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ON A PLAN OF MAPPING MIGRATORY BIRDS 

 IN THEIR NESTING AREAS. 



BY 



C. J. AND H. G. ALEXANDER. 



After some years' observation of the birds in the 

 neighbourhood of Tunbridge Wells, we came to the 

 conclusion that in many species each pair inhabits a 

 definite area, into which other pairs do not intrude. In 

 the spring of 1907, therefore, we decided to mark in the 

 positions of these pairs on 6 in. Ordnance Survey Maps. 

 In that summer we mapped a considerable area round 

 Tunbridge Wells, while in the summer of 1908 we 

 increased this area, and also began mapping at Wye 

 (near Ashford). 



In placing a pair of birds on the map we generally relied 

 on the singing of the male, though in many cases we saw 

 the female as well, and occasionally found the nest. In 

 the migratory species of the Turdidce most individuals 

 sing persistently from their arrival (provided the weather 

 is suitable) to the time of pairing, less during the time 

 of nest-building, again more while the females are 

 sitting, and less after the young are hatched. A Chiff- 

 chaff at Wye apparently did not sing at all after it 

 began to build, and from this extreme all gradations 

 occur up to individuals which sing nearly as much all 

 through the rest of the song-period as just after their 

 arrival. 



When a bird of any migratory species appears at a 

 place on one day and is gone again on the next, it is 

 safe to assume that it is only on its way to its own 

 breeding-ground. Of such individuals we only see a 

 very few, both of species which breed in our districts, 

 and of species such as the Ring-Ouzel, Greenland Wheat- 

 ear, Redstart, and Common Sandpiper, which do not ; 

 the only occasion on which we have seen any number 



