228 McAtee, Recognition Marks. LApril 



both when at rest and during flight. Such are, the white bands or 

 patches on the breast or belly of many birds, but more especially 

 the head and neck markings in the form of white or black caps, 

 collars, eye-marks or frontal patches 



" Recognition marks during flight are very important for all birds 

 which congregate in flocks or which migrate together; and it is 

 essential that, while being as conspicuous as possible, the marks 

 shall not interfere with the general protective tints of the species 

 when at rest. Hence they usually consist of well-contrasted 

 markings on the wings or tail, which are concealed during repose 

 but become fully visible when the bird takes flight 



" Most characteristic of all, however, are the varied markings of 

 the outer tail-feathers, whose purpose is so well shown by their 

 being almost always covered during repose by the two middle 

 feathers, which are themselves quite unmarked and protectively 

 tinted like the rest of the upper surface of the body." (p. 222.) 



Proceeding with the questions previously referred to : 



Why, if recognition marks are so important as a means of keeping 

 members of a flock together, do so many species of birds possessing 

 this type of coloration, migrate by night as well as by day, or even 

 migrate chiefly by night? 



Wallace, asserts that these marks "are very important for all 

 birds which congregate in flocks or which migrate together." 

 Yet practically all of the smaller migrants do most of their travel- 

 ling at night, when recognition marks can be of little or no service. 

 Even the bulk of the larger species, as Ducks, Geese and other 

 waterfowl, which do much traveling by day, have no difficulty in 

 making extensive migrations at night and in some localities they 

 habitually choose night-time for their lesser journeys. 



It is worthy of note that the principal exceptions to the rule of 

 night migration among the smaller birds, viz : Swifts, Nighthawks, 

 and Swallows, have one characteristic — the habit of feeding while 

 in full flight — in common. There is little doubt moreover that 

 this habit is the direct cause of their diurnal migration; that is to 

 say, recognition marks probably have nothing to do with it. 



If recognition marks are so valuable as a means of keeping 

 members of a species together, why is it that in the case of certain 

 species, every member of which has the same directive coloring, 

 the young birds and the adults migrate in separate flocks? 



