56 OBSERVATIONS ON THE CUCKOO. 
In this a great number of the membranes which had 
discharged yolks into the oviduct might be distinctly 
traced, and one of them appeared as if it had parted 
with a yolk on the preceding day. The ovarium still 
exhibited a cluster of enlarged eggs, but the most 
forward of them was scarcely larger than a mustard- 
seed. 
It plainly appears, Dr. Jenner remarks, that birds 
can keep back or bring forward their eggs (under 
certain limitations) at any time during the season ap- 
pointed for them to lay; but the Cuckoo, not being 
subject to the common interruptions, goes on laying 
from the time she begins till the eve of her departure 
from this country ; for, although old Cuckoos generally 
take their leave in the first week of July, yet instances 
are not wanting of eggs having been hatched so late 
as the middle of that month. 
Among the many peculiarities of the young Cuckoo, 
there is one which shows itself very early. Long be- 
fore it leaves the nest it frequently, when irritated, 
assumes the manner of a bird of prey, looks ferocious, 
throws itself back, and pecks at any thing presented 
to it with great vehemence, often at the same time 
making a chuckling noise like a young Hawk. Some- 
times, when disturbed in a smaller degree, it makes a 
kind of hissing noise, accompanied with a heaving 
motion of the whole body. 
Its chirp is plaintive, like that of the Hedge- 
Warbler ; but the sound is not acquired from the 
