ST.-KILDA WREN. 663 



in both hemispheres is soon subjected to the influences of many disconti- 

 nuous areas of distribution. Each isolated area becomes the centre of a 

 new race, which can only interbreed within itself and thus soon becomes 

 slightly differentiated. Thus the Wrens of Iceland, St. Kilda, the Faroes, 

 Behring Island, the Kurile Islands, Japan, North China, and Nepal have 

 developed large feet, probably in consequence of living more on rocks than 

 trees. Those of Nepal, North China, and Japan have become very dark 

 in colour, a heavy rainfall accompanied by heat being apparently favourable 

 to deep colour ; whilst those of Algeria, Turkestan, and Cashmere, where 

 the rainfall is exceptionally small, but the sun very hot, are remarkably 

 pale. A very similar effect seems to have been produced in St. Kilda and 

 Behring Island by exactly opposite causes, namely, plenty of rain but very 

 little sun. Why the Wrens of Central Europe, England, and the Pacific 

 coasts of North America should differ from the other races in having no 

 dark bars on the back it is difficidt to surmise ; but neither with regard to 

 this character, nor to any other which has been mentioned, can a hard- 

 and-fast line be drawn. 



The St. -Kilda Wren has been obliged by force of circumstances to change 

 its habits as well as the colour of its dress. It would be interesting to 

 know how many thousand years ago the accident happened which gave 

 St. Kilda a Wren. Doubtless some flock of Norwegian birds migrating 

 southwards to find a milder Avinter in Great Britain were driven out of 

 their course and took refuge on the lonely x\tlantic island, where their 

 descendants, modified by time and circumstances, still survive. 



Of the habits of this bird Dixon writes : — " The most interesting residt 

 of my trip to St. Kilda last year was the determination of its Wren, called 

 ' Dhra-in-doun ' by the natives. Although this little Wren was known 

 to Martin nearly two hundred years ago, neither he nor any subsequent 

 naturalist had the least idea that the bird was different from the Wren 

 inhabiting the rest of the United Kingdom. It is very interesting to find 

 such a delicate little bird isolated so far from the mainland, and frequent- 

 ing such a wild rock-bound haunt ; and its cheery song enlivens the bare 

 hill-sides, even the gigantic precipices where the Fulmars rear their young. 

 Viewed from the sea, St. Kilda looks far more barren and dreary than it 

 really is. Not a tree or a shrub relieves the monotony of the bare hill- 

 sides or even the sheltered valleys; but grass grows luxuriantly, makino- it 

 literally an ' emerald isle,^ and primroses, sorrel, and many other plants 

 thrive on the cliffs and sloping banks. The hill-sides, even to the summit 

 of Connacher, 1200 feet above the sea, are thickly studded with rough 

 hovels, or ' cleats,^ made of boulders and roofed with turf, in which the 

 St.-Kildans dry their ' turfs ' and grass, and where the sheep take refuge 

 during bad weather. I had not been on St. -Kilda long before this Httle 

 bird arrested my attention, as it flew from rock to rock, or glided with 



