146 STUDIES IN BIRD-MIGRATION 



the first to take leave of us. It is a single-brooded 

 bird, and does not linger anywhere in Europe, not 

 even in its nesting haunts in countries bordering the 

 Mediterranean, after its young are able to undertake 

 the long journey to the southern winter homes of the 

 species. On the 29th of July, 1887, hundreds of Swifts 

 were observed passing southwards at Yarmouth. 



Some of the birds enumerated, such as the Song- 

 Thrush, Pied Wagtail, Meadow- Pipit, Skylark, Starling, 

 Lapwing, and Curlew, belong to species which have 

 been defined as partial migrants — that is to say, a 

 proportion of the individuals composing them are migra- 

 tory and essentially summer visitors, whilst the rest are 

 sedentary, remaining in our islands all the year round. 



Passage Movements} — As the summer, more especi- 

 ally the northern summer, is yet young, it would scarcely 

 be expected that immigrants from the north or from 

 the Continent would arrive on our shores thus early 

 on their return to their winter quarters. Yet a number 

 do arrive, and the appearance of others may, perhaps, 

 be accounted for in the following ways : — They are 

 either (i) birds which have not proceeded so far on 

 their spring journeys as to reach the breeding grounds, 

 being either immature or barren birds ; or (2) if they 

 have done so, they have either failed to obtain mates, 

 or for some other reason have not reared families. Some 

 of them, indeed, may not have passed much beyond 

 British limits on their spring journeys north or east.^ 

 Most of the July immigrants occur late in the month, 



1 For particulars of the dates of Passage Movements, see p. 129. 



2 A number of Common and Velvet Scoters, Turnstones, Purple Sand- 

 pipers, Bar-tailed Godwits, and other northern breeding species, are known 

 to pass the summer with us as non-nesting birds. 



