202 NATURAL HISTORY OF SELBORNE. 
OF) ge OF Oe Sel ae Ge. e 
TO THE SAME, 
SELBORNE, Afril 3rd, 1776. 
DEAR SIR,—Monsieur Herissant, a French anatomist, seems 
persuaded that he has discovered the reason why cuckoos do not 
hatch their own eggs; the impediment, he supposes, arises from 
the internal structure of their parts, which incapacitates them for 
incubation. According to this gentleman, the crop, or craw, of a 
cuckoo does not lie before the sternum at the bottom of the neck, 
as in the galine, colombe, &c., but immediately behind it, on and 
over the bowels, so as to make a large protuberance in the belly.* 
Induced by this assertion, we procured a cuckoo; and, cutting 
open the breast-bone, and exposing the intestines to sight, found 
the crop lying as mentioned above. This stomach was large and 
round, and stuffed hard, like a pincushion, with food, which, upon 
nice examination, we found to consist of various insects ; such as 
small scarabs, spiders, and dragon-flies ; the last of which we have 
seen cuckoos catching on the wing as they were just emerging out 
of the aurelia state. Among this farrago also were to be seen 
maggots, and many seeds, which belonged either to gooseberries, 
currants, cranberries, or some such fruit ; so that these birds appa- 
rently subsist on insects and fruits; nor was there the least 
appearance of bones, feathers, or fur, to support the idle notion of 
their being birds of prey. 
The sternum in this bird seemed to us to be remarkably short, 
between which and the anus lay the crop, or craw, and immediately 
behind that the bowels against the back-bone. 
It must be allowed, as this anatomist observes, that the crop 
placed just upon the bowels must, especially when full, be in a very 
uneasy situation during the business of incubation ; 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 pro- 
posed to myself to make with a fern-owl, or goatsucker, as soon as 
opportunity offered : because, if their formation proves the same, 
* Histoire de l’Académie Royale, 1752. 
