222 BRITISH BIRDS. 



noticeable when the bird is first driven from the ground 

 and during the earlier stages of the flight. This song is 

 evidently an expression of fear and is quite distinct from its 

 usual melody. Mr. Guy Blaine, who has successfully flown 

 Merlins for a number of years, writes to me as follows : — 

 " Late in September, when the Larks have completed their 

 moult and are confident of their powers of flight, I have 

 actually known them to rise up before a Merlin, singing all 

 the time and to continue their song into the sky." In this 

 case, of course, the song is normal and is perhaps " the 

 ebullition of superfluous energy" described by Mr. Stubbs. 



When fighting together many birds (Skylarks and Robins 

 are good examples) give vent to a series of angry twitterings : 

 these sounds very frequently develop into a defiant and well- 

 defined song. 



COLLINGWOOD INGRAM. 



NUMBER OF EGGS LAID BY TERNS, 



AND THE EFFECT OF FOOD-SUPPLY ON FECUNDITY. 



On July 2nd, 1904, I visited a large colony of Arctic Terns 

 (Sterna macrura) off the coast of co. Mayo, and here I found 

 that out of about 130 nests examined, only one had three eggs, 

 a few one egg only, and the rest two eggs. 



C. B. Ticehurst. 



I note with interest Mr. Bunyard's remarks in your last 

 issue, and appreciate what he says regarding the regulation of 

 the size of clutches by climatic conditions. I adhere absolutely 

 to my contention, however, that the food-supply is in most 

 cases responsible for the size of the clutch, and I should like 

 to point out that I support this by the fact that all my 

 observations are personal ones and taken on the spot. 



Ravens on the coast almost invariably lay more eggs than 

 inland birds ; where rabbits are abundant the Buzzard is more 

 prolific ; where the Sparrow-Hawk is allowed to have its own 

 way, clutches are larger; and to go back to Terns, the fry 

 which forms the large proportion of the food-supply is 

 certainly more abundant on the east and north coasts than on 

 west and south. The Wood-Lark in the sandy districts of 

 Norfolk very frequently lays five and, occasionally, six eggs, 

 whereas in Wales, where the favourite food is not so abundant, 

 the clutch, does not often exceed three. I know that in the 

 Orkney Islands the Skylark frequently lays five eggs, but 

 although such occurrences are much rarer in the south I 



