CAUSE AND ORIGIN OF MIGRATION 25 



Any observer may verify the assertion that birds 

 regularly visit certain favourable food-bases by pay- 

 ing attention to the occurrences of birds of passage. 

 The study of a county, for instance, shows that 

 certain species show partiality for particular locali- 

 ties. Thus in Cheshire goldeneyes pass through every 

 spring and autumn, and may be met with occasion- 

 ally on any of the meres ; but at Oakmere, in the 

 Delamere district, one may be almost certain of 

 seeing parties of this species any time during the 

 periods of passage. The curlew may be heard or 

 seen passing over any part of the county, but only 

 in the Delamere fields do we frequently meet with 

 flocks feeding in inland Cheshire. Before the winter 

 resident golden plovers have arrived in autumn and 

 after they have departed in spring, the favourite 

 fields are regularly visited by passing flocks, and 

 the lower reaches of the Mersey, where the common 

 sandpiper is rare as a summer resident, are visited 

 every autumn by parties of birds on passage. Chance 

 may lead a casual wanderer to a good food-supplying 

 spot, but the regularity of appearance suggests habit 

 and memory. 



A fact which supports the theory that birds 

 ramble far in search of food in their winter 

 quarters, is that in many species the winter range 

 is more extensive than the breeding area. Thus 

 Mr Cooke shows that the known breeding area of 



