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 Eook 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 that 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 then’ 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 
case 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 even reared 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 puc 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 
