INTRODUCTION. 
• • 
Vll 
I have elsewhere noticed the assiduity with which the Eider 
Duck covers its eggs. 
Many of the smaller birds will allow themselves to be taken 
in the hand, rather than leave their nests. Some have been 
even known, upon having their young ones taken from them, 
to follow them into captivity. 
The obstinate perseverance with which the Blue Titmouse 
continues to rebuild its nest, although it has been repeatedly 
destroyed, is very remarkable; and still more so the pertina¬ 
city with which it continues to sit its eggs, in defiance of all 
intrusion; and to retain possession of the hole in which they 
were placed, sometimes for days after they have been taken 
from it. 
Notwithstanding the numerous accounts we hear of the 
fecundity of some of our smaller birds, I am much inclined to 
think that their powers of incubation have been overrated, 
and that the usual number of eggs only, which it is allotted 
them to lay, are sufficiently developed to be brought to ma¬ 
turity at one time. Those birds, however, which under ordi¬ 
nary circumstances would only breed once a year, have never¬ 
theless, if deprived of their eggs, the power of producing, a 
short time afterwards, a second and even a third set; but 
usually diminished in their numbers, as well as in their size. 
That the colouring of birds’ eggs is an animal matter, and 
dependent upon the health of the bird, there can be little 
doubt. The day previous to the eggs being produced, and after 
the shell has become hard, they are, in those birds which I 
have examined, pure white; a large proportion of the colour 
is also easily rubbed off, for some time after they have been 
laid. Thus we find in their eggs the same want of colour, 
which is also occasionally observable in the feathers of white 
varieties of birds. Fear, or any thing which may affect the 
animal functions, exerts its influence upon the colour also. 
The eggs of birds which I have captured on their nests, 
during the time that they were laying, and kept in close con¬ 
finement, have thus been deprived of much of their colour. 
