PARASITISM OF CUCKOOS 
actually does is broadly this. The eggs are produced 
rather continuously, so that the bird could not very 
well place them all in one nest and then proceed to the 
duties of incubation. The process would be too long 
for the life of the parent. Thus it has had recourse 
to its well-known habit. In accordance with the varied 
hospitality upon which the cuckoo insists, the eggs vary 
greatly in colour ; but whether there is always a cor- 
respondence between the nest selected and the colour 
of the eggs laid therein is not so certain. It has been 
suggested that individual cuckoos acquire the habit of 
laying their eggs in the nests of a given species, or even 
for a series of seasons in the nests of the same individual. 
That therefore the eggs, by a process of elimination, 
get to be like those of the adopted foster parent, and 
that the variety of egg coloration in the cuckoo is a 
matter of individual cuckoos, and not individual eggs 
of the same cuckoo. It is furthermore plain that the 
young cuckoo is stronger and more muscular than its 
fellow nestlings and that it actually does forcibly eject 
them. But this predatory instinct on behalf of its 
young is not universal in the cuckoo tribe. All the 
immediate allies of the Cuculus canorus of our islands 
are parasitic. But Eudynamis is the one exception 
apparently among the group of cuckoos to which it 
belongs that shows this characteristically cuculine habit. 
This shows of course that the habit is but a recent one, 
a point of view that issupported by the rare occurrence 
(one case at any rate has been authenticated), of 
common cuckoos building a nest of their own, and 
attending to their own offspring The lark-footed 
cuckoo (Centropus), usually to be seen in the Zoo, is not 
parasitic. Now it is interesting that this cuckoo, like 
some others which are equally independent of the 
assistance of other birds, lays a white egg. The para- 
sitic species have apparently all of them spotted and 
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