Page:The Migration of Birds - Thomas A Coward - 1912.pdf/41

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CAUSE AND ORIGIN OF MIGRATION
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Any observer may verify the assertion that birds regularly visit certain favourable food-bases by paying attention to the occurrences of birds of passage. The study of a county, for instance, shows that certain species show partiality for particular localities. Thus in Cheshire goldeneyes pass through every spring and autumn, and may be met with occasionally on any of the meres; but at Oakmere, in the Delamere district; one may he 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 sandpipcr 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