C U C U L U S. 
the cuckoo to take charge of its young one ; but, as it is 
a bird lefs familiar than many that I have mentioned, its 
ned is not fo often difcovered. I have, neverthelefs, 
had feveral cuckoo’s eggs brought to me that were found 
in titlarks’ nefts, and had one opportunity of feeing the 
young cuckoo in the neft of this bird. I faw the old 
birds feed it repeatedly ; and, to fatisfy myfelf that they 
were really titlarks, fhot them both, and found them to 
be fo. 
“ Example 2 . A cuckoo laid her egg in a water-wag¬ 
tail’s neft in the thatch of an old cottage. The wagtail 
fat her ufual time, and then hatched all the eggs but 
one ; which, with all the young ones except the cuckoo, 
was turned out of the neft. The young birds, confiding 
cf five, were found upon the rafter that projected from 
under the thatch, and with them was the egg not in the 
lead injured. On examining the egg, I found the young 
wagtail it contained quite perfect, and juft in fuch a date 
as birds are when ready to be difengaged from the fhell. 
The cuckoo was reared by the wagtails till it was nearly 
capable of flying, when it was killed by an accident. 
“ Example 3. A hedge-fparrow built her neft in a 
hawthorn bufh in a timber-yard. After fhe had laid two 
eggs, a cuckoo dropped in a third. The fparrow conti¬ 
nued laying as if nothing had happened, till lhe had laid 
five, her ufual number, and then fat. June 20, 1786. 
On infpefting the neft, (fays Mr. Jenner,) I found that 
the bird had hatched this morning, and that every thing 
but the young cuckoo was thrown out. Under the neft 
I found one of the young hedge-fparrows dead, and one 
egg by the fide of the neft entangled with the coarfe 
woody materials that formed its outfide covering. On 
examining the egg, I found one end of the fhell a little 
cracked, and could fee that the fparrow it contained was 
yet alive. It was then reftored to the neft, but in a fevr 
minutes was thrown out. The egg, being again fuf- 
pended by the outfide of the neft, was faved a fecond 
time from breaking. To fee what would happen if the 
cuckoo was removed, I took out the cuckoo, and placed 
the egg containing the hedge-fparrow in the neft in its 
ftead. The old birds, during this time, flew about the 
fpot, (hewing figns of great anxiety ; but, when I with¬ 
drew, they quickly came to the neft again. On looking 
into it in a quarter of an hour afterwards, I found the 
oung one completely hatched, warm, and lively. The 
edge-fparrows were buffered to remain undifturbed with 
their new charge for three hours, (during which time 
they paid every attention to it,) and then the cuckoo 
was again put into the neft. The old fparrows had been 
fo much difturbed by thefe intrufions, that for fome time 
they (hewed an unwillingnefs to come to it. However, at 
length they came ; and on examining the neft again, in a 
few minutes, I found the young fparrow was tumbled 
out. It was a fecond time reftored, but again expe¬ 
rienced the fame fate. From thefe experiments, (conti¬ 
nues Mr. Jenner,) and fuppofing, from the feeble ap¬ 
pearance of the young cuckoo, juft difengaged from the 
fhell, that it was utterly incapable of difplacing either 
the egg or the young fparrows, I was induced to believe 
that the old fparrows were the only agents in this feem- 
ing unnatural bufinefs. But I afterwards clearly per¬ 
ceived the caufe of this ft range phenomenon, by difco- 
vering the young cuckoo in the aft of difplacing its fel- 
low-neftlings, as the following relation will fully evince. 
“ June 18, 1787, I examined the neft of a hedge-fpar¬ 
row, which then contained a cuckoo’s and three hedge- 
fparrows’ eggs. On infpefting it the day following, I 
found the bird had hatched, but that the neft now con¬ 
tained only a young cuckoo and one young hedge-f parrow. 
The neft was placed fo near the extremity of a hedge, 
that I could diftinftly fee what was going forward in it ; 
and, to my aftonifhment, faw the young cuckoo, though 
fo newly hatched, in the aft of turning out the young 
hedge-fparrow. The mode of accomplilhing this was 
very curious. The little animal, with the afliftance of 
435 
its rump and wings, contrived to get the bird upon its 
back ; and making a lodgment for the burden by elevat¬ 
ing its elbows, clambered backward with it up the fide of 
the neft till it reached the top ; where, refting for a mo¬ 
ment, it threw oft' its load with a jerk, and quite difen¬ 
gaged it from the neft. It remained in this fituation a 
fhort time, feeling about with the extremities of its wings, 
as if to be convinced whether the bufinefs was properly 
executed, and then dropped into the neft again, With 
thefe (the extremities cf its wings) 1 have often fee 11 it ex¬ 
amine, as it were, an egg and neftiing before it began its 
operations ; and the nice fenlibility which thefe parts ap¬ 
peared to poffefs, feemed fufficiently to compenfate the 
want of fight, which as yet it was deftitute of. I after¬ 
wards put in an egg ; and this, by a fimilar procefs, was 
conveyed to the edge of the neft, and thrown out. Thefe 
experiments I have fince repeated feveral times in diffe- 
rent nefts, and have always found the young cuckoo dif- 
pofed to aft in the fame manner. In climbing up the 
neft, it fometimes drops its burden, and thus is foiled in 
its endeavours; but, after a little refpite, the work is 
refumed, and goes on almoft inceftantly till it is effedted. 
It is wonderful to fee the extraordinary exertions of the 
young cuckoo, when it is two or three days old, if a bird 
be put into the neft with it that is too weighty for it 
to lift out. In this ftate it feems ever reftleis and un- 
eafy. But this difpofition for turning out its companions 
begins to decline from the time it is two or three till it 
is about twelve days old ; when, as far as I have hitherto 
feen, it ceafes. Indeed, the difpofition for throwing out 
the egg appears to ceafe a few days fooner ; for l have 
frequently feen the young cuckoo, after it had been 
hatched nine or ten days, remove a neftiing that had been 
placed in the neft with it, when it fuffered an egg, put 
there at the fame time, to remain unmolefted. The An¬ 
gularity of its fhape is well adapted to thefe purpofes ; 
for, different from other newly-hatched birds, its back,, 
from the fcapulae downwards, is very broad, with a con- 
fiderable depreftion in the middle. This depreflion 
feems formed by nature for the defign of giving a more 
fecure lodgement to the egg of the hedge-fparrow or its 
young one when the young cuckoo is employed in re¬ 
moving either of them from the neft. When it is about 
twelve days old, this cavity is quite filled up, and then 
the back a flumes the fhape of neftiing birds in general. 
“Having found that the old hedge-fparrow commonly 
throws out fome of her own eggs after her neft has re¬ 
ceived the cuckoo’s, and not knowing how fhe might 
treat her young ones if the young cuckoo was deprived 
of the power of difpoflefling them of the neft, I made 
the following experiment : 
“July 9. A young cuckoo, that had been hatched 
by a hedge-fparrow about four hours, was confined in 
the neft in fuch a manner that it could not poflibly turn 
out the young hedge-fparrows which were hatched at 
the fame time, though it was almoft inceftantly making; 
attempts to effeft it. The confequence was, the old 
birds fed the whole alike, and appeared in every relpeft 
to pay the fame attention to their own young as to the 
young cuckoo, until the 13th, when the neft was unfor¬ 
tunately plundered. 
“The fmallnefs of the cuckoo’s egg, in proportion to 
the fize of the bird, is a circumftance that hitherto, I 
believe, has efcaped the notice of the ornithologift. So 
great is the difproportion, that it is in general (mailer 
than that of the houfe-fparrow ; whereas the difference 
in the fize of the birds is nearly as five to one. I have 
ufed the term in general, becaufe eggs produced at dif¬ 
ferent times by tlie fame bird vary much in fize. I have 
found a cuckoo’s egg fo light that it weighed only forty- 
three grains, and one fo heavy that it weighed fifty-five 
grains. The colour of the cuckoo’s eggs is extremely 
variable. Some, both in ground and penciling, very 
much refemble the houfe-lparrow’s; fome are indiftinftly 
Covered with bran-coloured fpots ; and others are mark- 
s el 
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