Migration in North-west Ceylon. 197 



probably from Northern or Central India. Some pecu- 

 liarities in the breeding-habits of Ploceus philippinus lead me 

 to suppose that it may come from Western Ceylon; but no 

 adequate diminution of the other species during the north- 

 east monsoon (but rather an increase) has been observed in 

 more southerly districts of the island. 



Partial migrations. — In the admirable introduction to his 

 ' History of the Bii'ds of Ceylon/ Major Legge has already 

 referred to a periodical absence of some species from the 

 coast. This is observable throughout the Mannar district ; 

 and in addition there is a departure^ perhaps not quite com- 

 plete, of Coccystes jacobinus, Merops viridis, and Terpsiplione 

 paradisi (in the red plumage), the latter removing only from 

 the immediate neighbourhood of the sea. The movement 

 appears to be due, as Major Legge states, to the agency of 

 the strong south-west winds, which blow with extreme violence 

 in Mannar. I surmise, however, that it is not caused by 

 their direct influence on the birds themselves, but by their 

 effect on the food of the birds, all of which, be it noted, are 

 insectivorous. It is certain that insects cannot fly during 

 strong winds without being carried away by them ; and the 

 result is that, in the littoral portion of the Mannar district, 

 few aerial insects are visible during the prevalence of the 

 south-west breezes. Flies (which abound in countless in- 

 satiable hordes before the break of the monsoon), mosquitoes, 

 and most beetles, moths, and butterflies alike disappear. In 

 fact, in that tract the south-west monsoon is characterized by 

 a general scarcity of winged insect life. Naturally, then, the 

 first south-west winds are the signal for the inland movement 

 of certain species of birds also. That the rains do not aii'ect 

 this partial migration is shown by its occurrence here, where 

 often no rain, and never very much, falls at the heat of this 

 monsoon or during its continuance. 



The conclusions that would seem to follow from the facts 

 thus observed are, therefore, as follows : — 



1 . That the time and place of nidification are determined by 

 the food -supply and the feeling of security, and not by weather 

 or climate. 



SER. V. VOL. I. • p 



