CONSPICUOUS COLOURS. 
229 
c «. 
ip. XVI. 
. 6 first year, and of tlie adults during the winter, are 
pure white, or much paler-coloured than during 
' e breeding-season. These latter cases offer another 
s t<ince of the capricious manner in which sexual se- 
ec -ti°n appears often to have acted . 61 
J he cause of aquatic birds having acquired a white 
lr Uage so much more frequently than terrestrial birds, 
h|°bably depends on their large size and strong powers 
flight, so that they can easily defend themselves or 
, s< a P e from birds of prey, to which moreover they are 
"l much exposed. Consequently sexual selection lias 
,lo t heve been interfered with or guided for the sake of 
h’otection. No doubt, with birds which roam over the 
"l H ‘ ri ocean, the males and females could find each 
I ler much more easily when made conspicuous either 
b being perfectly white, or intensely black; so that 
Ul 
<*du 
it discovers and flies down to a carcase floating 
the sea or cast up on the beach, will be seen from 
Steat distance, and will guide other birds of the same 
t A of distinct species, to the prey; but as this would 
® a disadvantage to the first finders, the individuals 
Oeh were the whitest or blackest would not thus have 
| oeured more food than the less strougly coloured 
• I^b'bduals. Hence conspicuous colours cannot have 
t en gradually acquired for this purpose through na- 
selection . 55 
( - se colours may possibly serve the same end as the 
notes of many land-birds. A white or black bird, 
Vo/ 0,1 Larus, Gavia, and Slerna, see Maogillivray, ‘ Hist. Brit. Birds, ’ 
bio 4 'do. 584, 626. On the Anser hyperboreus, Audubon, ‘ Ornifh. 
pLty ’’ vol> iv ' P' 562 - 0n the Anastomus, Mr. Blyth, in ‘Ibis,’ 
55 ’, P ' 
t) lf 6 lu ay be noticed that with vultures, which roam far and wide 
,tj jf u ob the higher regions of the atmosphere, like marine birds over 
0c ean, three or four species are almost wholly or largely white, and 
