84 MR. W. J. F. WILLIAMSON ON 
There appears to be no very definite information available as to 
the usual complement of eggs laid by the eastern form of S. bergii, and 
the only notes on the subject, which I have been able to trace, are all very 
old ones. Butler (op. cit. supra), in describing his personal visit to 
Astolah Island, off the Mekran coast, Baluchistan, on 29th May 1877, 
states that he obtained 93 eggs in one day, all laid singly. On the other 
hand, a large batch collected for him about three weeks later, by (ap- 
parently) a native of the locality, were said by the man to have been 
“usually three in each nest.”! This statement is quoted by Hume 
without comment, but it cannot, I think, be given any credence. It is 
true that Butler, in speaking of his own find, says that the number of 
eggs was “at that time only one............... to each pair of birds”’— 
thus implying that, at a later date, the number of eggs might have 
been increased, but apparently he himself never found more than one. 
On the other hand, it is to be noted that Captain Shopland (also quoted 
by Hume), who took eggs near Akyab, states that some of them were 
in pairs, though he does not give any figures. 
My observations would seem to show that Siamese birds 
usually lay a single egg, but that occasionally there are two in a 
clutch. 
STrERNA MELANAUCHEN. The Black-naped Tern. 
As regards S. melanauchen, I obtained 37 single eggs and 26 
pairs in 1917--all of them quite fresh. About a week later, I 
had 4 single eggs and 3 pairs sent to me by a reliable European 
friend from a small islet near Koh-Si-Chang (in the same neighbour- 
hood), all of which were more or less incubated. The number pro- 
cured on the second occasion is somewhat small, but the proportion of 
double eggs to single ones is almost exactly the same as that of the 
very much larger number obtained by me, viz., about 41 or 42 per cent. 
of the total assignable to each pair of birds. In 1918 I obtained very 
few eggs of this species, which appears to lay somewhat later 
than 8S. bergii and S. anestheta-—the actual number collected being 8 
singles and 5 pairs. Osmaston [Journ. Bombay N. H. S8., XVII 
(1906), p. 491] in writing of Andaman birds, observes that they lay 
“one or two eggs.” This remark appears to be correct, as far as it 
goes. In Siam, I should say, about half the clutches contain two eggs, 
and the remainder one only. 
JOURN. NAT. HIST. SOC. SIAM. 
