136 THE WOELD OF LIFE 



their continental allies. These include a distinct crossbill from 

 the highlands of Scotland, all our British titmice, which seem 

 to be especially modifiable, and several others. The complete 

 list is as follows : — 



1. Pyrrhula pyrrhula pileata British Bullfinch. 



2. Turdus musicus clarkei " Song-Thrush. 



3. Pratincola rubicola hibernaeus " Stonechat. 



4. Garrulus glandarius riifitergum .... " Jay. 



5. Loxia curvirostra scotica Scottish Crossbill. 



6. Carduelis carduelis britannicus British Goldfinch. 



7. Motacilla flava rayi Yellow Wagtail. 



8. " alba lugubris Pied Wagtail. 



9. Parus major newtoni British Great Titmouse. 



10. 

 11. 

 12. 

 13. 

 14. 



cieruleus obscurus " Blue Titmouse. 



ater britannicus " Coal Titmouse. 



palustris dresseri " Marsh Titmouse. 



atricapillus kleinschmidti . . . . " Willow Titmouse, 

 cristatus scotica Scottish Crested Titmouse. 



15. Aegithalus caudatus rosea British Long-tailed Titmouse. 



16. Regulus regulus anglorum " Goldcrest. 



17. Sitta europaea britannica " Nuthatch. 



18. Certhia familiaris britannica " Tree-creeper. 



19. Erithacus rubecula melophilus " Robin. 



20. Troglodytes troglodytes pirtensis , . St. Kilda Wren. 



21. Cinclus cinclus britannicus British Dipper. 



22. Dendrocopus major anglicus " Great Spotted Woodpecker 



23. " minor comminutus " Lesser Spotted Wood- 



pecker. 



24. Lagopus lagopus scoticus Bed Grouse. 



This last has been generally treated as a well-marked species, 

 but Dr. Hartert considers it, with all the others, to be a sub- 

 species — a species in the making. It is certainly a very inter- 

 esting fact that so many of our familiar birds are found to 

 present constant differences from their continental allies. 

 Most of these differences are of colour only, but some diversity 

 of bulk and in the size of the bill indicate the commencement 

 of structural modification; and these various differences from 

 the nearest continental species in so many of our resident birds 

 seem inexplicable on any other theory than that they are adap- 

 tations to the slight but undoubted difference of climatical con- 

 ditions which characterise our islands. 



