176 



DOMESTIC PIGEONS. 



Chap. V. 



of comparison the length from the base of the beak to the oil- 

 gland; and by this standard, out of twenty-six of the same 

 birds which had been thus measured, twenty-one had wines 

 too long, and only five had them too short. Tn the twenty-one 

 birds the wings exceeded in length those of the rock-pigeon, on 

 an average, by 1^ inch ; whilst in the five birds they were less 

 in length by only '8 of an inch. As I was much surprised that 

 the wings of closely confined birds should thus so frequently 

 have been increased in length, it occurred to me that it might 

 be solely due to the greater length of the wing-feathers ; for this 

 certainly is the case with the jacobin, which has wings of un- 

 usual length. As in almost every case I had measured the folded 

 wings, I subtracted the length of this terminal part from that of 

 the expanded wings, and thus I obtained, with a moderate degree 

 of accuracy, the length of the wings from the ends of the two 

 radii, answering from wrist to wrist in our arms. The wings, 

 thus measured in the same twenty -five birds, now gave a widely 

 different result ; for they were proportionally with those of the 

 rock-pigeon too short in seventeen birds, and in only eight too 

 long. Of these eight birds, five were long-beaked, 39 and this 

 fact perhaps indicates that there is some correlation between the 

 length of the beak and the length of the bones of the w T ings, in 

 the same manner as with the feet and tarsi. The shortening of 

 the humerus and radius in the seventeen birds may probably be 

 attributed to disuse, as in the case of the scapulae and furcula 

 to which the wing-bones are attached ; — the lengthening of the 

 wing-feathers, and consequently the expansion of the wings from 

 tip to tip, being, on the other hand, as completely independent 

 of use and disuse as is the growth of the hair or wool on our 

 long-haired dogs or long-woolled sheep. 



To sum up : we may confidently admit that the length of the 

 sternum, and frequently the prominence of its crest, the length 

 of the scapulae and furcula, have all been reduced in size in 

 comparison with the same parts in the rock-pigeon. And 1 



39 It perhaps deserves notice that be- 

 sides these five birds two of the eight 

 were barbs, which, as I have shown, 

 must be classed in the same group with 

 the long-beaked carriers and runts. 

 Barbs may properly be Called short- 



beaked carriers. It would, therefore, 

 appear as if, during the reduction of 

 their beaks, their wings had retained ft 

 little of that excess of length which is 

 characteristic of their nearest relations 

 and progenitors. 



