108 



BIRDS. 



in some measure blames the increase of Sparrows and the fact that 

 farmers now grudge to give the herd-lads a ten-shilling gun licence to 

 keep down the assertive hosts of these pests. This may well be in some 

 de{/ree, but I think it is quite as likely that there are other more powerful 

 causes at work. 



There seems to me to be very little doubt that Swallows feel a 

 change of temperature far in advance of the actual arrival of the change. 

 They usually migrate some time before any such change takes place, and 

 their well-known habit of gathering together in large companies, perching 

 on bare trees, or on the ledges of buildings, etc., is of course also a very 

 ordinary observation. This is previous to autumn migration. There 

 seems also to be no great doubt that birds are more sensitive to any 

 such changes than, say, we humans are I They have, most likely, if not 

 positively (to avoid theory), " nervous premonitions," which we can scarcely 

 perhaps realise. 



I think this can be easily shown from the collected accounts of 

 travellers and field naturalists, if desired. I will only refer to my own 

 experiences in one very typical instance, and that is the oft-repeated and 

 observed disappearance of clouds of mosquitoes in north-east Russia 

 long before the actual advent of the periodic north wind, i.e. at least 

 quite half an hour before we felt the slightest breath of the benefador. 

 So often did this occur, day after day, that at last the series of observa- 

 tions forced the conclusion that the mosquitoes had a long prior 

 admonition. 



Xow we have found that the Sand-Martin has the most northerly 

 dispersal of our three common species of Swallows — I mean generally 

 as regards its wider distribution in the world. Thus it appears that it 

 is the hardiest of our Swallows. And we find, I think, that in this country 

 at least it appears to be more constant in its numbers as a breeding species 

 than, for instance, the House-Martin. 



Nevertheless, and curiously, we find that the House-Martin appears 

 in by far the greater numbers in Scotland in our colder and u-etter surnnwrs ! 

 Whereas a superficial reasoner might say this disproves their being more 

 sensitive to climatic changes than its congener the Sand-Martin, I take 

 the opposite ^iew — whether I may be supported in it or not. I have 

 many times watched the swaying to and fro of spring migrants (I am 

 now dismissing autumn migrants) where the conditions of winter and 

 first spring seasons are under the influence of more potent and swift 

 degrees of change than in the comparatively moderate climate of our 

 isles, viz. in the Arctic, or at least in the sub-Ai'ctic regions. In the 

 north of Europe often have I witnessed flights of summer arrivals fly 



