EFFECT OF WINDS ON THE FLIGHT OF BIRDS. 23 



specially favourable for the passage of the North Sea " (Fifth 

 Report, p. 59), that is to say, for the passage of birds which 

 come from Norway, Denmark, and Holland. 



Although, when I lived at Cromer, my attention, like Mr. 

 Cordeaux's, used to be directed to all kinds of birds, I endea- 

 voured to exercise special supervision on Gulls, particularly 

 the Herring and Lesser Black-backed gulls (Lanes argentatus 

 and L. fuscus), the most plentiful and the easiest to watch. 

 I think it will be shown that these Laridae give a key to what 

 obtains in most other birds, for the wind which suits them — 

 and I shall show presently that in autumn it is always a 

 contrary wind — is most acceptable to nearly all species under 

 similar conditions. 



To what extent the Laridae are birds of passage on and over 

 the North Sea it would be hard to say, but it has been over 

 and over again remarked that as regularly as autumn comes 

 round, great numbers of them, chiefly of the two species just 

 named, are to be seen at Cromer passing along the shore and 

 always flying west, and more or less in the teeth of the wind, 

 which is very seldom absent at that gusty watering-place. 

 Many have been the surmises as to their destination and why 

 they should almost invariably adopt the same course and go 

 in the same direction, and several times I have corresponded 

 with Mr. Cordeaux about this subject. It is fortunate that 

 on the coast of Lincolnshire there should be a naturalist who 

 for a long period of years has made the migration of birds 

 a close study. In 1884 both Mr. Cordeaux and I, being on 

 the look-out, observed, though not simultaneously, a very 

 great migration of Gulls (albeit the word "migration" is 

 not altogether applicable) — he in Lincolnshire and I in Nor- 

 folk. Mr. Cordeaux had his attention drawn to the move- 

 ment, for that is a better expression, on September 25th, 

 and from that day to the 28th he and his friends were 

 absorbed spectators of very great numbers of Herring and 

 Lesser Black-backed Gulls flying in the teeth of a strong- 

 south-west wind. The passage lasted four days, ten hours 

 each day, and possibly during the night also (see the account 

 of it in the Sixth Beport on Migration, p. 65). 



A fortnight later, October 11th, very nearly the same thing 



