ON INCUBATION. 323 



Coming to the Turdidse, Mr. W. G. Sheldon, writing in 

 British Birds for November, 1911 — after stating that 

 the Fieldfare (T. j^ilaris) places its nest in a very con- 

 spicuous position — says that " the hen commences to sit 

 immediately the first egg is laid " (p. 153). 



The owls (Strigidse) are ovitegous in habit. In a clutch 

 of two eggs of the Tawny Owl (S. aluco) which I watched,, 

 one hatched on May 4th, the other two days later. This 

 species frequently lays in old Crows' nests, and even in 

 a Rook's nest in an inhabited rookery. The white and 

 conspicuous eggs would remain a ver}^ short time if left 

 exposed. The Eagle-Owl (B. ignavus) and Little Owl 

 [A. noctua) have both been recorded to sit from the first 

 egg. Similar cases have been noted of the Snowy Owl 

 {N. scandiaca) in the far north. It is worthy of remark 

 that in confinement the habit remains the same. In the 

 Zoologist for 1875, a pair is recorded to have bred in Mr. 

 Edward Fountaine's aviary : " The first egg was hatched 

 on the 1st of July, the second on the 3rd, the third on 

 the 6th, the fourth on the 8th, and the fifth on 

 the 9th."* 



The Columbidse also lay white eggs, and in many cases 

 in situations resembling those occupied by owls. The 

 analogy is particularly noticeable between the TaAvny 

 Owl and the Stock-Dove (C. oenas). I have frequently 

 known this pigeon to incubate from the deposition of the 

 first egg. The Ring-Dove (C. palumhus) often protects 

 its eggs in like manner, but this is not always the case. 

 Some domestic pigeons whose incubating habits I noted^ 

 also varied in this respect. Out of fifteen cases, eleven 

 sat as soon as the first egg had been laid, and four did not 

 incubate until the clutch was complete. The cock as 

 well as the hen sat before the second egg had been laid, 

 in several instances. 



* Although it is true that the Bam-Owl in many cases incubates 

 as soon as the first pair of eggs is laid, there are exceptional cases in 

 which the eggs are laid without the big pauses between the pairs, and 

 the difference of incubation is very slight. — F.C.R.J. 



