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VARYING FECUNDITY IN BIRDS. 
By Basi Davies. 
Mr. WarveE Fow ter, in one of his bird stories, describes the 
uneasiness of a youthful hen Wagtail when she began to ponder 
on the question, ‘“‘ Why do we wag our tails ?’’—the moral being, 
I suppose, that facts come before reasons for facts, and ought to 
suffice for most of us. Checked somewhat by this allegory, my 
ideas on the above subject received a fresh impetus when, in 
‘Summer Studies of Birds and Books,’ I read that Mr. Warde 
Fowler actually felt it his duty to ask and to attempt to answer 
that very same question which used to trouble his little hen 
Wagtail. Ihave no apology of duty to offer for my poor attempts 
at explanation: I can only say that the subject is one to which 
very little attention has been given, and that it is one in which 
a really skilful ornithologist could probably make most successful 
researches. ‘ 
The ordinary birdsnesting naturalist regards an abnormal 
clutch, whether large or small, only with a view of its suitability 
for his collection. He robs a Nightingale of five eggs and a 
Partridge of fifteen without attempting to explain why the off- 
spring of the one species is numerically so superior. Some 
years ago, reviewing my season’s “take” of eggs, I felt myself 
somewhat of a monster when I imagined the table on which my 
cases lay peopled with those birds whose embryos I had removed 
from every shell—six Nightingales, a dozen Bullfinches, and so 
on—though I never took more than one egg from anest. Con- 
sequently, in abandoning collection, I sought for a new interest 
in eggs to take its place; and this chapter is an endeavour 
to explain the interest of a different sort that I now take in the 
nests I find. 
There are certain general principles which it is well to keep 
in mind in this particular branch of bird-study. Such is the 
rule, that birds do not merely breed so many times a year in the 
course of nature, but that they feel it their duty not only to 
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