LmER5 



" ON INCUBATION." 



To the Editors of British Birds. 



Sirs, — Mr. Dunlop's interesting article on " Incubation" in your 

 last number (Vol. V., pp. 322-7) tends to throw a new light on an old 

 subject, but it seems to me that the writer does not distinguish suffi- 

 ciently between " standing over the eggs " and incubation proper. For 

 instance, it is the common and normal practice among domestic pigeons 

 for one parent or the other to be in constant attendance on the nest 

 after the laying of the first egg, but incubation does not begin until 

 the laying of the second egg forty-six hours later, and the young in- 

 variably hatch out practically simultaneously. Again, Moor-Hens- 

 (Gallinula chloropvs) always hatch the whole of their brood at the same 

 time, and until the whole clutch is laid the eggs are never warm. With, 

 regard to the Grebes, the writer seems rather confused. The covering 

 of the eggs by vegetation is surely a more effective mode of concealment 

 than the bird herself, and as the bird has no special means to drive off' 

 would-be enen\ies, her presence before incubation commences would 

 be a source of danger rather than of safety. The presence cf the parent 

 bird standing over the eggs and thereby concealing them is undoubtedly 

 true for some species, but the cases in which inciihation begins with the- 

 laying of the first egg are much scarcer and must not be confused with 

 th? former habit. J. Lewis Bonhote. 



Sirs, — ^In Mr. Eric B. Dunlop's article on "Incubation," in the- 

 May number of British Birds (Vol. V., p. 324), he refers to the Moor- 

 Hen {G. c. chloropus) as " ovitegous." 



This is entirely contrary to my experience. Of many nests examined, 

 mainly in the Epping Forest district of Essex, I have not come across 

 an instance of the bird commencing to sit before the completion of 

 the clutch. In the case of two nests which I had under close obser- 

 vation during 1911 and 1912 respectively, on a small pond at Woodford, 

 the bird was rarely to be seen in the vicinity of the nest before the- 

 full clutch was laid, but spent the day on a larger sheet of water some 

 300 or 400 yards distant 



Moreover, in the case of the 1911 nest, the eight young were all 

 hatched dxiring the course of one day, five during the morning and three- 

 during the afternoon, and not on successive days, as would have been> 

 the case had some eggs been incubated longer than others. 



