314 The Chiffchaff and Willow- Warbler. 



With regard to the Gibraltar-iree^m^ Chiffchaffs : — 



(fl) Are these non-migratory (i. e., resident) individuals, 

 or do they leave in winter to make room for winterers from 

 further north ? 



This is, of course, not so easy to find out^ since it is almost 

 certain that Gibraltar will receive its winter proportion of 

 Chiffchaffs from the north, irrespective o£ the movements 

 of the local breeders. 



Ringing and perhaps observations in March will perhaps 

 prove the most fruitful methods of attacking this little 

 problem. 



{b) Vvill examination of more specimens, particularly of 

 freshly moulted adults in autumn, show any peculiaiity 

 of form (including coloration) to distinguish these Gibraltar 

 birds from typical P. c. collybita ? 



(c) Does further experience show that the peculiarity of 

 the eggs is constant ? 



(d) When does the song commence in spring ? Is it 

 ever heard in winter ^ ? If a resident, and such were the 

 case, it would help towards the solution of {a). Is the song 

 always the same. Willow- Warbler-like? 



Dr. Hartert, who has very kindly interested himself in 

 the matter and to whom I have given the nest, eggs, and 

 specimens of the Gibraltar Chiffchaffs already alluded to, 

 permits me to say that he will be glad to compare them with 

 any otliers that may be sent to him in connection with this 

 particular question. 



With regard to the distribution question in general, I 

 think that the map itself, without further remark, shows 

 sufficiently the many gaps that can be filled in by the field- 

 ornithologist. 



* There are quite a few records of the Chiffchaff' s song being heard 

 in the Mediterranean basin in winter time. 



