Journal of Proceedings. xcv
unpleasant task, as we should consider it, of rearing the offspring of
another species. Some years ago the question occurred to me " How far
may this sort of thing be carried ?" and in the summer of 1876 I com-
menced a series of experimental interchanges among the eggs and young
of the various common birds nesting near our house. This I did partly
to satisfy a mere curiosity and partly to see whether I could throw some
light on the willingness of one species to rear the young of another, as is
the case with the young English Cuckoo and some other allied species.
Of course in making these exchanges I had to take those obviously
necessary precautions which I believe the Cuckoo itself invariably takes.
Thus it would have been plainly absurd to place the egg of a Domestic
Fowl among those of a Hawk or vice versa, or those of a Book among
those of a Partridge, and it would have been equally ridiculous to
exchange the eggs of a Starling for those of a Tit or vice versa, or those
of a Pigeon for those of a Thrush. In short I did not think it worth my
while to effect any exchanges, either among eggs or young, unless the
two species concerned approached each other more or less closely in
regard to habits, food, and size. I may add chat I never attempted to
interchange the egg of any bird that is hatched fully formed, with its
eyes open and able to run or swim and feed itself (called " Hesthogens,"
by Ed. Newman), with those of any other bird whose young is hatched,
generally, in an elaborate nest in a tree, blind, helpless, naked, and
unable to feed itself (styled " Gymnogens," by the same writer).
But few will need to be told that in one form this interchanging of
eggs and young is a thing of everyday occurrence on any farm. The
henwife thinks nothing of making a Hen hatch the eggs of a Duck, and
even rear the aquatic young, while Turkeys may be set to rear young
Geese without their expressing any particular objections. Every game-
keeper, too, is accustomed to place the eggs of the Partridges and
Pheasants, that are mown over in haytime, under a hen to hatch. But
there are cases on record in which this system of adoption seems to have
been carried out voluntarily by both wild and tame birds. It is not very
unusual to read of instances in which two different species have laid
eggs together in the same nest. This seems to be more especially the
ease among some game birds than with others. Two Pheasants or two
Partridges, or even a Pheasant and a Partridge, have not very
unfrequently been known to do the same thing, while in Morris's
' British Birds ' an extraordinary case is mentioned, in which a Common
Buzzard, which had been kept some years in confinement, evinced, by
constructing a nest of straw, a great desire for incubation, and on being sup-
plied with Hen's eggs, sat upon, hatched, and evenreared them. Doubtless
a search into Natural History literature would reveal other instances,
but I will here confine myself simply to recounting my own experiments.
My first attempt was on June 14th, 1876, when, finding a half-
grown sparrow that had fallen from its nest, and was nearly dead
with cold and hunger, I put it into a nest in which a Blackbird was
sitting on four almost fresh eggs. On the 19th the Sparrow had grown
and flourished famously, having been fed by the Blackbird at the expense
of its own eggs, which, all except one, had disappeared. It left the nest
on the 21st, as well as if it had been brought up by its own parents. At
the end of the month I put some hard-sat Martin's eggs into a Swallow's
nest in exchange for some of her own. They were hatched on the 4th
of August, and successfully reared, as might have been expected from
the similarity of the two species. At the end of June, 1877, I placed a
Sparrow's egg in the nest of a Spotted Flycatcher, which afterwards laid
some more of her own eggs without taking any notice of the stranger,
but soon after the nest got taken. About the same time I interchanged
a young Yellowhammer for a young Blackheaded Bunting. Both were