176 COMMON BIRDS OF AN INDIAN GARDFA 1 



lead them to make use of it as a permanent place 

 for roosting and breeding. This, however, is hardly 

 an event to be desired, even by those who are most 

 interested in the study of their habits ; for they 

 are as gregarious as night-herons, and the establish- 

 ment of one nest is sure to be followed by that 

 of others in steadily increasing numbers, until the 

 place is disfigured and rendered intolerable by 

 accumulations of rubbish and an overpowering 

 stench of guano and decomposing fish. It is not 

 easy to make out what particular features in a 

 place serve to render it attractive as the site of 

 such a colony. The presence of well- wooded islets 

 is, doubtless, influential in determining the choice, 

 but it alone will not suffice. The great system of 

 ponds in the Botanic Garden contains many wooded 

 islets, but yet neither night-herons, cormorants, or 

 snake-birds ever showed any inclination to settle 

 there during all the years that I was in Calcutta ; 

 while an island in the Zoological Garden in 

 Alipur, which is 'much nearer to the town and 

 far more frequented by visitors, was some years 

 ago occupied by immense colonies of all three 

 birds. In this case the place was not invaded for 

 many years after it had been thickly wooded ; and 

 when the invasion began, it was not occupied by 

 all the three kinds of birds at once. For many 

 years the only species who nested in the island 

 were a certain number of paddy-birds, common 



