1912] Miller: Pacific Coast Avian Palaeontology 



111 



Development of gigantic size in the cathartids is in effect 

 a case of over-specialization in that it works frequently to the 

 detriment of the species. The condors of today are of such 

 unwieldy size that, after a full meal, they experience much diffi- 

 culty in taking wing from low ground. This fact is reported 

 to have caused the destruction of many individuals which had 

 been led to alight in places from which they could not rise again 

 into the air. Teratornis must have attained a bulk almost thrice 

 that of the condor if we may judge from coracoid and furcula. 

 The suggestion conveyed by the sternum is that the pectoral 

 muscles were not so heavy in proportion, yet the weight of the 

 bird must have been far greater than that of the condors. The 

 nature of its food was such that it must have come to the ground 

 to feed. The effort to rise again, gorged with food, must have 

 been a severe tax upon its strength, and slowness in taking wing 

 may have subjected it to frequent danger. The high, compressed 

 beak of Teratornis resembling the eagle's in form, though struc- 

 turally cathartine, indicated the extreme of specialization. The 

 large body size, likewise a phase of specialization, may have mili- 

 tated in the end against the life of the species. 



The principle of specific decay or senility of species as a 

 cause of extinction may have suffered somewhat through the too 

 frequent application of it by the palaeontologist, yet there often 

 appear cases in which no other factor seems adequate to explain 

 the loss of a species. Certainly the intersterility of species would 

 lead to inbreeding with its attendant ill effects. Incipient strains 

 of intersterility within a species might, where geographically 

 restricted, lead to the more rapid deterioration of the stock ; 

 generation upon generation of individuals, like the succeeding 

 generations of somatic cells, become less and less virile until the 

 species would decline in a manner comparable to the senile decay 

 of the individual. The rapid decline of certain of the less con- 

 spicuous species of Hawaiian birds, such as Palmeria and Chae- 

 toptila, seems almost of necessity the result of such depleting 

 influence. How effective this factor was in robbing us of many 

 Pleistocene birds it is of course impossible to estimate ; it would 

 seem proper, however, to look upon it as possibly a contributing 

 cause. 



