Page:The Zoologist, 4th series, vol 6 (1902).djvu/435

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COLOURING OF STERCORARIUS CREPIDATUS.
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(3) Another bird is much like this last one (No. 2), but there is, here, a distinct broad dunnish space dividing the throat and breast parts.

(4) Another bird—one of two standing together—is the common form (that is, dark), except that the neck and throat just below the head for about an inch is very much lighter, making a considerable approach to cream, without quite obtaining it. This light part is conspicuous in the one bird, but not in the other (No. 5) it is standing by.

(5) This other one might pass for the ordinary dark form, but on examining it through the glasses a lighter, though less salient, collar is distinctly visible.

(6) In a third bird, not far off these two (Nos. 4 and 5), the whole colouring from immediately below the forehead and crown of the head, which seems always to be black (or very dark), is of a uniform brown-drab or brown-dun colour, there being not the slightest approach to a lighter collar, or any lightness elsewhere, except that which—as in all the birds—becomes visible on the quill-feathers of the wings in flight.

(7) In another bird the breast and ventral surface is of a delicate silvery cream or creamy silver, something like that of the Great Crested Grebe. On the sides of the neck and just below the chin it is the same—perhaps a little less silvered; but between these two spaces—and so between the chin and breast—a zone of faint brown or dun, somewhat broken and cloudy, pushes itself forward from the wings, thus breaking the continuity of the light surface by the strengthening of a tendency which is, perhaps, just traceable even in the lightest specimens. Besides this a similar clouded space is continued downwards from the back of the head, first in a diminishing quantity, and then again broadening out till it joins the upper body-colour. So that here only a little of the nape is white, hardly more than what may be described as the two sides of the neck. This is a very pretty and delicate combination.

(8) Close beside this last bird (No. 7) is a uniformly dark brown one; and

(9), not far on the other side of it, one which exhibits the same sort of general effect, in a dark smoky dun. This latter bird would generally pass as representing the dark form, and,