228 
NAT U HAL HISTORY 
crop placed just upon the "bowels must, especially when full, 
be in a very uneasy situation during the business of incuba- 
tion ; yet the test will be to examine whether birds that are 
actually known to sit for certain are not formed in a similar 
manner. This inquiry I proposed to myself to make with 
a fern-owl, or goat-sucker, as soon as opportunity offered ; 
because, if their formation proves the same, the reason for 
incapacity in the cuckoo will be allowed to have been taken 
up somewhat hastily. 
Not long after a fern-owl was procured, which, from its 
tiabit and shape, we suspected might resemble the cuckoo 
in its internal construction. "Nor were our suspicions ill- 
grounded ; for upon the dissection, the crop, or craw, also 
lay behind the sternum, immediately on the viscera, between 
them and the skin of the belly. It was bulky, and stuffed 
hard with large Phalcence of several sorts, and their eggs, 
which, no doubt, had been forced out of those insects by the 
Action of swallowing. 
I^ow, as it appears that this bird, which is so well known 
to practise incubation, is formed in a similar manner with 
cuckoos, Monsieur Herissant^s conjecture — that cuckoos are 
incapable of incubation from the disposition of their intes- 
tines — seems to fall to the ground ; and we are still at a loss 
for the cause of that strange and singular peculiarity in the 
instance of the Guculus canorus.^ 
We found the case to be the same with the ring-tail hawk^ 
in respect to formation ; and, as far as I can recollect, with 
the swift ; and probably it is so with many more sorts of 
birds that are not granivorous. 
^ The cuckoo has no true crop, and the position of its proventriculus 
does not differ from that of other scansorial birds ; the oesophagus de- 
scends along the posterior or dorsal part of the thorax, inclining to the 
left side, and, when opposite to the lower margin of the left lung, it 
begins to expand into the glandular cavity or proventriculus. The giz- 
zard, which is neither large nor strong, is in immediate contact with the 
abdominal parietes, and not separated from them by an intervening 
stratum of intestines ; but this position cannot be supposed to interfere 
with the power of incubation, since it occurs also in other birds that do 
incubate. — Ed. 
^ This is a provincial name for the female Hen harrier, Circus cyaneus 
—Ed. 
