The Variation of Animals and Plants under Domestication Volume I Part 14

Bussorah Carrier. 2.17 ..

0.09

Number of specimens. 28 22 5

I measured most of the birds which came into my possession, from the feathered BASE of the beak (the length of beak itself being so variable) to the end of the tail, and to the oil-gland, but unfortunately (except in a few cases) not to the root of the tail; I measured each bird from the extreme tip to tip of wing; and the length of the terminal folded part of the wing, from the extremity of the primaries to the joint of the radius. I measured the feet without the claws, from the end of the middle toe to the end of the hind toe; and the tarsus and middle toe together. I have taken in every case the mean measurement of two wild rock-pigeons from the Shetland Islands, as the standard of comparison. The following table shows the actual length of the feet in each bird; and the difference between the length which the feet ought to have had according to the size of body of each, in comparison with the size of body and length of feet of the rock- pigeon, calculated (with a few specified exceptions) by the standard of the length of the body from the base of the beak to the oil-gland. I have preferred this standard, owing to the variability of the length of tail.

But I have made similar calculations, taking as the standard the length from tip to tip of wing, and likewise in most cases from the base of the beak to the end of the tail; and the result has always been closely similar. To give an example: the first bird in the table, being a Short- faced Tumbler, is much smaller than the rock-pigeon, and would naturally have shorter feet; but it is found on calculation to have feet too short by .11 of an inch, in comparison with the feet of the rock-pigeon, relatively to the size of the body in these two birds, as measured from the base of beak to the oil-gland. So again, when this same Tumbler and the rock-pigeon were compared by the length of their wings, or by the extreme length of their bodies, the feet of the Tumbler were likewise found to be too short in very nearly the same proportion. I am well aware that the measurements pretend to greater accuracy than is possible, but it was less trouble to write down the actual measurements given by the compa.s.ses in each case than an approximation.

TABLE 5.II.

PIGEONS WITH THEIR BEAKS LONGER THAN THAT OF THE ROCK-PIGEON, PROPORTIONALLY TO THE SIZE OF THEIR BODIES.

Column 1. Name of Breed.

Column 2. Actual length of Feet (inches).

Column 3. Difference between actual and calculated length of feet, in proportion to length of feet and size of body in the Rock-pigeon.

Column 3a. Too short by (inches).

Column 3b. Too long by (inches).

1. 2. 3a. 3b.

Wild rock-pigeon (mean measurement). 2.02

Carrier. 2.60 ..

0.31

Carrier. 2.60 ..

0.25

Carrier. 2.40 ..

0.21

Carrier, Dragon. 2.25 ..

0.06

Bagadotten Carrier. 2.80 ..

0.56

Scanderoon, white. 2.80 ..

0.37

Scanderoon, Pigeon cygne. 2.85 ..

0.29

Runt. 2.75 ..

0.27

Number of specimens. 8 .. 8

In these two tables (Tables 5.I.and 5.II.) we see in the first column the actual length of the feet in thirty-six birds belonging to various breeds, and in the two other columns we see by how much the feet are too short or too long, according to the size of bird, in comparison with the rock- pigeon. In the first table twenty-two specimens have their feet too short, on an average by a little above the tenth of an inch (viz. .107); and five specimens have their feet on an average a very little too long, namely, by .07 of an inch. But some of these latter cases can be explained; for instance, with Pouters the legs and feet are selected for length, and thus any natural tendency to a diminution in the length of the feet will have been counteracted. In the Swallow and Barb, when the calculation was made on any standard of comparison besides the one used (viz. length of body from base of beak to oil-gland), the feet were found to be too small.

In the second table we have eight birds, with their beaks much longer than in the rock-pigeon, both actually and proportionally with the size of body, and their feet are in an equally marked manner longer, namely, in proportion, on an average by .29 of an inch. I should here state that in Table 5.I. there are a few partial exceptions to the beak being proportionally shorter than in the rock-pigeon: thus the beak of the English Frill-back is just perceptibly longer, and that of the Bussorah Carrier of the same length or slightly longer, than in the rock-pigeon. The beaks of Spots, Swallows, and Laughers are only a very little shorter, or of the same proportional length, but slenderer. Nevertheless, these two tables, taken conjointly, indicate pretty plainly some kind of correlation between the length of the beak and the size of the feet. Breeders of cattle and horses believe that there is an a.n.a.logous connection between the length of the limbs and head; they a.s.sert that a race-horse with the head of a dray-horse, or a grey-hound with the head of a bulldog, would be a monstrous production. As fancy pigeons are generally kept in small aviaries, and are abundantly supplied with food, they must walk about much less than the wild rock-pigeon; and it may be admitted as highly probable that the reduction in the size of the feet in the twenty-two birds in the first table has been caused by disuse (5/38. In an a.n.a.logous, but converse, manner, certain natural groups of the Columbidae, from being more terrestrial in their habits than other allied groups, have larger feet. See Prince Bonaparte 'Coup d'oeil sur l'Ordre des Pigeons.'), and that this reduction has acted by correlation on the beaks of the great majority of the birds in Table 5.I. When, on the other hand, the beak has been much elongated by the continued selection of successive slight increments of length, the feet by correlation have likewise become much elongated in comparison with those of the wild rock-pigeon, notwithstanding their lessened use.

As I had taken measures from the end of the middle toe to the heel of the tarsus in the rock-pigeon and in the above thirty-six birds, I have made calculations a.n.a.logous with those above given, and the result is the same-- namely, that in the short-beaked breeds, with equally few exceptions as in the former case, the middle toe conjointly with the tarsus has decreased in length; whereas in the long-beaked breeds it has increased in length, though not quite so uniformly as in the former case, for the leg, in some varieties of the Runt varies much in length.

LENGTH OF STERNUM.

As fancy pigeons are generally confined in aviaries of moderate size, and as even when not confined they do not search for their own food, they must during many generations have used their wings incomparably less than the wild rock-pigeon. Hence it seemed to me probable that all the parts of the skeleton subservient to flight would be found to be reduced in size. With respect to the sternum, I have carefully measured its extreme length in twelve birds of different breeds, and in two wild rock-pigeons from the Shetland Islands. For the proportional comparison I have tried three standards of measurement, with all twelve birds namely, the length from the base of the beak to the oil-gland, to the end of the tail, and from the extreme tip to tip of wings. The result has been in each case nearly the same, the sternum being invariably found to be shorter than in the wild rock-pigeon. I will give only a single table, as calculated by the standard from the base of the beak to the oil-gland; for the result in this case is nearly the mean between the results obtained by the two other standards.

TABLE 5.III.

LENGTH OF STERNUM.

Column 1. Name of Breed.

Column 2. Actual Length in Inches.

Column 3. Too short by (inches).

1. 2. 3.

Wild Rock-pigeon. 2.55

Pied Scanderoon. 2.80 0.60

Bagadotten Carrier. 2.80 0.17

Dragon. 2.45 0.41

Carrier. 2.75 0.35

Short-faced Tumbler. 2.05 0.28

Barb. 2.35 0.34

Nun. 2.27 0.15

German Pouter. 2.36 0.54

Jacobin. 2.33 0.22

English Frill-back. 2.40 0.43

Swallow. 2.45 0.17