24 EDWARD A. WILSON. 
chick is a special development for its protection while lying on the snow-covered sea- 
ice which forms its earliest nursery, but this explanation is by no means borne out by 
facts. From September to December the chick exists on the floes of the sea-ice upon 
which it was hatched without ever entering the water. Its enemies, therefore, in the 
Antarctic can only be other birds. There are no seals that would disturb these chicks 
on the ice, and the only birds that might interfere with them are the Skua (Megalestris 
maccormicki) and the Giant Petrel ( Ossifraga gigantea). Both, however, are migrants 
and neither would appear on the Emperor Penguin’s breeding ground until the end of 
October, some two months after the chickens have left their eggs, and when they would 
already have reached the size of a full-grown Skua. 
I do not believe that the Skua is responsible for the death of any of the Emperors’ 
young, neither do I believe that the white down is the result of a need for protection 
from any enemies that we know as yet. 
The Giant Petrel might occasionally attack the young of the Emperor Penguin, 
but as far as our own and all other observations go, they lead one to look upon the 
Giant Petrel as a carrion-feeder with little tendency to attack living animals. It must 
also be remembered that, like the Skua, the Giant Petrel is far to the north at the 
outskirts of the pack ice in September and October when the Emperor chicks are in 
their most helpless state, and that they come southward only with the southward migra- 
tion of the Adélie Penguins in October. 
It may be said that the Sea Leopard (Stenorhinchus leptonyx) is a danger to the 
Emperor Penguin’s young, and this seal certainly feeds on full-grown Emperors, but these 
must be attacked and caught in the water, where the Sea Leopard is probably one of the 
fastest animals of the south. There is little reason to think that he would attempt to 
catch such an active animal as the Emperor chicken on an icefloe, where his own pace is 
slow and his movements clumsy, and where he may be seen sunning himself in friendly 
neighbourhood with other seals and penguins, none of which fear him on the ice.* 
It is obvious, therefore, that the white colouration of the Emperor chick has in 
this case nothing whatever to do with the theory of protective assimilation. The 
young bird while in the down is careful never to leave the ice, and there can be no 
reason to think that it requires any protection other than its parents can give it until 
it sheds the white down and takes on the dark grey plumage of the first year’s bird. 
This makes it still more difficult to supply a reason for its colouration. As a matter 
of fact, anything more conspicuous than a jet-black head, such as it has, on a field of 
smooth sea-ice could hardly be imagined ; but the ice of the pack is seldom smooth, and 
in a broken mass of disintegrating floes where every piece has others forced upon it, 
and the movement and wash of the sea has worn them into strange fantastic shapes 
with holes and hollows, it is easy to see that a white bird would be very inconspicuous 
indeed, and the more so if its whiteness is helped out by the addition of a black head 
* Dr. Pirie states, however, that the Sea Leopard has been seen to come up alongside a floe on which 
penguins were resting, seize one in its jaws, and sweep down again with its prey, Voy. ‘ Scotia,’ p. 222, 
