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Mr. W. P. Pycraft,



IV. Comparison of Fraser’s Touracou with the

Cuckoos.


The Touracous are regarded, with almost common con¬

sent, by systematists, as more nearly allied to the Cuckoos than

to any other group : and this attitude may be regarded as sound.


It is well therefore that we should briefly compare the

young stages of these two birds.


As we have already pointed out, the young of both groups

have been stated to agree in that they remained naked until the

feathers break their sheaths.


We now know that the young of the Touracous, on the

contrary, are clothed in down during the early stages of life.


The Cuckoos are generally regarded as having young

which do not develop nestling down but remain naked till the

feathers appear. Thus, though at first naked, they soon present

a curiously spiny appearance, recalling that of the hedgehog,

and this is retained till the bursting of the feather sheaths.


We have yet much to learn concerning the Cuckoos, how¬

ever. It is certain that the young Touracous represent the more

primitive condition. And it would seem that the Cuckoos have

become highly specialized in this matter, the nestling down,

from some reason not yet understood, having become suppressed.

The young of Ce?itropus—the Lark-heeled Cuckoos—however yet

preserve traces of the nestling down, which appears during

late embryonic life in the form of long slender threads. These, on

hatching, retain this peculiar form until borne out, after the

fashion of nestling down, on the tips of the developing contour

feathers. These hair-like structures are to be regarded as

vestiges of the nestling down feathers which never burst their

investing sheaths.


Whilst the young Cuckoos are completely zygodactylous,

the young Touracou is only partly so.


V. Comparison of the Nestling Touracou with the

Nestling Hoatzin ( Opisthocowms cristatusj.


We may now pass on to compare the young Touracou

with the young of that aberrant and extremely interesting bird

the Hoatzin, Opisthocomus cristatus.



