474 Mr. A. Brooks on the AJgnities of some [Ibis,

XXTV.-The Aflnities o j some Nearctic and Pabearctic Ducks. By ALLAN BROOKS, C.M.B.O.U.

(Text-figure 7.)

THE practice of uniting under a common specific name species that have hitherto been regarded as distinct, due to the fact that their respective ranges are widely separated geographically, often on separate continents, seems at the present time to be steadily gaining ground.

Such species (or subspecies) have obviously had a coninion rootstock a t a comparatively recent period, and the logical result is to regard them as conspecific, even if entirely separated geographically at the present day. But that the most enthusiastic advocates of this principle can carry it too far and so jeopardize the hoped-for unity of a iiniversal nonnenclature, is well illustrated by the different coiicepts of the statns of certain species of Ducks which QCCW on each side of the Atlantic.

The Redhead (JGJroca mzericana) is now being treated as a siibspecies of the Old World Pochard (Nyroca f t ~ i m z ) by European ornithologists. This theory can only have originated from a very superficial comparison of the two species, if an actual comparison was made at all.

I nm well aware that the i dea of their specific identity goes a long way back-at Ieast as far as William Mac- gilli$rap, but in the case of this usually careful naturalist it was obviously due to lack oE adequate material, as well as a very slight acquaintance with either species.

Between the years 1914 and 1919 there was an excellent opportunity to study the two species togethcr in life at the London Zoologicill Gardens. To one already well acquainted with the American ducks in life, the dissimilarity of theso two, Redhead and Pochard, was striking, together with the extraordinary resemblance of the latter to the American Canvasback ; in life the Pochard looks almost exactly like a sinall edition of that famous duck, both in the male and

'924.1 Nearctic and Palearctic Bucks. 475

female, especially the latter, and it would be quite as reasonable to regird it as conspecific with valisneria as with am&ana.

Ilhe following table gives the main points of resemblance anc. divergence between the three species (see also text- figure 7) :-

I Colourof back and Vermiculated,

' I

1

americana. ' vatdsneria. farina.

black. As in walis-

----l------l

Bill, colour in d. ! Black. 1 Black, with a sub, terminal bar of 1 bluish.

I

Bill, angle a t base.' Acute.

Iria, _..... ...... Orange to red. Red (YarreU).

1 Very acute. __------.

,: 9 , , . . . . . . . . . , / Dark vandyke I--- , Vandyke brown.

I brown. I

- ~ - - Bluish, with tip

and a narrow line a t base black, and with a subterminal bar of white.

Nearly square.

Yellow. Light yellowish

brown.

Face red; red confined to head and extreme upper neck.

Crown - feathers forminga bushy crest. --

Gray, very finely vermicnlated with bleak.

Uniform in colour with breast and shoulders, and only veryfaintly vermiculated.

Other points might be enumerated, but from the above it is obvious that the Old World Pochard is a good connecting- link between the two American species, with a slightly closer remmblance to the Canvasback ; in size, however, i t is smaller than either of the others.

'Cheories are futile, but the evidence might point to fere'na as being the common ancestor of the other two. T am well

476 011 some ilearetic aiid Palearctic Ducks. [Ibis,

aware that an effort is being made in America to re-establish the futile genus Aristonetta for the Canvasbacli. I only hope that nothing will lead the arbitrary arbiters of our nomen- clature to propose a new genus for the Redhead, though such a proceeding is just as wxrrantable as their separation of the Ring-necked Dock in a genus of its own. The Ring- neck (iVyroca collaris) is fa r more closely allied to the Redhead than the Redhead is t o the Pochard.

Test-fignre 7.

Bills of :-I. Nyrocn nmeiieunn. 2. N.,fe&a. 3. N . valisneria.

Another species that has been debased to a subspecies by English ornithologists is the American Green-winged Teal (.411as carolinensis). Here, again, there is no valid reason ; the white shoulder crescent of the inale carobinensis is a thoroughly qualitative character, and there are many other points of diwrgence. Also, there has never been an inter- mediate taken combining the characters of the males of the

Hoatzin perched on a bare branch.

Mucka-mucka on Canje Creek. YiTTV & SEABORNE LTD.

LONDON.

Ibis. 1 9 2 4 . PI. XXV

Berbice River with Banduri Pimpler.

Hoatzin in Banduri Pimpler trees. Y TTY & SEABORNC LTD

LO NO0 N .

1924,J On the Uoatzin in Rlitish Giiium. 477

two species, crecca and carolinemis. That the females are extraordinarily close is absolutely 110 justification for uniting the two.

The females of Anus tliscors and iliaus cyaizoptera are just as close ; in fact, there is at present no reliable character that will always separate the females of these two very distinct species, while the whitening of the wing-bar in creccci: towards its outer edge, as pointed out by Phillips (A Natural History of the Ducks, vol. ii. p. 232), will serve to separate nearly all, if not all, of the females of crecca and caroknense.

So while it is possible to agree to the uuification of species widely separated geographically, but the affinities of which are indicated by the occasional reversion of one to the type of the other, let us keep separate such ent,irely distinct bird-nnita as the Ducks here discussed. Uniting such specii’ically can serve no purpose whatever, not even the possible masking of the obvious resemblance to other closely- related races-as in the so-called European representatives of Pmthestes (i. e. Parics) atvicapilltis.

XXV.-iXotes on the Hoatzin in British Guiana. By M. D. HAYILAND (Mrs. H. H. BRINDLEY), M.R.O.U.

(Plates XXIV. & XXV.)

IN October 1922, while staying at Georgetown, British Guiana, I visited New Amsterdam, on the Berbice River, in search of Hontzins (Opistlcccornus Aoazin).

New Amsterdam, about fifty miles from Georgetown, is served by a railway whose express takes four hoiirs to cove11’ the dist:rnce. The line runs a t first through rice-fields and swampy grazing lands, transectetl by dykes ; these are fre- querrtly overgrown with the pink Lotus of the Nile, which has been introduced from the Old World. These dykes were full oE purple gallinules and jacanas, arid purple herons and