280 CONTRIBUTIONS TO THE ORNITHOLOGY OF INDIA. 



I saw a considerable number of these mounds, chiefly at 

 Galatea Bay, and there I examined some of them very 

 minutely. These were situated just inside the dense jungle 

 which commences at springtide high-watermark. It appeared 

 to me that the birds first collected a heap of leaves, cocoanuts, 

 and other vegetable matter, and then scraped together sand 

 which they threw over the heap, so as not only to fill up all 

 interstices, but to cover everything over with about a foot of 

 pure sand. I say sand but this term is calculated to mislead, 

 because it does not contain much silex, but consists mainly of 

 finely triturated coral and shells. After a certain period, 

 whether yearly or not, I cannot of course say, the birds scrape 

 away the covering sand-layer from about the upper three- 

 fourths of the mound, cover the whole of it over again with 

 vegetable matter, and then cover the whole in again with the 

 sand. In the large mound, an old one, into which I carefully 

 cut a narrow section from centre to margin, this arrangement 

 was very perceptible ; in it I thought I could trace, by the 

 more or less wedge-shaped portions of pure sand along the 

 base, the remnants of successive outer coverings of sand, the 

 basal portions of which have never been removed, ten or per- 

 haps eleven successive renovations of the mound; even the 

 central portion was perfectly cool. The vegetable matter had 

 in a great measure disappeared, leaving only the hard woody 

 portions behind, but showing where it had been by the dis- 

 coloration of the sand. The decay of the vegetable matter, 

 and the bird's habit (as I judge from appearances) of not re- 

 moving the basal portion of the sandy covering, at each reno- 

 vation, sufficiently explain why the mounds increase so much 

 more in radius than in height. 



A smaller mound, one as I take it still in use, though I could 

 find no eggs in it, contained a much greater amount of vege- 

 table matter, and was sensibly warm inside. I could make no 

 section of it, as it was too full of imperfectly decayed vege- 

 tation. I believe that the bird depends for the hatching of 

 its eggs, solely on the warmth generated by chemical action. 

 The succulent decaying vegetation, constant moisture, and 

 finely triturated lime, all combined in a huge heap, will 

 account for a considerable degree of artificial heat. 



I am by no means satisfied that only one pair of birds use 

 the same mound. On the coutrary the Nicobarese, I had 

 with me that day, explained as I understood that the one pair 

 begiu the mound, they and all their progeny keep on using and 

 adding to it for years, and as a discern/ 3 or whatever the wretches 



