66 OBSERVATIONS ON THE CUCKOO. 
ones, which chiefly sustain her weight, and, conse- 
quently, are less liable to be moved, usually remain 
unmolested. When the eggs of birds are exchanged 
for others of a uniform magnitude, whether larger or 
smaller than their own, provided the difference is not 
so great as to occasion them to be forsaken, no dis- 
turbance ensues, whatever their colour may be, the 
change either not being perceived or totally disre- 
garded; and the young, when extruded, are attended 
with the utmost care and solicitude. 
Cuckoos generally use the precaution of waiting for 
the absence of small birds from their nests before 
they venture to lay in them: sometimes, however, 
their approach is perceived, when the owners imme- 
diately make every effort to repel them, but do not 
always succeed, as the following instance evinces. 
On the evening of the 24th of June, 1814, I saw a 
hen Cuckoo alight in a field of mowing grass, when 
a pair of Titlarks attacked it with such fury that they 
pulled several small feathers off it. Their loud cries 
and violent gesticulations attracted the notice of 
several people at work near the spot, who, by throw- 
ing stones at the Cuckoo, drove it to some distance ; 
however, it soon returned, and, though repeatedly 
annoyed, persevered till it ultimately accomplished its 
purpose by laying in the nest of the Larks. As this 
bird was on the very eve of its departure (for I did 
not see a single old Cuckoo that year after the 25th 
of June), the case was an urgent one, and may account 
