INTRODUCTORY CHAPTERS. 13 
eves of the Blackbird. Sometimes the spots on them are very 
minute and multitudinous ; almost confluent from their number 
and minuteness ; sometimes large and well defined and permitting 
the ground-shade of the shell to be very apparent; sometimes 
reddish in colour, closely approaching the shade of those on the 
Ring-Ousel’s egg, and sometimes brown in hue, with no reddish 
tinge at all; and sometimes they disappear altogether, or very 
nearly, and leave the egg with a strong resemblance to the little- 
spotted Thrush’s egg.* ‘l'o such an extent is this the case, that 
a year or two since I was misled into assuming that four eggs 
which I found in a nest with all the characters of a Blackbird’s 
nest, must most certainly from their colour and markings, be as- 
signed toa Thrush original and not to a Blackbird. Other familiar 
instances of the same kind may be noticed as met with in 
the eggs of the House-Sparrow, the Tree-Pipit, the Sky-Lark, 
the Yellow-Hammer, one or more of the Hawks, &c. 
In the fabric and materials of nests, again, as constructed by 
birds of the same speciés, much dissimilarity, under peculiar 
circumstances, will be found to prevail. But really not more 
than might have been looked for beforehand, if it were not that, 
in our usual way of thinking about birds and other animals, 
we lay so much stress upon Instinct, and do not so much as 
admit to our notice the possibility that many of their actions 
may be prompted by a measure of intelligence, and not simply 
an unconsidering, unreasoning influence, which we term their 
Instinctive endowment. No doubt Instinct teaches them both 
to build and how to build their nests, and what materials are the 
most suitable, and the sites that are most eligible. But it is 
scarcely Instinct which sets the Eagle and the Crow, when their 
abode is in a place that does not furnish the sticks they commonly 
* Yarrell, i. 204. Hewitson, i, 63. 
