88 



THE WORLD OF LIFE 



CHAP. 



driven to us by storms, and have only perhaps been recorded 

 (seen or killed) once or twice. There is therefore a vast range 

 for personal opinion as to what species should or should not 

 be included as " British " or " European " or " Canadian " 

 birds. If we add to this uncertainty the extreme variety 

 of opinion as to the limits of " species," " sub-species," and 

 " varieties," or " local races " of birds which now exist, we 

 see how hopeless it is to expect uniformity in numerical 

 estimates of the birds of different countries or regions. As 

 an example of this difference of treatment, we may take two 

 of the most recent estimates of the bird-population of the 

 world. Dr. Gunther, in 1 8 8 1 , estimated the species of birds 

 then known at 11,000, and Mr. Shipley added to this an 

 average of 105 new species per annum estimated from the 

 Zoological Record for the twenty-seven years elapsed since 

 that date, bringing the total up to 13,835. But in the late 

 Dr. Bowdler Sharpe's Hand List of the Genera and Species 

 of Birds, just completed, the number is stated as being 

 1 8,937- This enormous divergence, as I am informed by 

 another great authority on Ornithology, Dr. P. L. Sclater, is 

 mainly, if not wholly, due to the fact, that Dr. Sharpe 

 " includes as species all the numerous slight local forms which 

 are called ' sub-species ' by the new school of Ornithologists, 

 many of which, in my opinion, do not present sufficient 

 differences to require separation at all." 



Keeping these difficulties in mind, the following estimates, 

 for which I am largely indebted to my friend Mr. Henry 

 Dresser (author of a great work on the Birds of Europe), will 

 be found interesting : 



SPECIES OF BIRDS 



1 Mansel Pleydell's Birds of Dorset. 



