50 BRITISH BIRDS, WITH THEIR NESTS AND EGGS. 
Mr. Bidwell’s study of the habits of this bird has led him to the conclusion 
that it lays five eggs in a season at intervals of seven or eight days. It is not 
at all improbable that this may sometimes be the case, but Mr. Harper’s experience 
quoted above seems to show that the habit is not invariable; moreover, as recorded 
in my ‘‘ Handbook” (p. 103) a friend of mine took five eggs in one evening, all 
so much alike that, presumably, they represented the clutch of one bird, in a 
swampy grove at the village of Tong, near Sittingbourne, and all from nests of 
the Sedge Warbler: none of these eggs were much incubated, indeed they were 
all blown with ease, so that there could have been no such interval between the 
dates at which they were deposited. 
It is extremely probable that five represents the normal clutch of the Cuckoo, 
and Mr. Rowley’s studies led him to the conclusion that the time of nidification 
extended from the beginning of May to the middle of July, but in Kent I have 
only found the eggs from the middle of May to the end of June. 
As a rule the eggs of this bird are coloured and marked much like eggs of 
the Pied Wagtail, the Greater Whitethroat, pale varieties of the Sky-Lark, etc., but 
sometimes they greatly resemble the eggs with which they are deposited, even 
when the latter are utterly dissimilar from the normal type: thus I took a clutch 
of Robin’s eggs containing that of a Cuckoo remarkably resembling those of the 
foster-parent, whilst Seebohm, William Borrer, of Cowfold, Sussex, and others have 
taken pure blue eggs deposited with those of the Hedge-Sparrow, Redstart, etc.* 
In almost all eggs of the Cuckoo there are tiny rounded slate-coloured spots 
towards the larger end, although in blue eggs these spots are frequently almost 
obsolete. 
Of the eggs figured on pl. vill, figs. 266, 271, 272, 275, 276, 278, 280, 283, 
284, 285, 286, and 288 are from Mr. A. B. Farn’s collection; 270, 274, 277, 279, 
287, and 289 are from my own series, and 273, 281, 282 from that of Mr. Frohawk. 
In the fine series which we have figured, it will be seen that the egg varies 
remarkably even when deposited in nests of the same species, and generally, when 
placed in a Hedge-Sparrow’s nest, they are so little like those laid by that bird, 
as to make one wonder that they are not ejected. 
It has been suggested, as an explanation of the fact that the eggs of the 
Cuckoo sometimes resemble those of its foster-parents, that the parents for gen- 
erations past had been reared by the same species, and that the similar feeding 
and treatment had in some inexplicable manner affected the deposition of pigment. 
If this be a fact it is no marvel if these assimilations are rare, for it would seem 
to necessitate a condition of things which is well nigh impossible, viz:—that both 
* From one of these Seebohm extracted a young Cuckoo, recognizable at once by the character of its feet. 
