The Zoologist/4th series, vol 6 (1902)/Issue 735/On the specific validity of ''Anser gambeli'' (Hartlaub), and its Position as a British Bird
ON THE SPECIFIC VALIDITY OF ANSER GAMBELI
(Hartlaub), AND ITS POSITION AS A BRITISH
BIRD.
By F. Coburn.
Fully realising the great importance which attaches to the introduction of a new species of bird to the lists not only of Great Britain, but Europe as well, I have not committed myself to the following observations and conclusions without mature study, and shall treat the subject with a minuteness of detail befitting its character.
At the meeting of the British Ornithologists' Club in October, 1901, when I exhibited a series of my Icelandic birds, I also submitted my specimen of Anser erythropus (ante, 1901, page 317), and an almost completely black-breasted example of what I then thought was A. albifrons.
In my collection I have another specimen of this stage, which I secured from Co. Mayo many years back, and which has the whole under parts much blacker even than the former one, being a glossy jet-black, practically without any admixture of drab.
Both birds had been a puzzle since they came into my possession, and this largely influenced me in taking my specimen to London with A. erythropus, as I expected to find similar birds at South Kensington, and thus receive enlightenment. I was, however, much surprised to hear from the courteous authorities at the Museum that they had never before seen a specimen like mine! and that A. albifrons was not known to assume entirely black under parts. It was vaguely suggested that my specimen might be A. gambeli!
Subsequently, at the request of Mr. J.H. Gurney, I sent A. erythropus and this black-breasted bird for his inspection, also to be exhibited before the Norwich Naturalists' Society. Mr. Gurney expressed to me his opinion that this black-breasted bird might be A. gambeli, and has since published this view in the able article, "On Anser erythropus and its Allies," in the current issue of the 'Ibis' (cf. 'Ibis,' 1902, pp. 269–275[1]).
On studying this subject later, I found that there was much diversity of opinion amongst authorities as to the specific validity of Anser gambeli, the bird having been separated from A. albifrons, and so named by Hartlaub as far back as 1852; and, although his diagnosis has been questioned by several ornithologists, there appears to have been no real effort made to settle the point during all these fifty years.
I must confess that when I first examined the series of skins at South Kensington I was much puzzled, and felt that, with such a series, it would be extremely difficult to discriminate between the two species. I may here say that I consider the series in the National Collection to be inadequate and not a representative one, there being but very few specimens, mostly, if not all, in the winter condition of plumage. Although I have examined the series of both birds twice, they have afforded me very little assistance.
Later, I got together my entire series of White-fronted Geese, and have devoted the bulk of the past winter season to a study of this subject. I have been lucky in securing many examples to fill gaps in my series, and have now sixteen carefully selected specimens to work upon, these providing ample material in my judgment for proving two important facts, viz. the specific validity of A. gambeli—it must not be regarded as a subspecies—and its frequent occurrence as a British bird; the whole of my sixteen specimens of the two species having been received from the west coast of Ireland at different times.
Most authorities agree that the chief distinguishing characteristics between A. albifrons and A. gambeli are, the larger and heavier bill, and darker under parts of the latter. I have found other characters which I will state later; but, taking this longer, broader, and generally heavier-built bill as my guide, I could easily separate the two birds, and make a series of ten A. gambeli and six A. albifrons.
Unfortunately, I lack some of the connecting links in the latter bird; I have seen them in years past, and remember them well, but did not secure them, not knowing at the time that I was collecting two species of birds. I shall meet with those connecting links later, and probably next season. One reason why my series of A. gambeli is so much more perfect than that of A. albifrons arises from the fact that, out of the great numbers of White-fronted Geese which have come under my notice, I have been in the habit, fortunately, of selecting only striking-looking birds, leaving the ordinary run to be secured at any time.
I shall now endeavour to show that these large-billed, heavily barred, or striking-looking immature birds should all be regarded as specimens of A. gambeli.
This series of ten specimens is a singularly, and I may say valuably complete one, ranging from the first plumage, through almost every grade, up to the breeding bird with glossy black under parts.
Now, it is in the two extremes—the immature and breeding stages—that it is most easy to discriminate between the two species, so far as plumage goes; in the intermediate or winter stage it is more difficult, as the student has then to rely mainly upon the differences in the size of the bill, a slightly longer tarsus, and, as my series shows, the distinctly lighter colour of the extreme outer wing coverts; this latter runs practically through the whole series, but perhaps too much importance must not be attached to it. There is another, and I consider very important osteological character, which I have discovered, and which cannot be detected unless the bird is in the flesh, but this I shall refer to in its proper place.
I believe that this similarity in the winter plumages of the two species—the stage most readily procurable by collectors—and the fact that there is no full, or in any way complete description published of the immature, or breeding stages, has led to much confusion, and caused the bird not only to be overlooked as a British species, but its specific validity to be doubted.
Because large-billed specimens have been procured in Great Britain, it has been concluded that they must belong to A. albifrons, and therefore that this bird has sometimes a bill quite as large as A. gambeli. If those British-killed, large-billed specimens in various collections were admitted, as they should, to be A. gambeli, much confusion would have been avoided.
My series demonstrates clearly the very important fact that the immature conditions of the plumage in A. gambeli are quite distinct from the same stages of A. albifrons; and, as I have before said, I can find no proper description of these stages, it will be necessary in proving my case to publish a full but brief description of these and the other leading features in my two series of birds. I ought perhaps to say that the stock of books available to me here is limited—I particularly lack American works—and I should like it to be understood that I do not positively assert that no proper description of these stages of plumage has ever been published, but that I cannot find any.
The immature plumage of any of the Wild Geese may always be known by the small size of the feathers clothing the body; in first plumage the feathers are not half the size of those of an adult bird. The feathers gradually increase in size as the bird advances towards January and February. With the growth of these feathers there is a change in the colouring matter, independently of a moult. But when the black feathers begin to appear on the breast, they are frequently, but not always, newly moulted feathers. I have plenty of evidence showing the black colouring matter being transmitted into drab feathers; indeed, this deposition of the black pigment goes on slowly until the whole under parts become jet-black. In the case of the immature birds, of A. gambeli especially, advancing towards maturity, it is first a gradual extraction of the dark colouring matter from the feathers, eventually leaving the breast and under parts almost if not quite white; then the full drab colour of the adult bird gradually deepens, and with it the black colour begins to appear. As I have before said, these changes are accompanied by a moult, and probably by the time the breeding period comes round the whole body has been clothed in new feathers.
I have given these general facts here, as it will be necessary to keep them in view in connection with the following descriptions.
The general appearance of this bird's first plumage is a very dark blackish brown; but compare this first plumage with the black-breasted breeding stage, and it is easy to see that this young bird belongs to a parent who finds black under parts useful to it as a protective colouring during the breeding season. As the same conditions of environment prevail when the young bird has got his first feathers to those of the breeding period, it is equally necessary for the young to be darkly clad. We find plenty of instances of this in the cases of the various kinds of Ducks, Guillemots, Razorbills, Dunlins, and other shore birds, where the first plumage after the downy stage closely resembles that of the adult breeding-dress.
The whole of the under parts, then, in this young bird, from the breast to the abdomen, are a deep blackish umber, fringed with pale drab. The flanks not quite so dark in colour, but fringed with a darker drab. The mantle is dark umber, with pale, faded brown margins; rump very dark umber; upper tail-coverts—central ones dark umber, fringed with dirty white; outer ones dark umber on one side of the rib, dirty white the other. Tail blackish umber, margined with dirty white. The forehead extending to the eyes; loral region and front cheeks a dull black, with a few indistinct white feathers scattered around base of bill and forehead; the rest of the head and neck a dark drabish umber, darkest on top and back of neck; the front lower neck a lighter drab. The wing-coverts graduate from the slaty drab of the extreme outer ones to the blackish umber of the medians, faintly fringed with paler; the primary coverts are a slaty umber, broadly margined with white. Primaries blackish umber, with white shafts; secondaries almost black with a very delicate hairline margin of drab. The alula and base of primaries slaty drab. Abdomen and under tail-coverts dull white. The legs, toes, and webs a pale chrome-yellow, with a tinge of umber. Bill a dirty whitish yellow with a few streaks of blackish on ridge and side. Nail whitish at base, blackish at end streaking into the white. Iride dark hazel; eyelid brownish yellow.
Length 29½ in.; weight 5 lb.; bill 1·98 in.; tarsus 2·75 in.; wing 15¾ in.
It is a pity I have not got the absolutely first plumage of this bird; however, the only traces shown of the second stage are a few large feathers on the flanks, and a larger sprinkling of white on the forehead; it may practically be taken as a first-plumaged bird, and it at once gives us a totally distinct-looking appearance to the first specimen or any other immature stage of A. gambeli. Here we have a bird whose parents do not require entirely black under parts for the breeding period! The whole of the under parts, from the breast to the abdomen, are a pale stone drab fringed with lighter, and becoming almost white towards the abdomen. None of these feathers shows the slightest traces of having had the dark colouring matter in them which is to be found up to the fourth stage in A. gambeli. The flanks are a darker drab with pale margins. The mantle is pale umber margined with drab. Rump blackish umber; upper tail-coverts much paler than in gambeli, being a washy brown and dirty white. The tail is very like that of gambeli, but a paler tint of dark umber. Round the base of the bill and under the throat a fair space of dirty white feathers interspersed with blackish ones; forehead and front cheeks blackish, but in no way as dark as the other bird; head and neck a dark rusty drab, darkest on crown and back of neck. Outer wing-coverts slaty drab, gradually darkening into deep umber margined with paler of the medians, and slaty drab broadly margined with dirty white of the first coverts. Primaries dark umber but with a light hoary shading, secondaries nearly black. Alula and base of primaries a hoary slate. Abdomen and under tail-coverts dirty white. There was not sufficient difference in the colours of soft parts in these two birds to induce me to make special notes, and I find that in my manuscript book which I keep for recording colours of soft parts the one description answers for both birds; but the legs and bill look much paler now than those of the first specimen. The ridge of the bill shows traces of dark markings, and the nail is partly brown and dirty white. I did not take length and weight of this bird before skinning. Wing 15 in.; bill 1·85 in.; tarsus 2·45 in.
I can now take these three stages more briefly. In the second stage—male—one can unmistakably see the commencement of the fading away of the dark colouring matter which characterises the first plumage. In this bird the under parts have become a dirty-looking umber; on the upper part of the breast there are a few feathers left marbled with blackish umber, these alone showing clearly enough that it is a case of the extraction of the dark colouring matter. The upper breast is drab, with the edges of the feathers worn and abraded-looking. The flanks have a few of the dark large new feathers coming, bordered with dull white. The general appearance of the upper parts is paler than in first plumage, the bill is clearer, and the nail nearly all white. Bill 2·13 in.; tarsus 2·65 in.; wing 15½ in.
In the third stage the under parts have now assumed that appearance which the Americans call "speckle belly," the dark markings having so far faded away that the centres only of the feathers remain dark, making the under parts look as though speckled all over with dark umber. It is not necessary to describe any other portions of this bird's plumage, excepting that there is scarcely a trace of white at the base of the bill, and the blackish has a rusty look.
Male.—Length 28¾ in.; wing 16 in.; weight 5½ lb.; bill 2·13 in.; tarsus 2·93 in. The nail on bill is entirely dark.
The fourth stage is very interesting; it is still a "speckle-belly," but the clean-looking new greyish drab feathers are appearing on the upper breast and amongst the under parts, which are becoming almost white, while some of the old feathers have almost entirely lost the dark centres, giving a much whiter appearance to the under parts, which makes the speckles show up more distinctly. The flank feathers are well grown, and have broad white outer margins. The upper tail-coverts have become almost entirely white. There is a good space of white at the base of the bill, which is clearer yellow with the nail partly white. In the wing this bird shows the paler slaty drab outer wing-coverts, which runs through the rest of the series, becoming palest in the black-breasted adults, and in this differing distinctly from the adults of A. albifrons.
Male.—Length 28½ in.; wing 16½ in.; weight 5¼ lb.; bill 2·1 in.; tarsus 2·95 in.; neck 8¾ in.
It will be observed that I lack stages two and three in this bird. But my first specimen gives me first and some of the second characters, while the present, which is a very interesting bird, gives me the fourth and some of the fifth. Compare this bird with the fourth stage of A. gambeli, and the general tone of colouring will be found to be quite distinct. Instead of the under parts becoming almost white, as they do eventually in the larger bird, in this they are a stone drab down to the abdomen, which is certainly a very important distinction. On the under parts there is a moulted black feather here and there, drab ones with the black colouring being thrown into them, and a few with the darker drab of the first plumage not all extracted. There is no trace of this bird ever having been a "speckle-belly." On the head and neck there is more of a slaty tinge. The mantle and outer wing-coverts are much darker. There is a broad space of white at the base of the bill, which also extends low down under the throat; but there may be a tendency to albinism in this bird, as there are a few white feathers scattered on the neck; nevertheless, it is as well to point out that the white extends under the throat in the first plumaged bird, but is not traceable in any of the immature specimens of A. gambeli.
Female.—Length 26 in.; weight 4½ lb.; wing 15 in.; bill 1·80 in.; tarsus 2·52 in.; neck 7½ in.
In the fifth stage of this bird, which I miss in my series, but am well acquainted with, the whole of the under parts have become a dull white, with a black feather showing here and there.
In the sixth stage the drab colouring matter—now pale—has been thrown into the previously white feathers of the under parts; large patches and broken bands of black are appearing as the result of moult combined with the deposition of the black pigment. It appears to me that up to this sixth stage the bird has got new feathers on all parts of its body, so that all the important subsequent changes are a result of the continued deposition of the colouring matter into the feathers. In this specimen there is an extraordinary amount of white on the front of the head extending beyond the commencement of the eyes. Dissection proved it to be an immature male.
Length 28 in.; wing 16½ in.; weight 5 lb. 2 oz.; bill 2·17 in.; tarsus 2·91 in.; neck 9 in.
Seventh stage. The drab of the under parts has become more pronounced, while the black has greatly increased, and now forms almost unbroken bands across the lower parts; great numbers of the drab feathers have the black pigment being thrown into them.
Adult male.—Length 29 in.; wing 18 in.; weight 5 lb.; bill 2·24 in.; tarsus 3·0 in.
In all these four stages the colour of the soft parts is much deeper than in corresponding stages of A. albifrons, being of a distinct deep reddish orange. In some the entire bill is a bright orange scarlet, the nail also being suffused with red while the bird is quite fresh. The brilliancy of colour in the legs and bill appears to increase as the bird nears the breeding stage. Tongue and inside mouth white. Eyelid yellowish umber.
Eighth stage. All that need be said here in connection with this bird is to note the largely increased amount of black on the under parts, which extends almost to the vent, and has ceased to form bars; they are great patches with drab feathers interspersed.
Female.—Length 27½ in.; weight (a thin bird) 4¼ lb.; bill 2·1 in.; tarsus 2·75 in.; wing 16½ in.; neck 9 in.
Ninth stage shows a still further increase of black on the under parts, and leads up directly to the final two breeding birds.
Female.—Length and weight not taken; wing 17½ in.; bill 2·1 in.; tarsus 2·85 in.
In the sixth and seventh stages of this bird it is very evident that the under parts had become much paler than in the fourth stage before the black colouring matter began to appear; but in no case anything near as white as in gambeli. In the seventh stage the drab is appearing, in the eighth it has increased in intensity, as have also the black markings. In all these three the black markings are much less than in the gambeli series, and in all cases completely broken by the drab feathers. In this it will be seen that my observations agree perfectly with those of other writers. In all these birds the outer wing-coverts are much darker than in the series of gambeli.
The legs and toes are a bright orange yellow. Bill pale livid yellow. Nail shining white with a tinge of slate. Iride dark hazel, and eyelid dark drab. The measurements and weights of these I give in order:—Length 27½ in.; wing 16¼ in.; weight 5¼ lb.; bill 1·85 in.; tarsus 2·60 in.; neck 7½ in.Length 27½ in.; wing 16 in.; weight 5¼ lb.; bill 1·80 in.; tarsus 2·60 in.Adult female: Length 27 in.; wing 16½ in.; weight 5½ lb.; bill 1·80 in.; tarsus 2·65 in.
It remains now to describe the two last and most important stages in this bird. The breeding bird with entirely black under parts is exceedingly rare in collections, and I think has never been fully described, even by American writers! Audubon ('Birds of America,' vol. vii. p. 209) had evidently heard of such a plumage but not seen it, as he says: "Feeling pretty confident that in summer the lower part of the body becomes pure black." Dr. Elliot Coues ('Key to North American Birds,' p. 684) says, "in high plumage perhaps mostly black," so that he had never seen the bird, and probably only copied Audubon's indecisive remarks. The only references I can find amongst British writers are in Ussher's 'Birds of Ireland,' p. 170, and the late John Cordeaux in 'British Birds, their Nests and Eggs,' vol. iv. p. 591, who refers to a specimen in the collection of Mr. Gr. H. Caton Haigh; but both writers regarded these birds—which were obtained from Ireland—as being A. albifrons. If Mr. Ussher and Mr. Haigh will kindly examine their specimens, they will probably find that they are of the large-billed race.
In treating of the ninth stage I said that the black had increased so much that it led directly up to this tenth stage. In this the black covers the whole of the under parts and flanks from the lower neck to the abdomen, being interspersed here and there only by a single drab feather; the flanks show most drab, but it can easily be seen that the black colouring matter is being passed into these feathers. The other portions of the bird, from the head to the mantle, have also become much darker, but the outer and greater wing-coverts have become of a paler slate, while the median coverts are darker than in preceding specimens. Length 26½ in.; wing 15½ in.; weight 5 lb. 2 oz.; bill 1·95 in.; tarsus 2·62 in. In the eleventh stage it need only be said that the black has still further intensified, become more glossy, extends entirely over the flanks, the outer feathers of which have broad white margins, and that there is only just a trace of drab left. It is quite certain that if the bird had lived a few weeks longer there would not have been a solitary trace of drab left.
It is quite clear to me that these birds select for their breeding site a spot where there is black sand and scattered lumps of black lava with portions of the surface weathered drab! just such spots as I found in Iceland (ante, 1901, p. 409), and which are also to be found in any volcanic area in the far north. Here, by throwing themselves into that upright attitude which I saw the Greylags (Anser cinereus) do, they would make themselves look, even from a short distance, exactly like weather-beaten lumps of black lava. The white front to the head is of the highest value to the bird for protective purposes, as it shines conspicuously, but is comparatively such a small speck, and terminates so abruptly by reason of its black border, and then is so softened down by the red bill that you cannot associate it at first sight with a living creature; and so it completely distracts attention from the sombrely clad body of the bird! Thus we see that what appears to us—if we examine a cabinet specimen or an illustration—to be a glaringly conspicuous mark for betraying the bird, is utilised by nature as a potent factor for the bird's protection at the most important period of its life!
Adult female.—Length and weight not kept; wing 15¾ in.; bill 2·12 in.; tarsus 2·65 in.
I have given the descriptions of the two species alternately, so that the various plumages may be more readily compared.
Any ornithologist looking at the series of A. gambeli when they are placed side by side in a row, with their breasts all forward, could never doubt that they all belonged to one and the same species, judging by plumage alone. Upon scrutinising the series of A. albifrons under similar conditions, it is also equally clear that they belong to one and the same species, and that those species are distinct and easily separable. Turn all the birds round and examine the outlines of the bills, and the difference will be seen to be very striking. When one's eyes become thoroughly accustomed to these outlines, it is perfectly easy to separate the species by bills alone.
I now come to a very important point. I have said that I have discovered a further valuable osteological distinction: it is that the neck in A. gambeli is about 1½ in. longer than in A. albifrons.
Up to January last I had secured all my specimens singly, and had not noticed the difference in the length of neck; but in that month I was fortunate enough to get two specimens at one time—an immature gambeli and adult albifrons, and when the two birds were lying before me I was instantly struck by the extraordinary difference in the lengths of their necks. After skinning the birds and dislocating the necks at the base of the skull, the measurements were:—Adult albifrons 7½ in., and immature gambeli 9 in. I should not have attached too much importance to this single instance, but I was enabled during February to abundantly corroborate this evidence by getting two adult gambeli which gave me necks of 8¾ in.[2] and 9 in.; also another adult albifrons with a neck 7½ in.
I think, in the foregoing remarks, I have given abundance of proof in differences of plumage and osteological characters already well known to fully establish the distinctions between the two birds; but the final discovery ought surely to be all that is required to prove the specific validity of Anser gambeli.
It will perhaps be useful to give here, in tabular form for easy comparison, the measurements and weights of the various specimens:—
| A. gambeli. | A. albifrons. | ||||||||||||
| Stages. | Length. | Weight. | Wing. | Bill. | Tarsus. | Neck. | Length. | Weight. | Wing. | Bill. | Tarsus. | Neck. | |
| IN. | IN. | IN. | IN. | IN. | IN. | IN. | IN. | IN. | IN. | ||||
| 1 | 29½ | 5 lb. | 15¾ | 1·98 | 2·75 | — | — | — | 15 | 1·85 | 2·45 | — | |
| 2 | — | — | 15½ | 2·13 | 2·65 | — | — | — | — | — | — | — | |
| 3 | 28¾ | 5½ lb. | 16 | 2·13 | 2·93 | — | — | — | — | — | — | — | |
| 4 | 28½ | 5¼ lb. | 16½ | 2·1 | 2·95 | 8¾ | 26 | 4½ lb. | 15 | 1·80 | 2·52 | 7½ | |
| 5 | — | — | — | — | — | — | — | — | — | — | — | — | |
| 6 | 28 | 5 lb. 2 oz. | 16½ | 2·17 | 2·91 | 9 | 27½ | 5¼ lb. | 16¼ | 1·85 | 2·60 | 7½ | |
| 7 | 29 | 5 lb. | 18 | 2·24 | 3·0 | — | 27½ | 5¼ lb. | 16 | 1·80 | 2·60 | — | |
| 8 | 27½ | 4¼ lb. (thin) | 16½ | 2·1 | 2·75 | 9 | 27 | 5½ lb. | 16½ | 1·80 | 2·65 | — | |
| 9 | — | — | 17½ | 2·1 | 2·85 | — | — | — | — | — | — | — | |
| 10 | 26 | 5 lb. 2 oz. | 15½ | 1·95 | 2·62 | — | — | — | — | — | — | — | |
| 11 | — | — | 15¾ | 2·12 | 2·65 | — | — | — | — | — | — | — | |
It will be seen from this that A. gambeli, taken all round, is a larger bird, with a proportionately much longer neck, than A. albifrons. Add to this a yellowish umber eyelid against dark drab, and reddish orange legs and bill against orange yellow legs and pale livid yellow bill.
I will here again refer to Mr. J.H. Gurney's paper above cited, and say how thoroughly I agree with him in his contention that all three White-fronted Geese should be treated as distinct species. I have already said sufficient with regard to the two larger ones; but now place my A. erythropus amongst the whole of the specimens, and it stands out instantly and conspicuously as distinct from all.
Mr. Gurney refers to A. erythropus having been described as being no larger than an Eider Duck, or even a Mallard. This is quite right so far as length and weight goes, for I have had Eider Ducks 5¾ lb. weight and length 28 in., measured to the toes, and Mallards 4 lb. with length exceeding 22 in., but the comparison goes no farther than this. This Eider of 5¾ lb. and 28 in. long exceeds the length and weight of the largest specimen of A. gambeli, but it does not look as large as A. erythropus of 4½ lb. The fact appears to be overlooked that the feathers clothing the body of an adult Wild Goose are very much larger than those on the body of an Eider Duck, which makes the former look conspicuously larger than the latter. Those writers who describe the lesser White-fronted Goose as being about the size of a Brent Goose make a far more commonsense comparison. My specimen of A. erythropus, which weighed 4½ lb., was a very plump, indeed quite fat, bird; in the normal condition of flesh in the breeding season I can quite understand that it would weigh 4 lb., or even under, which was the weight of Mr. Popham's bird shot on the Yenesei. Mr. Chapman's bird at 2½ lb. was obviously in very poor condition.
Finally, it only remains now to discuss the probability of Anser gambeli crossing the Atlantic to the west coast of Ireland, or coming by some other route. I will at once and most emphatically express my opinion that there is nothing in the faintest degree unreasonable in suggesting that they can and do accomplish this journey easily and regularly. But we all know that these birds breed in the high north, and my own investigations in Iceland proved to me that White-fronted Geese only rest regularly there during the migratory period; which species I cannot say, but as likely to be gambeli as albifrons. Instead of the across Atlantic journey, it is more reasonable to assume that these birds come across Greenland—even if they do not breed there—to Iceland, and could then easily continue their journey downward, fringing the narrowest part of the Atlantic to Ireland. If Greenland and Iceland Falcons and so many other northern birds do it regularly, why not the powerful flying Wild Geese? If the Snow Goose (Chen hyperboreus) comes, why not A. gambeli? For my own part I should not doubt that they could easily cross even the broad part of the Atlantic.
The scepticism which has for so many years been indulged in with regard to American migrants visiting Great Britain must surely be utterly swept away now by the fact of so many American birds visiting our islands. The fanciful assisted passage theory is utterly inadequate to explain it, although it is perfectly certain that some birds do rest on vessels at sea, and travel with those vessels for a time, as instances have come under my own notice. But these occurrences are in no way sufficiently frequent to account for the great and increasing numbers of American birds which are coming to us—especially amongst the Waders. Even Yellow-billed Cuckoos and Carolina Crakes are just as genuine migrants as Snipe-billed Sandpipers, American Bitterns, Spotted Sandpipers, or American White-fronted Wild Geese.
There is one fact which all must admit, which is that of late years some birds are changing their lines of migration; further, that, in many instances, those birds breeding in the far north do not all take one line of migration for their winter quarters, but some go east, others come west. Take for instance the case of the Snow and Lapland Buntings; great flocks of both these species make for the American Continent, whilst other flocks come to us. What one species of bird will do, others will also; and is there anything unreasonable in suggesting that some flocks of A. gambeli make for the American Continent, while others come to our shores? It will, I think, be but reasonable to look for more American bird visitors in the future.
When we can obtain the services of some competent field naturalist who thoroughly understands the differences in the notes of birds, and who will have an opportunity of studying both A. albifrons and A. gambeli at their breeding haunts, we shall probably find that the habits and the notes of the two species are distinct. I quite understand the difficulties of studying the breeding habits of these birds, in consequence of the high northern districts selected by them for nidification being almost inaccessible to most naturalists, but I will urge that anyone whose good fortune it may be to pass a season in these regions can render a great service to ornithology by paying particular attention to this subject.
Before concluding this paper, I ought perhaps to say a few words of explanation upon two subjects I have touched upon during the progress of my arguments, viz. the power possessed by birds of extracting from and transmitting to their feathers colouring matter. The latter—colour change independent of a moult—has been dealt with by several writers latterly, but, in my judgment, not thoroughly. It will be seen that my views are very strong on the point—they have been so for a good many years past—and I have accumulated a mass of evidence which appears to me to place the matter beyond doubt; nevertheless, an intelligent study of the case of the White-fronted Geese alone ought to be sufficient to satisfy even our American friends. The former case—extracting the colouring matter from the feathers—is, I think, new. This point also I have not broached without due consideration, and during many years' study have amassed evidence of a most conclusive character. I formulated my views in a paper as far back as 1896, but for certain reasons did not allow it to be published at the time, and have since been too much occupied with other matters to revert to it.
- ↑ See online copy in BHL; with drawing (Wikisource-Ed.)
- ↑ Injured by shot.
This work was published before January 1, 1929, and is in the public domain worldwide because the author died at least 100 years ago.
Public domainPublic domainfalsefalse