214 THE ZOOLOGIST. 



Wales and the facing part of Ireland (£. e. where the Tuskar 

 Kock and adjacent coast of Co. Wexford are situated), it is quite 

 likely that these Swallows when making out to sea in the initial 

 phase of emigration, en route for the main track leading to their 

 southern destination, overshot the mark, as it were, i. e. drifted 

 westward out of their course, and then, owing to their powerful 

 speed of flight and great keenness of eyesight, only very few 

 minutes elapsed before they espied the outline of the Irish coast, 

 to which they steered. Not that they had any ultimate object 

 in immigrating to Ireland, but that they were attracted to 

 steer landwards simply to pick up a landmark en route as 

 they pursued their lengthened peregrinations. Practically all 

 the birds I observed passing the Tuskar Light- Station were 

 immature. Hence their passage across the comparatively narrow 

 part of St. George's Channel may simply represent a matter of 

 feeling their way. That immature birds are more prone than 

 adults to leave the track which takes them by the most direct 

 route to their ultimate destination is in part explained by the 

 greater number of the former appearing during migration at 

 unexpected sites. 



Owing to the remarkable degree of development of the sense 

 of vision in birds, especially their keen perception for form of 

 objects,* a sense developed altogether out of proportion to 

 all the others, it seems that one aid which birds receive in 

 seeking out their destination is the faculty they possess of 

 picking up, and recognizing the form of, certain landmarks, such 

 as mountain-ranges, great riversheds, coastlands, or portions of 

 coastlands with pronounced features, and, for aught we know, 

 great cities spread out beneath may serve as guides to the aerial 

 travellers. Young birds, unless they meet with adults, which no 

 doubt they do at all events for part of their journey, would, in 

 the initial phases of their migrations, have to find out their 

 landmarks, and no doubt several of these would be out of the 

 track and might afterwards be discarded. To say simply that 

 birds work out their migration-routes by instinct is in a large 

 measure merely begging the question, and certainly this concep- 



* Illustrative of this visual sense, I may poiut out that a tame Kestrel 

 which I had for eight years failed to recognize me, and seemed scared if I 

 wore a hat different to that which she was accustomed to see. 



