mantle: a broad area of dark Flanks: coppery-brown, mixed with grey purplish-red. and rather strongly vermiculated. Lower breast : light coppery-brown. Wing: coverts brownish-grey obscurely Belly: white, lightly speckled palest grey. vermiculated, quills slightly darker and Vent: sooty-grey, finely vermiculated with darker edges. Coverts at speculum paler greyish-white. slightly darker. Under tail-coverts: white, vermiculated Speculum: white, narrowly edged grey greyish-brown. and white. Upper parts : immediately above mantle an Primaries : outer vanes and tips dark sepia, ill-defined triangular area of brownish- inner vanes and quills buff, forming a grey with the apex towards the tail, finely broad wing-bar. vermiculated white and sepia. Long scapulars: dark brownish-sepia; Rump and rectrices : dark sepia. innermost obscurely vermiculated, those Flanks: pale brownish-grey, finely vermi­ adjacent to speculum reflecting dull green, culated pale sepia. then becoming grey. Wing: coverts dark grey, almost uniform, Underwing: white, fore edge mottled but quills darker with slight coppery- grey. purple reflections. Tips of greater wing- Measurements (in mm.) coverts at speculum broadly tipped sepia. Wing: 212 Speculum: white, broadly-edged grey and Bill: narrowly white, extending on to primaries. length from feather margin 44.5 Innermost secondaries strong grey. width at nostrils 19.5 Primaries : outer vanes and tips dark sepia, width at widest point 21 inner vanes and quills pale buff forming a nail 9.5 x 7.5 broad light wing-bar. Tarsus: 36 Long scapulars: uniform dark sepia, Middle toe without nail: 57 faintly reflecting purplish. 13. P o c h a r d A. ferina x F e r r u g in o u s Underwing: white, fore edge mottled D u c k A. nyroca,

AYTHYA HYBRIDS 55 Underwing: white, fore edge mottled the iris or soft parts in any of the above greyish. Pochard X Ferruginous Duck. Measurements (in mm.) 1 5 . T u f t e d D u c k A. fuligula x F e r ­ Wing: 212 r u g i n o u s D u c k A . nyroca, $ by plumage. Bill: ‘B a e r ’s P o c h a r d T y p e ’ . British Museum length from feather margin 43.5 Collection, Reg. No. 1858. ‘Zoo. Soc.’ width at nostrils 17 Crown, head and neck : crown dark width at widest point 19-75 coppery-red with a short crest which nail 10 X 8 hangs over nape. Cheeks are predominantly Tarsus: 39 dark green with slight coppery-red reflec­ Middle toe without nail: 57 tions; throat is generally dusky and there 14. P o c h a r d A . ferina x F e r r u g in o u s is a smallish white chin spot. Rest of neck D u c k A . nyroca, 3 imm. ‘P a g e t ’s presumably greenish, but hidden as P o c h a r d ’ or ‘F e r r u g in o u s T y p e ’. specimen is mounted with head down on December 8th, 1933. Heigham Sound, shoulders. Norfolk. (Lord Desborough Coll.) Norwich Note: Artificial eye pale orange-yellow; Castle Museum No. 66.934. bill has been coloured grey, the nail is Crown, head and neck : chestnut-red, crown blackish; this is almost certainly incorrect to nape slightly darker; a white chin- and it is more likely that the tip was spot present. blackish and that there was also some Breast: dark coppery-red; feathers broadly black at the base of the bill. edged ash. Upper parts: the mantle is nearest to Belly: white, feathers edged pale coppery- Ridgway’s Seal Brown (PI. Ill, No. 1). It red giving an irregular barred effect. is very finely and obscurely vermiculated Vent: grey, washed dilute coppery-red, fawn. Rest of the upper parts are similar, and faintly vermiculated white. although the upper tail-coverts are blacker. Under tail-coverts: proximal as vent; The rectrices are the same Seal Brown, distal ash-white, tipped pale coppery-red. reflecting a coppery sheen. Rump and upper tail-coverts: dark sepia, Under parts: the breast is a dark coppery reflecting coppery-red. red-brown, at the lower edge with some Rectrices: as rump (two outermost faded broad whitish fringes. Centre of breast juvenile, colour ash-brown). silvery-white, lower abdomen to vent Flanks: a mixture of greyish-white, ver­ washed pale reddish-brown, finely ver­ miculated pale sepia, and rather coarse miculated white. Under tail-coverts fulvous-brown and coppery-brown. whitish, mixed with paler reddish-brown, Upper parts : over shoulders and mantle a vermiculated palely, with a few feathers warm coppery-brown, paler at edges of tending to white. feathers. At shoulders coppery-red (rich Flanks: pale reddish-brown, slightly grey, by contrast). Colour of mantle forms a vermiculated white. broad U-shaped area, directed forwards. Rectrices: pale sepia. Wing: covens, brownish-grey, becoming Wing: (Note: a proper examination not greyer and broadly edged sepia at speculum. possible owing to the specimen being Speculum: white, at lower border becom­ mounted and fragile.) Upper wing-coverts ing grey merging into sepia, some of the appear a uniform Seal Brown becoming feathers minutely tipped white. darker at the speculum, which is white and Primaries : outer vanes and tips sepia, dark extends on to primaries. on tips; innermost paler, rest of feather a Primaries : sepia with darker tips and outer pinkish-buff forming a broad wing-bar. vanes. Scapulars: proximal dark grey, finely Scapulars: longest Seal Brown with outer vermiculated whitish; longest uniform vanes dull oily green; lower edge of warm coppery-brown, outer vanes dully speculum dark sepia; fore edge of wing reflecting green. warm brown mottled whitish. (Under sur­ Underwing: white, fore edge mottled grey. face of wings could not be examined.) Measurements (in mm.) The tarsi and feet have been crudely Wing: 201 coloured dark grey. Bill: Measurements (in mm.) length from feather margin 48.5 Wing: 214 width at nostrils 17 Bill: length from feather margin 47 width at widest point 20.5 width at nostrils 20 nail 10 X 7 width at widest point 22 Tarsus: 35-75 nail 10 X 8 Middle toe without nail: 50.5 Tarsus: 37 Note: There is no record of the colour of Middle toe without nail: 50.05

56 THE WILDFOWL TRUST Note: this specimen is disintegrating captivity all of the types of hybrid already rapidly. mentioned in this paper, and these are 16. Tufted Duck A. fuligula x F e r ­ now discussed under several headings with ruginous Duck A . nyroca (sex not special reference to their likeness to parent recorded). ‘Baer’s Pochard Type’. No or different species. For easy identification data. ‘Zoo. Soc.’ British Museum in the text the live birds are listed and Collection, Reg. No. 71.3.20.3. numbered in Table II, the numbering Crown, head and neck: crown dark following on that of the museum specimens. coppery-red, short dependent crest of 17. ‘Baer’s Pochard type’. (See Plates same colour; cheeks similar but less bright. 3, 4 , 50 Behind ear-coverts and at sides of nape In full plumage at close quarters, this strong dark irridescent green. Throat and bird was very much like a drake Baer’s front of neck dusky coppery-red and a Pochard. At a distance, however, and small white chin spot (neck has been especially when displaying, there was a shortened considerably in make of skin). strong superficial resemblance to a male Upper parts: shoulder regions dark Ring-necked Duck. This likeness to the coppery-red. latter was mainly due to its dark plumage Mantle: dark Seal Brown, very obscurely with lighter flanks and distinctly altered vermiculated fawn. head-shape when the crest feathers were Rump and upper tail-coverts : similar but elevated. Our side view photograph, taken uniform, the coverts being darker. in 1962, shows the ‘cut-off’ crest lying flat. Rectrices : dark sepia. It is of interest to record that this particular Under parts : breast dark chestnut-red, at bird was reported as a Ring-necked Duck lower edge with paler fringes to feathers. to the editors of British Birds in 1962. Breast: silvery-white. In eclipse plumage, its striking resem­ Belly and vent: warm brownish-grey, blance to a Ferruginous Duck was such as finely vermiculated white. to suggest that late summer and autumn Under tail-coverts : mostly white. records of that species require the closest Flanks: reddish-chestnut, pale, finely and scrutiny by those responsible for County obscurely vermiculated white, more uni­ or National records, and it may be advisable form towards tail. to review all past records of Ferruginous Wing: upper wing-coverts uniform Seal observed between July and October. In Brown, slightly paler than upper parts passing one may ponder on what the generally. juvenile drake of this type looks like. Speculum: white extending on to inner­ In full winter plumage the crown, fore­ most primaries giving a broad white wing- head and crest (tapered to a point), bar; fore edge of wing mottled warm brown appeared to have a purple-bronze sheen and white. quite distinct from the green sheen on the Primaries: sepia, tips and outer vanes rest of the head and neck. The side panels darker. appeared dusky with a white edging along Measurements (in mm.) the top and there was a small amount of Wing: 186 (tip worn) white on the under tail-coverts, especially Bill: length from feather margin 39 at the sides. These last two features can be width at nostrils 18.5 seen in our side view photograph. width at widest point 20.05 In eclipse, the plumage was brownish, nail 10 X 7.5 the sheen on the head and neck being Tarsus: 34.5 absent. The under tail-ooverts were whiter Middle toe without nail: 52.5 than earlier on (if, of course, it was the Note: bill still shows black tip and some same bird as the one present five months black at base. This latter bird was recorded before). Since some adult male Tufted by Sage (1962) together with a wild shot Duck acquire white under tail-coverts at female, thought to be of the same paren­ this season an increase of white would not tage (Van Oort 1908) from Nieuwkeep, be surprising. Holland, which we have not seen. The The eyes on all occasions were the palest illustration of this bird in Sage’s paper of yellow to white. Almost the same size as shows the dark flecking of the under parts, a Tufted Duck. bearing a remarkable resemblance to some On all occasions Tufted Duck were its female Ringed-necked Duck and variant associates, and each year it was commonly female Tufted Duck and Scaup (Harrison, a member of Tufted Duck courting parties. 1961 and 1962) in winter plumage. Pochard were always present on the lake, but it did not associate with them. Part Twos Live hybrids studied (See This bird was seen to make the ‘neck- Table II). stretch’ and ‘head-throw’ postures of the We have observed in the field or in Tufted Duck. The crest feathers were

AYTHYA HYBRIDS 57 Table IL Live Aythya hybrids observed by the authors, 1959-65

Ref. No. Type Where seen Date Photographs

17- ‘Baer’s Pochard type’ St. James’s Park, Mar.-April and 29 Aug. 4 , 5>6 3 London 1959; 27 April-4 May i960; i i Mar.-8 May 1961; 28 April-24 May 1962. Possibly the same bird each year 18. ‘Lesser Scaup type’ St. James’s Park, 21, 23, 25 Feb. and 11 3 London Mar. 1959

19. Two 3 3 > pinioned Slimbridge, Glos. Various dates in 1962 and 2 1963 20. 21.

22. 3 Leyboume, Kent 4 April 1964

23. 3 Sundridge, Kent 24-27 Feb; 16 N0V.-21 Dec. 1965 24. ‘Scaup type’ St. James’s Park, 9 Jan.-I5 Sept. i960 3 London 25. ‘Tufted Duck type’ Reykjavik, Iceland 9 May 1965 14 26. Two S 3 Sevenoaks, Kent In captivity 1958-1962 10 (specimen no. 6 & 7) 27. ‘Pochard type’ St. James’s Park, 27 Jan. 1962 3 London 28- ‘Ferruginous Duck type’ 30. Two 00, one $ Regent’s Park, London From 28 Nov. 1963 ; bred in park about two years previously. One pair full winged. 31.- 34- Two pairs Sevenoaks, Kent Bred by J. P. Williams, Pochard S x 1964, in captivity Ferruginous Duck $ 7 and 8

frequently elevated and the cheek feathers March 1963, was more reddish, while in fluffed out. The ‘hoi’ note like that of the April 1962, one of us noted it as orange. drake Tufted was heard. Early in September 1963, these two 18. ‘Lesser Scaup type’. birds were almost certainly in eclipse - a This bird was even more like a drake dull version of full plumage. A third bird, Lesser Scaup than the Sutton Courtenay which closely resembled them, was in the bird on account of the absence of black at same pen, its only apparent difference the base of the bill. Apart from this being a whitish line around the base of the difference it closely resembled the Sutton bill as in the male Ring-necked Duck. Courtenay bird, especially in lacking green This bird was probably the American reflections on the head and having a similar counterpart of our ‘Lesser Scaup type’. eye colour. It associated closely with The £head-throw’ display posture of the Tufted Ducks during its stay, though drake Tufted Duck was noted in April Pochard were present on the lake, 1962. ig and 20. ‘Lesser Scaup types.5 (See 21. ‘Lesser Scaup type.’ Plate 2.) " Closely resembled the Sutton Courtenay These two Wildfowl Trust birds were bird. Its eyes, however, were noted as light very much like other drake ‘Lesser Scaup brown. It was observed swimming with types’ but with one important difference. five Tufted Ducks though a party of At our request3 Dr. G. V. T. Matthews eight Pochard were on the lake. kindly studied their plumage over a period 22. ‘Lesser Scaup type.’ and noted a distinct green tinge towards Virtually identical to 21. There were the back of the head. Dr. Matthews also about 25 Tufted Ducks on the same water. comments on eye colour which was 23. ‘Lesser Scaup type.’ clearly changing with time. In December Also virtually identical to 21. This was 19623 it was chiome yellow, and early in the only hybrid of this type to associate

58 THE WILDFOWL TRUST with Pochard. At the time there were 65 neck were black with green reflections and Tufted and 83 Pochard on the water, but there was a minimal stubby crest. The the hybrid kept exclusively with the mantle and scapulars were grey with Pochard. coarse white vermiculations, the back being 24. ‘Scaup type.’ much darker than a drake Scaup. The This bird so closely resembled a drake flanks and belly were white, the upper Scaup that some observers refused to breast black. The wings, tail and tail- believe it was anything else! Similar coverts were dark sepia and the speculum hybrids have already been described (Sage, was white, extending on to the primaries. 1963), and the most important differences The bill was all blue with a black triangular between this bird and those described by tip and the iris pale yellow. Sage are (a) the rounded Scaup-like head Although both Scaup and Tufted Duck without any peaked appearance, (è) absence were present, it associated with neither of any purple reflections on the neck in full species; in fact it was frequently chased plumage. At all times this ‘rounded-head by drakes of both species and by Eiders. type’ presents an identification problem When the pond was revisited on 9th and to the un-critical, especially in juvenile 10th June it was not seen. plumage or in eclipse. Size as Scaup and General Comments Pochard. It was distinctly larger than any Tufted with heavier build and thicker neck. A bird which appeared in St. James’s Head-shape as Scaup without any suspicion Park, London, in 1942 was identified, and of a crest or kink. reported, as a Scaup, and its photograph Early in July this bird started its wing appeared in The Times. Of this bird moult which lasted for 32 days. Bannerman (1958) writes, ‘I saw the bird It associated exclusively with Tufted myself on several occasions . . . ’ and, Duck and on a number of occasions ‘. . . to everyone’s delight this, or another between 16th April and 26th May was in similar bird, turned up again in a succeed­ close attendance on individual female ing winter’. Through the courtesy of The Tufted Duck. Times we have obtained prints of their On 21 st May it was seen to adopt the photograph (see Plate 15), and in our ‘head-throw’ posture of a drake Tufted opinion it is clearly a ‘Scaup type’ hybrid Duck. closely resembling the bird No. 24. The 25. ‘Scaup type.’ (See Plate 14.) Tufted Duck-sized bill, definitely not a This drake was observed at close range character of the Scaup, is shown clearly in on a pond near Reykjavik airport in May the photograph. See also bill characters. 1965. In size it was intermediate between a In the Royal Parks Report* a Scaup was Scaup and a Tufted Duck. The head and reported in St. James’s Park every winter Main plumage points as follows : Full adult plumage (from 16 th April to Immature Plumage early August) Eclipse Head Brownish with patches Blackish with green gloss Dull dark brown with pale Colour of green sheen and a little mauve gloss on drooping crescent behind crown and forehead eye (as in female Pochard) and a whitish crescent on the cheeks Neck As head As head As head Colour Upper Rump and upper breast Upper parts blackish. Upper parts dull dark parts brown. Mantle and back Mantle and scapulars brown except for mantle brownish with greyish finely vermiculated and scapulars which were a odd patches of Scaup with blackish-brown. The little browner than earlier grey. Tail brown. markings were more like on. Tail brownish. those of a Lesser Scaup than a Scaup. Tail blackish. Flanks Brownish with some white White, as a drake Tufted Pale brownish-grey. showing along waterline. Duck. Under Upper breast brown Upper breast blackish no Upper breast dull dark parts motded black. Under green gloss. Under tail- brown with some black tail-coverts brown. coverts black. Rest of under markings. Under tail- parts white. coverts dark brown. Wings Wing bar similar to drake Tufted Duck. Primaries were noticeably short, the wing tips just meeting when bird was on water. Eye Pale yellow. Pale yellow. Pale yellow. 1 by Committee on bird sancturies in Royal Parks ().

AYTHYA HYBRIDS 59 from 1939 to 1946, whereas in a subsequent It was seen among a group of 30 Tufted period of ix years covering the time of Ducks, though Pochard were present on hybrid notoriety, only hybrids have been the lake. reported. In view of this we suggest that past records of single Scaup in Inner General Comments London might well be reviewed. Our translation of Bezzel’s (i960) paper 26. ‘Tufted Duck type.’ (See Plate 10.) indicates that most hybrids at Ismaning The general posture and appearance of were ‘Pochard types’, i.e. like the specimen these birds was that of a drake Tufted from his collection which we ourselves Duck, in some ways rather like some drake have examined (our ref. No. 3). Perrins Tufted Ducks in post-breeding moult. In (1961) however, remarks that Bezzel’s its eclipse plumage this type of hybrid descriptions differ little from the Sutton would be virtually indistinguishable in the Courtenay specimen, which is somewhat field from an eclipse drake Tufted Duck. confusing, and due, no doubt, to Perrins The head had the full rounded appear­ not having examined the Bezzel skin. ance of a Tufted drake, whereas the 28/29/30. ‘Ferruginous Duck type’ (See Pochard tends to have a more sloping Plates 7 & 8). forehead. The neck was noticeably thinner The drake hybrid of this type bears a than a Pochard and was much like that of a strong superficial resemblance to a male Tufted Duck. In eclipse the crest was Ferruginous Duck and it is only on the totally lost and the whole of the head, finer points of detail that it can be dis­ neck and breast became a dark sepia- tinguished in the field. Size as drake brown. The fine vermiculations were lost Ferruginous and drake Tufted Duck, but on the mantle and this became browner. head and body shape as a drake Common The belly remained very much as it was in Pochard. Head, neck and breast are the full plumage. The flanks became browner Pochard’s rather than the Ferruginous’ and lost their vermiculations. There was rich chestnut with some black feathers on no significant change in iris or bill colour. the forehead (as in the Pochard) and on The former at all seasons was pale the upper breast. Tail and wings a medium yellowish-brown. grey-brown, not so dark and rich as in the Our photograph, taken in February Ferruginous. Flanks similar to wings but 1962, shows the flanks somewhat lighter much paler and the tail-coverts a darker than in life. The short, well-defined crest brown than the wings. One of the drakes is clearly to be seen. had a little white on the under tail-coverts The ‘head-throw’ posture of the drake just below the tail but this was not Tufted Duck was seen on many occasions. apparent in the second drake. Belly 27. ‘Pochard type.’ appeared silvery-white sharply demarcated O f all the hybrid types we have studied from the chestnut breast. A broad white in life, this bird, although seen well, did wing bar extended on to the primaries as not come under such close observation as in the Ferruginous. The eyes were orange the others. It was present only on one day, and the bill similar to a male Pochard— during which it remained some twenty quite distinctive from the male Ferrugi­ yards off-shore. It looked more like a nous (ef. bill sketches). Pochard drake than a Lesser Scaup drake In eclipse it was more difficult to separate in colour and pattern, but its thinner neck, from the drake Ferruginous as among the very short loose crest, and absence of black differences the eyes were paler, and the at tiie base of the bill, set it apart from the under tail-coverts whiter, than earlier on former species. Body size as a drake (but under tail not as brilliantly white as in Tufted Duck or perhaps a trifle larger, but drake and duck Ferruginous at the same longer in the neck; head-shape also recalled time of year). The head was similar to an a Tufted Duck because it was more old drake in eclipse and rounded and with a short loose crest. The the flanks and wings still lacked the rich­ latter was visible when the bird was alert ness of colour of the drake Ferruginous or dozing. Head colour a dull dark brown though this contrast was less obvious than with a copper tinge. That part of dorsal in full plumage. (See Plate 8.) area and wings visible when the bird was The ‘head-throw’ posture of the drake resting on water was a mousy-grey, Pochard was given by both drakes (less similar to the ‘Lesser Scaup type’. Upper quick than in the drake Tufted Duck). A breast blackish-brown, not as black as in second posture, the ‘neck-stretch’, was the male Tufted Duck. Flanks whitish, but like that given by drakes of both Pochard not as white as in the drake Tufted Duck and Ferruginous, as was a third posture, and recalling the side panels of the ‘Lesser in which the head and neck was extended Scaup type’. Stem end black as in drake flat along the surface. This last is not Pochard. characteristic of drake Tufted Ducks.

60 THE WILDFOWL TRUST Adult female: the 20 records, 7 appear to us as perfectly The separation of this bird from the satisfactory Ferruginous Ducks, 10 have duck Ferruginous in the field presents an too few details (or none at all) upon which even greater problem; in fact at any dis­ judgment can be passed, while 3 are tance over fifty feet there could be no unsatisfactory since the birds are not certainty unless a duck Ferruginous was clearly separable from Paget’s Pochard. on hand for detailed comparison. Concerning descriptions of some Ferrugi­ In general colour, the likeness to a duck nous seen in 1950-51, the editors of British Ferruginous was close, but the loral area Birds say (vol. X LIV , p. 352) ‘the white and cheeks were less rich. The breast and eyes of the drakes did not always show up flanks were a dusky chestnut brown, again as conspicuously as might be expected’, a less rich than in the Ferruginous. Wings, statement which causes us some mis­ tail-coverts and tail dusky brown with a givings. As we have expressed elsewhere, a faint grey tinge and a small amount of white reappraisal of Ferruginous Duck records is was visible just below the tail. Bill colour not untimely if the high standards of and shape similar to a duck Pochard. The British ornithology are to be maintained. head was a little more rounded than in In addition to the specimens we have that species, a character particularly examined (Nos. 11-14) and the recent noticeable when the two were side by side. sight records we know of another sight Size only a trifle smaller than a duck record in 1936 (Harrison 1953) making six Pochard and as big as, if not slightly larger occurrences at intervals in the past 65 than, the male hybrid of this type. years.* In wing moult the duck hybrid still The two pairs bred by Jack Williams in closely resembled the duck Ferruginous, 1964, three of which are now at Sevenoaks both having almost pinky chestnut fore­ (Plate 7) are virtually identical with the heads. Apart from the duck Ferruginous’ above. more conspicuous white under tail-coverts the only obvious differences were : (a) body Variable characters ira the and head shape of the duck hybrid re­ Aythya hybrids sembled a Pochard, whereas the Ferrugi­ In general, all six types of hybrid described nous was more like a Tufted Duck; (è) the tend to be intermediate in character duck hybrid was nearer a duck Pochard in between their parent species. Only the size whereas the duck Ferruginous ap­ ‘Tufted Duck type’ shows a character not proached a duck Tufted in build. present in either parent in winter, that is the dark under parts, which are darker General Comments than could be expected if this was referrable The drake hybrid is sufficiently well to a Pochard character. The probable known in British ornithology to have explanation of this is that it is a reversionary acquired the name of Paget’s Pochard and character revealed by the hybridisation, as one cannot help feeling that if the editors has been strikingly demonstrated in the of British Birds had brought the Paget’s bimaculated face pattern of Wigeon Anas Pochard problem to the notice of their penelope Linnaeus X Teal A. crecca readers, the ‘Lesser Scaup problem’ as Linnaeus and Wigeon X Shoveler A. such might never have existed, or, at any clypeata Linnaeus hybrids (Harrison 1954 rate, might not have dragged on for so long. In reviewing their handling of * A drake Paget’s Pochard was identified on a Ferruginous Duck records since the last gravel pit near Dungeness, Kent, on 16th war, one gets the impression that Paget’s October, 1965, by P.. E. Scott. It was smaller Pochard never existed! Warnings concern­ than the accompanying eight Tufted Duck ing the acceptance of sight records of and female Pochard. The body plumage in Ferruginous Ducks in these islands given sunlight was reminiscent of a Ferruginous by the editors of British Birds dwell on Duck with reddish head and back, which showed little or no contrast. The flanks were a such points as justification for believing uniform smooth dark grey. The white under birds to be genuine immigrants because tail-coverts were conspicuous in the rear view few were kept in captivity (about 1949-50) with the tail raised, otherwise indistinct and and caution over identification because sometimes not visible on side view with tail some duck Tufted have prominent white depressed. under tail-coverts. Our examination of The eye colour was as a drake Tufted Duck— eight issues of British Birds giving some perhaps a little less yellow— certainly not white. 20 records of Ferruginous observed The beak was sketched in the field and was between April 1947 and October 1951 typical of Paget’s Pochard, as shown in our sketch. failed to produce any reference to the This record gives further support to our possibility of confusing this species with views on Ferruginous Duck, if the records are the hybrids known as Paget’s Pochard. Of to be put right.

AYTHYA HYBRIDS 61 and 1964). In this case, the dark under glossed head, a kink at the back of the parts are probably reversionary towards head, white flanks and bright yellow eyes other dark-bellied Aythya species. (from notes of R. Giilmor). The remarkably different morphology, Sage (1963) considers that the ‘Lesser according to the direction of the cross in Scaup type’ hybrid lacks the green gloss Pochard and Tufted Duck hybrids has of the ‘Scaup type’ and that it always has a already been referred to (see specimens 6 black base to the bill. However, in our and 7). One has now to consider the ‘Lesser opinion these characters are variable: Scaup type’ hybrids in comparison with the (a) there may or may not be some green ‘Pochard type.’ tinge or gloss on the head. We have no knowledge of the parentage (b) there may or may not be any black at of the ‘Pochard type’ hybrids described, the base of the bill. but in general, the external morphology is A bird at Barn Elms, Surrey, in February similar to the ‘Lesser Scaup type’ hybrids, 1958, had a purple head-gloss, a distinct the main difference being the much kink at the back of the head, no black at brighter, more drake Pochard-like coloura­ the base of the bill and yellow eyes (from tion. We think that these two types of notes by P. Fullager). hybrid will prove to be individual varia­ One of the curious features about the tions originating from the same cross, but Aythya hybrids described is their resem­ possibly the ‘Pochard type’ might be the blance to the six different species of the result of back breeding with Pochard genus, of which the ‘Lesser Scaup’ type predominance. In due course this should presented a sufficient problem to deceive be solved by hand-reared hybrids of several experts, and for one of the latter to known parentage. produce meteorological evidence in sup­ In this respect, it is noteworthy that port of a transatlantic drift in explanation ! Bezzel (i960) mentions a surplus of duck Perhaps the most striking of the hybrids Pochard and drake Tufted Duck at is the Ferruginous X Tufted Duck, result­ Ismaning in April, suggesting that this is ing in the ‘Baer’s Pochard type’, resembling the time when pairing may occur between Aythya baeri (Radde), a far eastern species. the species. The same conditions apply at With this in mind, the possibility that St. James’s Park, but there has only been some of these species may have arisen by one instance of mixed pairing here, reticulate evolution is worthy of con­ during 12 years of intensive observation. sideration. It may be that geographical differences in Mayr (1942) stated ‘Reticulate evolution the breeding season of the two species is possible only where different species, may give rise to a zone where the breeding genera and families can hybridize success­ seasons of the two species coincide, thus fully, and this occurs only exceptionally in favouring hybridisation. The pair involved . . .’ was a drake Tufted and duck Pochard. Doubtless spéciation can arise as a result Sage (1963) considers that Scaup X of inter-specific hybridization, but it is Tufted Duck hybrids show fairly con­ evident that this process must, and no stant characters. However, while they doubt does, take aeons of time to establish seem to be more Scaup-like in size com­ a new species. pared with the slightly smaller ‘Lesser Most of the are very fertile Scaup types’ the following appear variable: inter se and for spéciation to result from (a) head may be either distinctly peaked or hybridization it is essential for some rounded in shape. additional isolating factor, either biological (þ) head and neck may have either a or ecological to operate in favour of any predominantly green gloss or a pre­ particular inter-specific cross, otherwise dominantly purple gloss. constant gene dilution would effectively The flanks and belly of all specimens of prevent or delay spéciation arising. this type referred to herein, are whiter than in the ‘Lesser Scaup type’, a difference Bill coîîîparisoiîs of some not stressed by Sage (1963). Aythya hybrids A two-year old bird of this type observed In his interesting paper Perrins (1961) on an ornamental water at St. Neot’s, stresses the diagnostic bill pattern of the Hunts., on 24th May, 1958, had white Sutton Courtenay bird and gives sketches flanks, a purple-black head with a green comparing its bill markings with those of sheen over a very wide area; a distinct drake Lesser and Common Scaup, Tufted kink at the back of the head and lemon Duck and Pochard. This key to identifica­ yellow eyes (from notes by B. Rose, sent tion would have been valuable if the to us by British Birds). A similar bird at sketches of the last two species had been Theale, Berks., in February and March both accurate and typical. Neither of the i960, also appears to have had a green sketches of the bills of Tufted Duck and

62 THE WILDFOWL TRUST Pochard are like those figured in The written to warn observers of the identifica­ Handbook of British Birds, vol. Ill, tion problems posed by certain known pp. 301 and 292 (a fact not alluded to by Aythya hybrids, because even orni­ the author), and it is extremely doubtful if thologists with previous experience of an adult drake Tufted Duck in full winter both Scaup and Lesser Scaup have been plumage ever has a bill tip like Perrins’ misled by hybrids of these types. One drawing in British Birds 54:51. To focus expert who saw both the Sutton Courtenay attention on the importance of bill charac­ and the St. James’s Park ‘Lesser Scaup ters we have reproduced both Perrins’ and types’ and who was warned of this hybrid’s The Handbook’s sketches alongside our own diagnostic bill tip, still maintained that diagrams relating to various hybrids, in both were genuine Lesser Scaup. It is all particular those observed in life (Figure 1). too easy for observers with many years Based on our material the bill tips of experience to talk themselves into wrong adult drakes in full plumage of five species identifications. and six types of hybrid may, generally It seems that in the case of the Sutton speaking, be divided into three distinct Courtenay bird, the weight of opinion was groups as follows: in favour of a Lesser Scaup rather than a (Note: The letter preceding each species hybrid, which was symptomatic of the or type is the reference to our diagrams.) rarity hunter outlook. In our opinion the Crescent or ‘Mr. Moon’ -shape black bill Nature Conservancy were entirely right tips. to issue the licence to collect the Sutton Courtenay bird, but some of the confusion (¿, j, k, I, m) ‘Lesser Scaup type’ (with or and uncertainty over this and similar without black at base). birds referred to by Nicholson (1961) (0) ‘Tufted type’ (no black at base). could have been resolved had the bill (n) ‘Pochard type’ (the St. James’s Park characteristics been better understood. bird had no black at base). (/3 g> h) Common Pochard (also extensive As knowledge on Aythya hybrids accu­ black at base. The light area on the bill is mulates, it is clear that a number of their sometimes noticeably enclosed by black field characters are variable, so that no through black edges of the bill joining the identification key could be relied upon to black base to the black tip. ef. Figure i). separate them from the species they closely (p) ‘Ferruginous Duck type’ (with dusky resemble. We feel that for the time being basal J of bill). the following precautions should be observed : Fan - or inverted cone-shaped bill tips. (q, r) ‘Scaup type’ (black extending over 1. No sight record of a Lesser Scaup the nail a little way and no black at base). should be admitted to the British List, (s) ‘Baer’s Pochard type’ (black extending unless it is a fully adult male showing a little way over the nail and, apart from a every field characteristic of the species and pale area just behind nail, rest of bill seen for a long period at close quarters and dusky, ef. Plate 3). confirmed by several waterfowl experts. (d) Tufted Duck (black extending over nail The same should apply to Ring-necked and no black at base). Duck records. In the above three the black is confined to the extreme tip and does not extend so far 2. More caution should be exercised round the edges of the bill as in those with over the acceptance of Ferruginous Duck crescent-shaped bill tips. sight records. Only fully adult drakes (e) Ferruginous Duck (dusky area over showing all field characters should be dealt basal f of bill. The bill of the ‘Baer’s with on a county basis. Females and males Pochard types’ closely resembles the in other plumages should be considered by Ferruginous Duck’s). experts. Small irregular-shaped or finger-nail shaped 3. Single adult Scaup among Tufted black circlet on bill tip. Duck and Pochard flocks well inland, (a) Lesser Scaup 'I Black on bill tip con- where the Scaup is always a rare visitor, (1b) Scaup f fined to actual nail and should be treated with suspicion and should J no black at base. be confirmed by experts. Immature Scaup Note: rarely, a drake Tufted Duck may in such localities are essentially an expert’s have the black confined almost wholly to province. the nail, recalling a Scaup. This paper shows the value of co-opera­ tion between the museum worker, the Cosiclusioias wildfowler, the field observer, the photo­ At the present time too much cannot be grapher and the aviculturalist.

AYTHYA HYBRIDS 63 AYÏHYA BILL CHARACTERS SPECIES

V\ a / ' AA/ VvV Y\Ar * 9 « i %

& X êJ

w g ,U M HYBRID TYPES \

« (7 I 9 % 9 u u u .u .u

w

64 THE WILDFOWL TRUST Figure i. Key to diagram of Aythya bill characters: Species: (a) Lesser Scaup; (b) Scaup; (c) Tufted Duck (after Perrins, see note i); (cl) Tufted Duck (after Handbook, and from life); (e) Ferruginous Duck (from life); (/) Pochard (from life); (g) Pochard (after Handbook, and from life); (h) Pochard (after Perrins, see note 2). Hybrid types: (i-m) ‘Lesser Scaup type’ ; (i) Sutton Courtenay (after Perrins, see note 3) ; (j) Sutton Courtenay (from skin and photograph in British Birds); (k) St. James’s Park bird; (I) a Wildfowl Trust bird, April, 1962; (m) a Wildfowl Trust bird, March, 1963 (after Matthews). (n) ‘Pochard type’ Bezzel’s skin (tip only of bill); (0) ‘Tufted Duck type’ Harrison’s bird (from life); (p) ‘Ferruginous Duck type’ Regent’s Park and Harrison’s birds (from Ufe); (q) ‘Scaup type’ St. James’s Park bird (from life, and photograph); (r) ‘Scaup type’ Sage’s bird (tip only from photograph in British Birds); (s) ‘Baer’s Pochard type’ St. James’s Park (from life). Notes 1. Tufted Duck (c): in spite of close examination of over 1,000 adult drakes in full plumage, we cannot substantiate this type of bill tip in the Tufted Duck. 2. Pochard (h) : this type of bill tip in adult drake Pochard in full plumage is unknown to us in spite of close examination of about 100 adult drakes. 3. ‘Lesser Scaup type’ (i): questionable whether tip is accurate.

Acknowledgements We gratefully acknowledge the help we Mr. A. May; Mr. S. E. Pratten; Mr. have received from a number of different Bryan Sage; Mr. R. E. Scott; Mr. R. people and institutions in compiling this Smith; Professor Dr. K . H. Voous of the paper: Miss Ruth Barnes of the Norwich Zoological Department of the University Museum; Dr. Bruce Campbell; Dr. G. of Amsterdam; and Mr. J. P. Williams. Diesselhorst of the Munich Natural We are also grateful to the editor of History Museum; Mr. I. J. Ferguson-Lees, The Times for permission to reproduce the Executive Editor of British Birds; Mr. E. photograph of the supposed Scaup in Fielder; Mr. C. J. O. Harrison; Mr. St. James’s Park and we would like to make P. A. D. Hollom; Mr. C. D. Jolly; Mr. a special acknowledgement of our gratitude Terry Jones; Mr. J. D. Macdonald of the to Dr. Pamela Harrison for the majority of British Museum (Natural History); Dr. the photographs, which add so much to G. V. T. Matthews of the Wildfowl Trust; the value of this paper.

References

BEZZEL, E. i960. Beobachtungen an Wildlebenden Bastarden Tafel X Reiherente (Aythya ferina X A. fuligula). J. Orn. 101:276-81. D e la c o u r , j. 1956. The Waterfowl of the World. Vol. II. Country Life, London. h a r r is o n , c. J. o. 1963. The post-ocular green stripe as a plumage character in the Anatidae. Bull. B.O.C. 83:15-20. h a r r is o n , jam es M. 1953- The Birds of Kent. Vol. I. Witherby, London. harrison, james m. 1954. Further instances of aberrations of pattern in the Anatidae. Bull B.O.C. 74:52-3. harrison, james m. 1964. Further comments on hybrids between the European Wigeon and Northern Shoveler. Bull. B.O.C. 84:30-9. h a r r is o n , jam es M. and j e f f e r y G. h a r r is o n 1961. Variant winter plumage of the female Tufted Duck. Bull. B.O.C. 81:103-04. harrison, james M. and j e f f e r y G. h a r r is o n 1962. Variant winter plumages in the Scaup. Bull. B.O.C. 82:43. m a y r, e. 1942. Systematics and the Origin of the Species. Columbia U.P., New York. NICHOLSON, E. M. 1961. The ‘Lesser Scaup’ affair. British Birds 54:169. p e r r in s , c. M. 1961. The ‘Lesser Scaup’ problem. British Birds 54:49-54. ridgway, r. 1886. Nomenclature of colors. Boston. r iv ie r e , B. B. 1930. A History of the Birds of Norfolk. s a g e , B. L. 1962. Notes on some Ferruginous White-eye x Tufted Duck hybrids. Bull. B.O.C. 82:55-60. SAGE, B. L. 1963. Notes on Scaup X Tufted Duck hybrids. British Birds 56:22-7. v a n o o r t , E. D. 1908. Contribution to our knowledge of the Avifauna of the Netherlands. Notes Leyden Mus. 30:129-314. VOOUS, K. H. 1955. Hybrids of Scaup Duck and Tufted Duck. Ardea 43:284-6. ZOOLOGIST. 1909. Ornithological Report.

AYTHYA HYBRIDS 65