VARYING FECUNDITY IN BIRDS. 497 
regularly have a second nest. IJt is not, I think, difficult to see 
why they respectively lay their five and ten eggs a season, and 
“neither more nor less. ‘These birds, resident and migratory 
alike, feed their young on various forms of insect-life—flies, 
grubs, aphides, the smaller kinds of caterpillars, and the ova of 
these insects. The two parent birds would be unequal to catering 
for the wants of a larger brood than five; neither could a hen of 
this size well produce more than five eggs. Indeed, four is not 
an uncommon clutch by any means in districts where insect-food 
is not specially abundant. On the other hand, a Blackcap 
Warbler must produce five young in a season to prevent her 
species diminishing ; and as the breeding season is curtailed by 
migration, which the young must be old enough to undergo when 
the time arrives, we see that a smaller clutch would not be con- 
venient. The resident small birds, however—F inches, Buntings, 
&c.—are not hampered by the approach of the period of migra- 
tion, and they indulge in a second brood. It is necessary for 
them to produce eight or ten of their kind in a season to aid in 
killing off from the cultivated lands the vast swarms of insects to 
which the summer has given birth, and which the efforts of the 
parents when feeding have proved utterly inadequate to cope 
with. Although the Finches thus produce four or five times 
their own number, yet by the next spring each family of Finches 
will usually have dwindled down to a pair once more; for what 
the birdcatcher spares, God and the winter take. 
2. Tue Tits anp THe Wren, — These birds during the 
season feed on a very similar diet to those described under 1, 
and they lay from six to twelve eggs in each nest, though one 
cannot say definitely how often they have a second brood. Still, 
taking into consideration the number of Finches’ nests that 
the small boys destroy, I should be inclined to say that the Tits 
rear more young than the Finches. They are not the prey of 
the birdcatcher, who annually robs our woods and fields of tens 
of thousands of Finches. Why then are they so prolific? 
Simply because they feed mainly on an insect diet all the year 
round, and in the depth of winter insect-food is scarce and 
difficult to obtain. I have found a score of Tits lying dead on 
the snow in a single walk in a winter that was not specially 
severe, All were dead from starvation, not from cold; their 
