92 BRITISH BIRDS. 



INCUBATION PERIOD OF THE 

 STONE-CURLEW. 



The exact period of incubation of many birds is often not 

 well recorded, and the following observations concerning- 

 the Stone-Curlew {G^dicnemus scolopax) may be worth 

 noting. May 23rcl — one egg laid early in the day. 

 May 25th — second egg laid late in the day, and incubation 

 commenced. June 20th — fii-st yomig one hatched in the 

 morning ; and the second egg with a large hole, and the 

 young one calling within the shell. June 21st— both 

 young had left the nest. The period of incubation was 

 thus in this instance from twenty-six to twenty-seven 



^^^^' E. G. B. Mbade-Waldo. 



THE "DRUMMING" OF THE SNIPE. 



An interesting paper on the " drumming " or " bleating " of the 

 Snipe was read by Mr. P. H. Bahr before the Zoological Society, 

 and is published in the " Proceedings " of that Society for 1907 

 (pp. 12-35). After discussing the various theories which have 

 been advanced to account for the sound, Mr. Bahr gives excellent 

 proof that in the Common Snipe (Gallinago ccelestis), at all 

 events, the " bleat " is produced by the two outer tail-feathers. 

 As the bird makes the downward swoop, the two outer tail- 

 feathers are held widely spread beyond the others — ^almost at 

 right angles to the body — as may easily be seen with a pair of 

 binoculars, but in addition to this Mr. Bahr states that he can 

 distinctly see these feathers vibrating during the performance 

 of the " bleat." By fixing these feathers to corks and whirling 

 them through the air, Mr. Bahr demonstrated that the sound 

 could be reproduced. There appear to be no special muscles to 

 control the outer tail-feathers, but the muscles at the base of the 

 feathers are suflficiently well developed to perform this function. 

 Ill structure these feathers differ fi'om the rest of the tail- 

 feathers. The shaft is firm, the outer web narrow with easily 

 separable rami, the inner web extremely broad with long stiff 

 rami firmly held together. It is this latter portion of the 

 feather which produces the sound — the radii, branching from 

 the rami, being firmly interlocked by means of the hamuli and 

 ciUa, which are exceptionally well developed. It is, indeed, the 

 great size of the hamuli which furnishes the "essential factor 

 in producing the ' bleat,' in that they hold the stiff rami together 

 like the strings of a harp." In the other tail-feathers the 

 hamuli are fewer and not so well curved, nor so thick. It 



