292 BRITISH BIRDS. 



one \\"as addled, but the other contained a well-developed 

 chick, which, however, could not have hatched for several 

 hours, the yolk-sac not yet having been withdrawn into the 

 body. 



It seems, then — so far as this case is concerned — that the 

 egg of Cuculus canorus takes about two days less to incubate 

 than that of A. modular is, which require, according to Mr. 

 A. H. Evans {Ihis, 1891), tw^elve or thirteen days. That is 

 to say, the egg of the Cuckoo hatches after from ten to eleven 

 days' incubation — an abnormally short period. The ad- 

 vantage of this to a parasitic species is at once obvious, for 

 should hatching take place a day or two after the appearance 

 of the young of the host, it would be so seriously handicapped 

 as to have but a small chance of surviving. 



We may assume that other parasitic Cuckoos have developed 

 a similarly brief incubation period. Mr. W. H. Hudson 

 {Hampshire Days, p. 16) declares that this certainly is the 

 case with the parasitic genus Mololous of South America. 



As to the strange instinct that prompts the young Cuckoo 

 to eject the contents of the nest in which it finds itself, I maj^ 

 remark, that so far as my experience goes, this is developed 

 within fifty hours after birth, and ceases at about the sixth 



*^ ■^'" CoLLmowooD Ingram. 



[For some other observations on the incubation period in 

 the Cuckoo, see page 283, We take the opportunity of 

 throwing out the suggestion to egg-collectors that they 

 should make careful observations on incubation periods and 

 the development of the young rather than amassing series 

 of egg-shells. — Eds.] 



PINTAIL IN BERKSHIRE. 



A FEMALE Pintail (Dafila acuta) was shot at Hennerton. 

 Berkshire, on 23rd December, 1907, and sent to me in the 

 flesh. This is the first authentic record I have for the 

 county. Heatley Noble. 



WOOD-PIGEON SWIMMING. 



One morning last May I saw a Wood-Pigeon \\alk into the 

 Serpentine in Hyde Park and, after getting out of its depth, 

 paddle itself along, gently flapping its wings, for a distance 

 of about five yards. On my approach it rose from the surface 

 without difficulty and Hew to a tree on the island, which was 

 about fifteen yards further off. Instarices are on record of 

 various land-birds resting on water when tired. In Gatke's 



