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[Vol. 11-No. 11 


rest of this order lays eggs with a well-developed 
ground tint, and usually richly covered with dark 
coloured markings. 
2. Eggs covered by the parent bird with leaves or 
other vegetable matter. 
There is no doubt but that a loss of pigment has 
resulted from this mode of concealment. It is in- 
teresting to speculate on the reasons which have 
led certain birds which breed on the ground to 
adopt this method of protection, whilst others 
trust to the colour of the eggs. In the Grebe 
tribe it seems the only method possible. Protec- 
tective coloration of the eggs would be a much 
less effective mode when they are deposited on 
the top of a large and prominent heap of decay- 
ing water plants; and it would be impossible for 
them, on account of their peculiar wings and 
legs, to escape from the nest unless it were close 
to the water’s edge. ‘‘It would seem that what- 
ever they do must be done in the water,” writes 
Naumann; “ they cannot even rise upon the wing 
without a preliminary rush over the surface of the 
lake; from dry land they cannot commence their 
flight.” The loss of pigment is complete in the 
Grebes, as it is probable that the wet decaying 
vegetation shuts out the light more completely 
than the loose dry materials employed by the 
Ducks, Pheasants, &e. 
In the duck tribe this method has probably 
been adopted because of the size and large number 
of eggs laid. Protective coloration could not 
have afforded sufficient concealment. for eight or 
ten or even more large eggs. The amount of de- 
colorisation varies in this tribe. In some in- 
stances, as the Eider Duck, the egg is of a pale as- 
paragus green, in others it has only a very faint 
greenish hue, whilst in the Sheldrake, which 
breeds in holes, the loss of pigment is complete ; 
the egg being of a “smooth shining white.” 
In both the above groups the whole of the fami- 
ly adopt the same mode of concealment, but why 
should the eggs of the Pheasants and Partridge be 
covered, whilst those of the Grouse are laid 
openly? The two former birds breed in sheltered 
woods and hedgerows, the latter on bleak and ex- 
posed moors. If the Grouse covered its eges with 
dead vegetable material it would soon be carried 
away by the strong winds which sweep over the 
moors. 
3. Eygs covered by an incrustation of calcareous 
matter. 
Only three British birds’ eggs are coated with 
this peculiar chalky substances, viz., the Cormo- 
rant, the Shag and the Gannet. The hard sheli 
beneath is of a faint bluish-green colour in the 
two first-mentioned species ; in the last it is usually 
pure white, but sometimes tinged with blue-green. 
GENERIC DECOLORISATION, 
The fact that certain birds deposit white eggs 
in fully exposed situations has been pointed out 
as proof that the colouration could have no refer- 
ence to the exposure to light. But no notice has 
been taken, as far as I am aware, of the fact that 
all these instances occur in families where the 
majority of the species breed in holes or dark 
places. In this case decolorisation must have 
taken place at a much earlier period in the life- 
history of the family or genus than in the pre- 
ceding instances. They are probably descended 
from some ancestor which bred in holes; and the 
change to open nests in a few members of the 
family taking place long after the colouring 
matter had disappeared has not been followed by 
a restoration of the pigmentary covering. For 
proofs that pigment had at one time existed in 
these groups, we must look to the eggs of allied 
species. They occur in the Owls, the Pigeons, 
and the Petrels. 
“There is a strong and perfect similarity 
amongst the eggs of the different species of Owls,” 
writes Hewitson, ‘“ which we could scarcely ex- 
pect to find in the eggs of birds which differ so 
much from each other in their mode of breeding. 
The eggs of those species which are deposited in 
the hollows of old trees and deserted ruins, and 
those which are found on the bare sod, and ex- 
posed to the broad light of day and the pelting 
storm, are alike without colour.” But the large 
majority of the species breed in dark places, and, 
being nocturnal in their habits, all have a ten- 
dency to avoid light. Now their nearest con- 
geners, the Harriers, which link their family with 
the Falconide, bear a close resemblance to them 
in many points, e. g., the loose and flocculent 
character of the feathers, and the circular arrange- 
ment of those about the face; and the affinity on 
comparing the skeletons of each is most decided. 
In the colouration of the eggs also the resemblance 
exists, the eggs of the Harriers being white, or 
sometimes a pale skim-milk colour, more rarely 
spotted and smeared with brown. 
All the Columbidie, or Pigeon tribe, lay two 
pure white oval All, however, lay in 
crevices in rocks, hollow trees, deserted rabbit 
burrows, or dense thick trees or bushes. This, 
together with the fact that the nest of the arboreal 
members are crude platform-like structures, quite 
unlike those of any other bird, show that they are 
descended from an ancestor which bred in holes. 
One of the Australian Ground Pigeons is said to 
lay buff-coloured eggs. The nearest ally to this 
order, Pallas’ Sand Grouse, lays three oval eggs, 
similar to a Pigeon’s, but coloured like a Plover’s. 
vos 
eggs. 
