MIGRATIONS OF BIRDS AT TUSKAR ROCK. 189 



themselves out by flying round and round the light for many 

 hours. At length, when day broke, they either settled down 

 on the balcony rails, or descended to the Eock, fatigued 

 to such a degree as to suffer one to capture them almost with 

 the hand.* 



The average height from the ground at which Swallows, on 

 diurnal migration, passed by was about forty feet ; but their 

 gyratory and undulatory movements through the air subjected 

 the altitude almost to an unlimited degree of variation. The 

 speed of flight was certainly up to one hundred miles an hour. 



Natural and Exceptional Fraternities. 

 I now pass on to consider two important features in connec- 

 tion with the above-mentioned diurnal migrants : one, the 

 extent to which the birds tend naturally to fraternize ; the 

 other, the factors which seem to be responsible for the formation 

 of larger communities than are usually seen. In regard to the 

 first feature, I may say that were one to make merely a few 

 casual observations on a small party of passing migrants, and 

 because these birds were not immediately followed by others, the 

 watch was discontinued, or, at all events, carried out in a dis- 

 connected way, then the fundamental feature of diurnal migra- 

 tion here would be lost sight of. That is to say, its more or less 

 continuous or chain-like character, which becomes evident only 

 when a lengthened watch was kept up, would not be observable. 

 For in this chain are links of various sizes and shapes, and here 

 and there gaps exist where the links are broken. Even when 

 an intermission of fifteen minutes or so takes place and no birds 

 are seen, and allowing that more than one link is severed, yet 

 the chain-like character, as the migrants stream past, singly or 

 in small parties, for perhaps six hours on end, is still quite 

 evident. Pipits formed a more continuous chain than did 

 Wagtails, but it is not my intention in this paper to enter into 

 details on the migrations of these or any other birds, which are 

 being dealt with respectively in separate articles. Suffice it to 

 say that, grouping Wagtails, Pipits, and Swallows together, 



* I did actually manage to capture a few Swallows in my hand, as the 

 birds were perched on the balcony railings at dawn. When liberated some 

 returned to alight almost in the same spot ; others descended to the Eock. 



