90 MOUNTAIN FAUNAS 
sharp bill to pick out its prey just as a butterfly uses 
its proboscis to suck up nectar. In the Alps another 
frequent bird is the rock-thrush (Monticola saxatilis), 
a brightly coloured bird, extending up into the barren 
regions of the mountain sides. In the Alps and Pyre- 
nees also the Alpine accentor (Accentor collaris) is 
common. With the exception of the hedge-sparrow, 
most of the accentors are mountain-haunting birds, 
having strong feet and legs, which fit them for pro- 
gression over rough ground. Of the summer visitors to 
the Alps, we may note the Alpine swift (JZicropus 
melba), which is larger than the common form. 
Reptiles do not appear to show any special adapta- 
tions to mountain life. It is remarkable that the 
common viviparous lizard (Lacerta vivipara) ascends 
to a height of 10,000 feet in the Alps, but then this 
hardy animal also extends into Siberia. The common 
viper (Pelias berus) also occurs in the Alps, though not at 
such a great elevation, and it has a similarly wide range. 
As regards amphibians, there is some evidence that 
the mountain habitat tends to produce darkening of 
the colour. Thus the common frog (Rana temporaria) 
occurs in the higher parts of the Alps in a dark-coloured 
variety, and the same thing is said to be true of the 
common toad (Bufo vulgaris). Similarly the Alpine 
salamander (Salamandra atra) is black in colour, and 
unspotted, thus differing markedly in colour from its 
allies. This form shows a peculiar adaptation to life 
at considerable elevations, in that it only produces two 
young at a time, and these pass through the gilled stage 
within the body of the mother, so that at birth they 
are lung-breathers like the parents, and not gill-bearing 
tadpoles. As the animal ascends to an elevation of 
9,000 feet, it is obvious that ice-free water for the 
