262 Among the Birds in Northern Shires. 



birds in the northern shires than in the southern 

 and south-western counties. The former area is 

 subject to much greater climatic vicissitudes, to 

 sudden falls of temperature, and heavy snowstorms, 

 disturbances that have a marked effect upon birds, 

 and cause them to wander to an extent seldom 

 remarked in the south-west, where conditions are 

 much more equable and the temperature uniformly 

 higher. For instance, we believe the isotherm of 

 January in Yorkshire and Lincolnshire is about 37, 

 whilst in the south-west of England it is as high 

 as 43. In one way the southern counties possess 

 perhaps an exceptional migrational interest, from 

 the fact that they are the first point of arrival as 

 they are the last of departure of birds moving north 

 or south into or from the British area. But many 

 of the northern shires are exceptionally fortunate, for 

 on their coast-line breaks that mighty tide of east- 

 to-west migration in autumn, as also that from the 

 north and north-east at that season, together with 

 the departures in the reverse direction in spring- 

 movements which are but faintly or never indicated 

 at all in the south-west of England. In that remote 

 district the tide of migration from the north and 

 north-east is comparatively weak and exhausted by 

 the time it is reached. 



In spring, migration in the northern shires is to 

 some extent, and in certain directions, perceptibly 



