MIGRATORY RIRDS : SPRING 123 



species appear at stations where there is no mistaking 

 the nature of their visits. These are the remnants of 

 the rear-guard of the feathered army which has already 

 passed to its summer quarters, and in its ranks are to 

 be found Swallows, Martins, Red-backed Shrikes, Tree- 

 Pipits, Spotted Flycatchers, Willow-Warblers, Garden- 

 Warblers, Blackcaps, Common Whitethroats, Lesser 

 Whitethroats, Redstarts, Arctic Bluethroats, Swifts, 

 Nightjars, Cuckoos, Wrynecks, Corn-Crakes, and 

 Common Sandpipers. 



In connection with the arrival of the Summer Visitors, 

 an interesting fact remains to be related — one that was 

 first made known through the " Digest of Observations " 

 submitted to the British Association in 1896. When 

 studying the vast data amassed by the Migration 

 Committee, I found that the great majority of our 

 summer birds appeared on the west coast of England 

 some days in advance of their arrival in their eastern 

 haunts. More recent investigations have confirmed this, 

 and have made known to us that the same rule applies 

 to Scotland, where the Solway and Clyde areas receive 

 their first spring migrants some days earlier than the 

 areas of Tweed and Forth. Thus the Swallow arrives 

 on the south-west coast of Scotland several days 

 earlier than in the south-east. It is not unnatural that 

 the British summer birds should seek first those portions 

 of our islands which are the most genial at this early 

 period of the season. A reference to a map giving the 

 spring isotherms, shows us that in March the Solway 

 has an average temperature equal to that of the Thames, 

 the Clyde to that of the Tyne ; and that in April it is as 

 warm in Cantyre as it is about the Wash and H umber. 



