events. There is abundant proof that the time of its insertion
is very variable. It may he deposited before the owner
of the nest has laid any egg of her own, or after she has
completed her clutch. Several authorities have declared that
the Cuckow’s egg needs not so long a period of incubation
as the eggs of most of the birds upon which its care is
imposed; hut this is a matter that must at present he
deemed undecided.* In due time it is hatched, and then
takes place one of the most wonderful things in the whole
history of this wonderful bird; for the discovery of which we
are indebted to the accurate observations of the celebrated
Edward Jenner, as related by him in a letter to John Hunter,
by whom they were communicated to the Eoyal Society
(Phil. Trans. 1788, pp. 219-237). So strange a chapter of
Natural History had never before been published, and it is
by no means surprising that some of the contemporaries of
those great men hesitated to credit what they therein read.
Jenner’s account of what he saw has, however, been fully
confirmed by later experience, and exception can only be
taken to some minor details of which it was impossible for
him to assure himself.t It had of course been commonly
known for centuries that very soon after the Cuckow was
having been found in the nests of the following species though not necessarily
in the British Islands :—all the Shrikes; the Spotted Flycatcher ; the Golden
Oriole; the Song-Thrush, Mistletoe-Thrush (Zool. Garten, 1878, p. 177), Blackbird,
Ring-Ouzel and Rock-Thrush ; the Sylviidce except the Rufous, Savi’s and
the Yellow-browed Warbler; the Wren; the Treecreeper; the Great Titmouse
; all the Wagtails and Pipits ; the Larks except the Shore- and the Whitewinged
Lark ; the Reed-, Great, Yellow and Cirl-Bunting and the Ortolan;
the Chaffinch and Brambling, the Tree- and House-Sparrow, the Hawfinch
and Greenfinch, the Serin, the Linnet and Mealy Redpoll and the Bullfinch ;
the Swallow; the Daw, Pie and Jay ; the Ring-, Stock- and Turtle-Dove ; and,
most strange of all, the Little Grebe (Journ. fur Ornith. 1876, p. 391)! But
of these birds, seventy-eight in number, four—the Hedge-Sparrow, Reed-
Warbler, Pied Wagtail and Meadow-Pipit, deserve particular notice as being
those most commonly chosen as foster-parents.
* Thus Jenner, in the course of his observations immediately to be mentioned,
thought that the Cuckow’s egg is usually hatched first, but he knew of one
instance to the contrary (p. 228, note).
•(• For instance where he states'(p. 221) that the Cuckow’s dupe “ whilst she is
sitting, not unfrequently throws out some of her own eggs, and sometimes
injures them in such a way that they become addle.”
hatched the eggs or young, if such there were, of its fosterparent
disappeared from the nest, of which the interloper
remained the sole tenant, but th e«way in which they were
got rid of was wholly unsuspected until ascertained by
Jenner. Some people believed with Lottinger that the
parent Cuckow was the author of their destruction,* others
supposed that they were smothered by the disproportionate
size of their fellow-nestling and their corpses cast out by their
own parents. By a succession of experiments, the particulars
of which it is here impossible to give, Jenner learnt that the
young Cuckow, alone and unaided, was the agent, and it was
in June 1787 that he ascertained this fact. On the 18th of
that month he examined a Hedge-Sparrow’s nest, which
then contained a Cuckow’s egg and three eggs of its owner.
Inspecting it the next day he found therein a young Cuckow
and a young Hedge-Sparrow, and as it was so placed that
he could distinctly observe what went on in it, he, to his
astonishment, saw the former, though so lately hatched, in
the act of turning out its companion:—
“ The mode of accomplishing this was very curious. The
little animal with the assistance of its rump and wings,
contrived to get the bird upon its back, and making a lodgement
for the burden by elevating its elbows, clambered backward
with it up the side of the nest till it reached the top,
where resting for a moment, it threw off its load with a jerk,
and quite disengaged it from the nest. It remained in this
situation a short time, feeling about with the extremities of
its wings, as if to be convinced whether the business was
properly executed, and then dropped into the nest again.
With these (the extremities of its wings) I have often seen
it examine, as it were, an egg and nestling before it began
its operations ; and the nice sensibility which these parts
appeared to possess seemed sufficiently to compensate the
want of sight, which as yet it was destitute of. I afterwards
put in an egg, and this, by a similar process, was conveyed
to the edge of the nest, and thrown out. These experiments
* Yet in 1782 Lottinger himself had personal proof of the expulsion of an
egg from the nest by a young Cuckow (Hist, du Coucou d Europe, p. 18).