THE GIANT PETREL. 99 
My object is to point out that there must be some active reason for the pre- 
ponderance of this pure white phase within the limits of the ice. Yet it is not 
easy to see how the facts can be brought within the range of the ordinary theories 
of animal colouration. 
In the first place, it is fairly certain that the Giant Petrel has no need for 
protective assimilation to its surroundings in the ice, and yet this is possibly the first 
idea that occurs to one on learning that a white variety of a dark bird is very much 
more abundant within the Antarctic Circle than without. But it is quickly followed 
by a question respecting the enemies it hopes thereby to escape, and in this particular 
case the answer disposes at once of the protective assimilation theory, because the 
bird, whether black or white, has no enemies that are worthy of the name. In 
the water, no doubt, it might be surprised by a Killer Whale (Orca gladiator) 
or a Leopard Seal (Stenorhinchus leptonyx), but the position of any bird which 
can rapidly take wing from the surface of the water and never goes below is 
obviously not such as would require invisibility to protect it from such enemies as 
these. 
Both beasts give ample warning of their approach by the noisy way in which 
they breathe. They are dangerous only to such birds and beasts as live habitually 
below the surface, where their approach is as sudden as it is silent and unannounced, and 
where little safety is to be found in anything but superior speed and more rapid 
powers of turning. On the ice floes the Giant Petrel, no matter what may be its 
colour, shows by its lack of nervous apprehension that it is not as a rule concerned 
with anything that may be there, except it be in the nature of something it can eat. 
We may, therefore, quite safely dispose of the assimilation theory so far as the protection 
of the bird from its enemies is concerned, and equally safely, I think, in so far as it is 
supposed to help the bird in obtaining food. 
The Giant Petrel lives on any carrion that it is able to discover, and it can never 
be at a loss during the Antarctic summer for a plentiful supply of dead seals and 
penguins. I know not whether in the Macquarie and Auckland Islands and elsewhere 
it is also mainly a carrion feeder, but I can answer for this in the Antarctic. One has 
but to kill a seal on the shore in summer and visit the blubber refuse day by day 
to realise how quickly such food attracts the birds who are looking for it. None but 
the carrion feeders come to it; one sees no Albatross, no Snow, Antarctic, or Wilson’s 
Petrel, though all must often scent it; but the Giant Petrel and the Skuas come in 
constantly increasing numbers. 
It is a fine sight to watch a Giant Petrel, with a stretch of wing as extensive 
as that of an Albatross, beating up the wind in large circles along the shore in search 
of scraps that the tide has left there. His flight is as even as the flight of a Diomedea ; 
for long one may watch in vain to see a stroke of the wings, but without an effort he 
now rises against the wind till almost at a standstill, and now with a wide majestic 
sweep turns out to sea, and so once more up into the wind again. It is a labour- 
