SWALLOWS AND SWIFTS 153 



All these vicissitudes at nesting-time help to make the 

 numbers of the swallow tribe fluctuate from year to year, and 

 other accidents befall them on the two long migrations and 

 in their winter home. But if we look at the country as a 

 whole, it is very doubtful whether there is any such general 

 diminution of swallows and martins as is sometimes asserted. 

 The proved return of marked swallows to the same place in 

 successive years give a strong indication that this fidelity is 

 characteristic of their species, as it probably is of many of our 

 migrant birds. If the number of swallows and martins about 



HOUSE-MARTINS 



a certain group of buildings decreases in any year, it might 

 therefore be argued that many of them have perished. But 

 just as nightingales or chiffchaffs are not quite constant to the 

 same haunts, so it seems likely that many swallows are not 

 averse to shifting their quarters from year to year. If they 

 invariably revisited old haunts, it is clear that new outlying 

 buildings would never be populated by them. When it is 

 said that the number of swallows and martins in any spot 

 has declined, the comparison is often unconsciously made, 

 not with the general average of a series of years, but with 

 some year of unusual numbers in the past. And since a 

 considerable proportion of the birds are not wedded to one 

 spot, they may often increase in new haunts at the very 



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