BIRDS OF THE PAST IN NORTH AMERICA ^ 



By Alexander Wetmore 



[With 11 plates] 



When one considers that the number of forms of living birds 

 known at the present time is approximately 25,000, the fossil species 

 that have been discovered are remarkably few. The most recent 

 synopsis of the fossil birds of the world, that of Koloman Lam- 

 brecht, published in 1921, includes only 700 species, part of them of 

 doubtful identity. The list has been increased only slightly in the 

 seven years that have passed since this publication. At the present 

 date (October, 1928) there have been described 155 species known 

 only as fossils from that part of continental North America which 

 lies north of Mexico (but including the peninsula of Lower Cali- 

 fornia), this being the area covered by the American Ornithologists' 

 Union in its official Check-List. To complete the roster of fossil 

 forms for this region we must add 108 species now living whose bones 

 are found in deposits of Pleistocene age, so that the list includes at 

 the date just mentioned 263 names. The total is less than that for any 

 other group of vertebrates except the amphibia for this region. The 

 fossil reptiles, according to data supplied by Dr. O. P. Hay, now 

 include 1,011, or nearly four times the number of birds, while the 

 amphibians (without reference to supposed members of this group 

 named from tracks alone) reach a total of 156. 



That comparatively few students have taken up serious work on 

 our fossil birds may be due to three factors : First, the small numbers 

 in wdiich fossil bird bones ordinarily occur; second, the incomplete- 

 ness of the specimens in most cases ; and third, the lack in most mu- 

 seums of skeletal material of modern birds for comparative use. 



It is true that there have been occasional deposits in Pleistocene 

 beds in North America where bones of birds have been found in 

 great abundance, as at Fossil Lake in Oregon, and in the pitch de- 

 posits at Rancho La Brea in California, but these are exceptional both 

 in number of individuals and in range of species represented. Ordi- 



* Presidential address delivered before the Washington Academy of Sciences, Jan. 10, 

 1928. Reprinted, with change of title and some additions and changes, from the Journal 

 of the Washington Academy of Sciences, vol. 18, No. 6, Mar. 19, 1928, pp. 145-158. 



377 



