APPENDIX 
WEIGHTS OF CUCKOO A’s EGGS 
I am indebted to Mr. P. F. Bunyard of Croydon for the kind 
trouble he has taken to weigh accurately the empty shells of 
each of the 61 eggs collected from Cuckoo A during the four 
seasons 1918-1921. The weights, given below, for 1920 and 
1921 have, perhaps, the greater scientific interest, as we know 
that the whole of the eggs laid in those two seasons are included, 
that each was fresh when taken, and there is no doubt whatever 
as to the order in which they were laid. 
Attention may be drawn to a few interesting points : — 
• (i) The first egg laid in each of the seasons 1920 and 1921 
is considerably the lightest of its series. 
(ii) The last eggs laid in the years 1919 and 1920, when the 
Cuckoo was encouraged to lay to the extreme limit of her powers, 
show a striking drop in weight in comparison with the eggs laid 
immediately before. The last egg of 1919 was 14 milligrammes 
lighter than the last but one ; the last of 1920 15 milligrammes 
lighter. 
(iii) This fact is the more interesting when contrasted with 
the fact that in 1921, when the Cuckoo was, according to my 
theory, discouraged from laying as many as she could have laid 
if further “ natural fosterer ” provision had been made for her, 
the last egg laid was actually heavier than that season’s average 
(196*6 milligrammes), and very little lighter than its immediate 
predecessors. 
23X 
