A Cooperative Stmljj 
311 
reduced, 1914 was a splendid contrast to 1913: never were so many birds seen 
and the young were as abundant as the eggs. At first sight it seemed strange to 
find such a flourishing colony after the comparative failure of the previous year, 
but in the summer of 1914 the channel was phosphorescent at night with Plankton, 
and probably as a result of this the channel was also swarming with myriads of 
" Whitebait," which in their turn attracted the Terns. The suggestion is thus 
thrown out that a plentiful food supply increases the size of the eggs. It must, 
however, be borne in mind that possibly only the stronger and bigger birds survived 
the previous bad season. There may have been fewer very young or very old birds 
and thus the eggs larger. 
We may now consider the variabilities of the two years. 
TABLE 11. 
Character 
Standard Deviation 
CoetKcient of Variation 
1913 
1914 
1913 
1914 
Length L 
Breadth B 
Longitudinal (lirth Gi ... 
Transver.se Girth O'l, 
Index my BjL 
Index of Ovahty 0 
•180+ -035 
■099+ -010 
•376 + ^010 
•347 + -010 
3- 449 + -096 
4- 334+ ^121 
■18,5 + -003 
■099 + -001 
•350+ 005 
•300 + -004 
3^479 ± -0.50 
4^32(j±^062 
4-34+ -12 
3 33+ 09 
3-.30 + 09 
3-62 + -10 
[4-79 + -13]* 
[7-69 + ^22] 
4-39 ± -006 
3-28 + -005 
3^03 + -005 
3^10+ -005 
[4-84 + •069]* 
L7^75fni] 
The table indicates that the material for 1914 is slightly less variable than 
that of 1913 taken as a whole. This is possibly due as we have suggested bo the 
bad season of 1913 reducing the number of very young or very old birds and so the 
small eggs in 1914. But most of the differences are insignificant except those in the 
two girths. W^e anticipate that a good deal of interest from the evolutionary stand- 
point might be reached by secular observations on the eggs of this tern colony, 
taken in conjunction with records of the food supply and climate both in the 
nesting season and after. It would be of interest also to mark certain birds and 
record if possible their return. 
(3) Associations of Nest and Egg Pattern. 
It is of great interest to discover whether there is any protective action in the 
colouring and mottling of the egg. In an egg which varies in itself so largely as 
the tern's this question must be considered not so much in regard to the general 
nesting habits of the species, but in regard to the nest and environment of each 
individual bird. The occasional and possibly habitual practice (see our ftn. 
p. 308) of laying and nest building simultaneously may indeed suggest that the 
birds adapt the immediate environment and material of the nest to the actual 
* See remarks, footnote f, p. 147 of previous paper. 
