126 



THE WORLD OF LIFE 



CHAP. 



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 . . 



2. Turdus musicus clarkei . . . 



3. Pratincola rubicola hibernaeus . 



4. Garrulus glandarius rufitergum . 



5. Loxia curvirostra scotica . . . 



6. Carduelis carduelis britannicus . 



7. Motacilla flava rayi .... 



8. alba lugubris . 



9. Parus major newtoni .... 

 i o. caeruleus obscurus . . . 



1 1 . ater britannicus . . . 



12. p'alustris dresseri . . . 



1 3. atricapillus kleinschmidti 



14. cristatus scotica . 



i 5. Aegithalus caudatus rosea . 



1 6. Regulus regulus anglorum . 



1 7. Sitta europaea britannica 



1 8. Certhia familiaris britannica 



1 9. Erithacus rubecula melophilus . 



20. Troglodytes troglodytes pirtensis 



21. Cinclus cinclus britannicus . 



22. Dendrocopus major anglicus 



23. minor comminutus. 



24. Lagopus lagopus scoticus . . 



British Bullfinch. 

 ,, Song-Thrush. 

 Stonechat. 



Jay- 

 Scottish Crossbill. 

 British Goldfinch. 

 Yellow Wagtail. 

 Pied Wagtail. 

 British Great Titmouse. 



Blue Titmouse. 



Coal Titmouse. 



Marsh Titmouse. 



Willow Titmouse. 

 Scottish Crested Titmouse. 

 British Long-tailed Titmouse. 



Goldcrest. 



Nuthatch. 



Tree-creeper. 



,, Robin. 

 St. Kilda Wren. 

 British Dipper. 



Great Spotted Wood- 

 pecker. 



,, Lesser Spotted Wood- 

 pecker. 

 Red 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 interesting 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 adaptations to the slight but undoubted 

 difference of climatal conditions which characterise our 

 islands. 



In confirmation of this view, a few cases have been 

 ecorded in which nature has been caught, as it were, at 



