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 perhaps 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 bad been by the discolouration of the sand.
The decay of the vegetable matter, and the bird's habit (as I
judge from appearances) of not removing the basal portion of
the sandy covering at each renovation, 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 vegetable
matter, and was sensibly warm inside. I could make no
section of it, as it was too full of imperfectly decayed vegetation.
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 contrary, the Nicobarese I had with
me that day explained, as I understood, that, though one pair
begin the mound, they and all their progeny keep on using
and adding to it for years; and they told us that they had,
during the previous month, taken at one time some twenty eggs
out of one and the same mound, which also they took us to see,
and which was perhaps five feet high and sixteen or eighteen
feet in diameter, and which was the freshest-looking I had
seen.
The eggs are excessively elongated ovals, enormously large
for the size of the bird. They vary a great deal in size, and a
good deal in shape ; all are much elongated, but some are more
like Turtles' eggs than those of a bird. When first laid, they
are of a uniform ruddy pink, as we know from having obtained
one before the bird had time even to bury it; after being buried,
so long as the egg remains quite fresh, it continues a pale pink,
but as the chicken develops within, the egg becomes a buffy
stone colour, and when near about hatching, it is a very pale
yellowish brown. The whole colouring matter is contained in
an excessively thin chalky flake, which is easily scraped off,
leaving a pure white chalky shell below. This outer coloured
coat seems to have a great tendency to flake off in spots, specks,
and even large blotches, as the chicken is developed within.
Quite fresh-laid eggs rarely exhibit any white marks of any
kind, while those more or less approaching hatching (one cannot
say incubated in this case) are invariably more or less
mottled with white. Occasionally fairly fresh eggs are dug
out, bearing along their entire length on one side two parallel
white lines made apparently by the claws of the mother bird
when scraping the sand over them. The eggs are always a
little pointed towards one end, and some, especially the less
cylindrical ones, are conspicuously so. The shell is entirely
devoid of gloss, and the surface is everywhere roughened with
innumerable minute pores, which occur equally in the exterior
coloured flake and the white, somewhat less chalky, shell beneath.
In length the eggs vary from 3-01 to 3-4, and in breadth
from 1 9 to 2'2S ; but the average of sixty-two eggs that I have
carefully measured is 3'2S by 2'07-
THE FOLLOWING is a résumé of the dimensions of 15 specimens
measured in the flesh. The birds vary a good deal in size,
but this is probably due to age, and certainly not to sex, as some
of the largest and some of the smallest birds belonged to each
sex : —
Length, 14-5 to 17 ; expanse, 28 to 32-5 ; wing, 8 to 9'5 ;
tail from vent, 275 to 3'5 ; tarsus, 2'6 to 275 ; bill from gape,
1*2 to i'3 ; bill at front, 094 to i t ; wings, when closed, reach
from within one inch of, to quite the end of tail. In weight
they vary from 1 lb. 5 ozs. to 2 lbs. 2 ozs.
Legs and feet ; front of tarsus dark horny, in some greenish
horny ; scutae often irregularly marked with lighter horny ;
front of toes darker horny than tarsus, darkening still more
towards claws ; claws dark horny above, lighter horny beneath,
and tipped light horny ; soles pale carneous, sometimes pale
yellow ; tibio-tarsal articulation, back and sides of tarsi, dull
brick or litharge red ; bill light greenish or yellowish homy,
yellower along edge of mandibles ; lores and whole orbital and
aural region, and visible portions of the skin of the neck, showing
through between the sparse feathers, varying from a light,
somewhat dull, cherry red to a bright brick red ; irides light
brown or hazel brown.