OCR Text |
Show 22 DOMESTIC PIGEONS. CHAP. I. touch; the oil-gland is quite aborted .. Several other less distinct breeds might have been spemfied. In the skeletons of the several breeds, the develop-ment of the bones of the face in length and breadth and curvature differs enormously. The shape, as well as the breadth and length of the ramus of the lower jaw, varies in a highly remarkable manner. The number of the caudal and sacral vertebrre vary ; as does the number of the ribs, together with their relative breadth and the presence of processes. The size and shape of tho apertures in the sternum are highly variable; so is the degree of divergence and relative size of the two arms of the furcula. The proportional width of the gape of mouth, the proportional length of the eyelids, of the orifice of the nostrils, of the tongue (not always in strict correlation with the length of beak), the size of the crop and of the upper part of the cesophagus ; the development and abortion of the oil-gland; the number of the primary wing and caudal feathers ; the relative length of wing and tail to each other and to the body; the relative length of leg and of the feet ; the number of scutellre on the toes, the development of skin between the toes, are all points of structure which are variable. The period at which the perfect plumage is acquired varies, as does the state of the down with which the nestling birds are clothed when hatched. The shape and size of the eggs vary. The manner of flight differs remarkably ; as does in some breeds the voice and disposition. Lastly, in certain breeds, the males and females have come to differ to a slight degree from each other. Altogether at least a score of pigeons might be chosen, which if shown to an ornithologist, and he were told that they were wi~d birds, would certainly, I think, be ranked by him as well-defined species. Moreover, I do not believe that any ornithologist would place CHAP. I. DOMESTIC PIGEONS. 23 the English carrier, the short-faced tumbler, the runt, the barb, pouter, and fantail in the same genus ; more ~spec~ally as in each of these breeds several trulyInhented sub-breeds, or species as he might have called them, could be shown him. Great as the differences are between the breeds of pigeons, I am fully convinced that the common opinion of naturalists is correct, namely, that all have descended fr~m the rock-pigeon (Columba livia), including under t~Is term several geographical races or sub-species, which differ from each other in the most trifling respects. As several of the reasons which have led me to this belief are in some degree applicable in other cases I will here briefly give them. If the several breeds are ~ot varieties, and have not proceeded from the rock-pigeon, they must have descen~e~ ~rom a~ least seven or eight aboriginal stocks ; for It IS 1m possible to make the present domestic ?reeds by the crossing of any lesser number: how, for Instance, could a pouter be produced by crossing two breeds u~l~ss one of the parent-stocks possessed the charactenstic enormous crop ? The supposed aboriginal stock~ must a!l . have been rock-pigeons, that is, not bre~~ng ~r ~llmgly perching on trees. But besides C. hvia, With It.s geographical sub-species, only two or three other species of rock-pigeons are known ; and these have not any of the characters of the domestic breeds. H~nc? the supposed aboriginal stocks must either still e~Ist In the countries where they were originally domestiCat~ d, ~nd yet be unknown to ornithologists ; and this, cons1denng t~eir size, habits, and remarkable characters, see~s ~ery Improbable; or they must have become e~tinct In the wi~d state. But birds breeding on precipiCes, and good fliers, are unlikely to be exterminated. a~d the common rock-pigeon, which has the same habit~ With the domestic breeds, has not been exterminated |