THE ORDER OF MIGRATION 201 



they principally consist of adult females ; in the third 

 week, follow the birds of the year ; whilst finally, during 

 the last week, arrive the cripples — birds which have lost 

 their toes, birds with half a tail, birds with one mandible 

 abnormally long, or birds with some other defect. In 

 autumn the order of migration is somewhat different. 

 For weeks before the regular period of migration is due 

 stragglers in various stages of plumage arrive, loaf about 

 in a desultory manner for a few days, and then disappear. 

 Some of these birds are in summer plumage, some of 

 them in their winter dress, whilst others are in a tran- 

 sition stage, moulting as they migrate. These avant- 

 coureurs are supposed to consist of barren birds, odd 

 birds who have been unable to find a mate, or birds 

 whose nests have been destroyed too late in the season 

 to allow of a second nest to be made. Having nothing 

 else to do, the hereditary instinct to migrate not being 

 checked by the parental instinct, they yield to its first 

 impulses, and drift southwards before the general body of 

 their species. When the period of migration sets in in 

 earnest, astounding as the fact is, it is nevertheless true 

 that the birds of the year are the first to migrate, birds 

 which of course have never migrated before. This 

 circumstance, which all the Heligolanders with whom I 

 conversed agreed in corroborating, may to a large extent 

 account for the fact that the rare stragglers recorded as 

 visiting Heligoland and other countries are for the most 

 part birds of the year on their first autumn migration. It 

 is not to be wondered at that on their first journey they 

 should frequently stray from the direct course. Probably 

 the mortality amongst birds of the year is very great, 

 especially amongst those who take the wrong road on 

 their first migration. The yellow-browed warbler {Phyllo- 

 scopus superciliosus, Gmel.) breeds in immense numbers 



