XV 



travel at a great altitude, and migration takes place chiefly during the night. Mr. Seebohm 

 (op. cit. p. 255) says: — "The period of migration of each species lasts about a month. In 

 spring during the first week the flocks consist principally of adult males ; during the second 

 week they principally consist of adult females ; in the third week follow the birds of the year ; 

 whilst finally, during the last week, arrive the ci'ipples — 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 transition stage, moulting as they migrate. These 

 avant-couriers 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 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 line of migration is certainly not invariably from the south to the north in 

 the spring, and in the contrary direction in the autumn, as was supposed by some naturalists, 

 but the direction is frequently diagonal. Gatke informed Mr. Seebohm that in his opinion the 

 direction taken by some species is east and west, whereas Aeuckens, the birdstuffer on Heligoland, 

 maintained that birds migrate north-east in spring and south-west in autumn ; and this latter 

 hypothesis appears to me to be in many cases correct ; for when in Southern Spain in May I 

 observed large numbers of Grey Plovers, Little Stints, and Pygmy Curlews, birds which certainly 

 breed in the extreme north-east of Europe and in Northern Asia, passing in a north-easterly 

 direction, most of them being in almost full breeding-dress. That the line of migration taken 

 in the spring differs from that taken in the autumn reversed, seems certain, at least to a large 

 extent, to judge from the fact that many species which occur on the shores of Great Britain 

 in- the spring in considerable numbers, are seen, only in much smaller numbers, in the autumn, 

 and vice versa. 



A most interesting communication relative to the migration of birds has lately been pub- 

 lished by Mr. W. E. D. Scott (Bull. Nutt. Orn. Club, 1881, pp. 97-100), clearly showing that 

 birds not only migrate by night, but at a very great altitude, say of from one to four miles 



