196 Mr. H, Parker on Nidification and 



The special migrations above mentioned may perhaps assist 

 iu explaining this little-understood habit in the case of many 

 of the true migrants. In the first place, the Mannar district 

 has certainly not been the home of these special migrants 

 from prehistoric times. Previous to the construction of the 

 village tanks, all of which are artificial, there cannot have 

 been any seasonal movement of this kind. There are almost 

 no natural pools of fresh water ; and such as are found are 

 in the forest-tract surrounding the plain, and of small size 

 and not fi'equented by these birds. The streams are inter- 

 mittent and unsuitable. In the south-west monsoon they are 

 never the resort of more than an insignificant number of some 

 few of the larger Waders, and only a very few Cormorants 

 feed in them during the wet season. It is quite certain, 

 therefore, that the migration to Mannar (and, in fact, to a 

 considerable part of Ceylon, for the same reasons) has begun 

 since the formation of the tanks ; and the earliest date that 

 can be fixed for the construction of any of them is about 

 B.C. 450. There is every reason to believe that many in this 

 district were made between that date and B.C. 100. The 

 migration is therefore to Mannar, and not from Mannar ; 

 and hence it is also clear that the migrants formerly bred in 

 their original homes, and have since been induced to change 

 their habits in this respect. It seems to be proved, too, that 

 a period of about 2000 years is enough to establish a migra- 

 tion. For instance, the migration of the Moorhen is fully 

 established in this period ; and, strange as the fact may 

 appear, the annual visit takes place only to these tanks, the 

 bird, which is plentiful here, having hitherto been procured 

 but three times in other parts of Ceylon. 



The migration to Ceylon must have been due, in the 

 first instance, solely to the attraction of the food-supply. 

 Stragglers of some of the species which feed in both fresh 

 and salt water were no doubt accustomed to work down the 

 coast ; and when once the resources of the tanks were dis- 

 covered, few years would elapse before a regular stream 

 of migrants found its way to them annually. The flow 

 is certainly not from other parts of Ceylon, but much more 



