1912] Miller: Pacific Coast Avian Palacontology 111 
Development of gigantie 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- 
eulty in taking wing from low ground. This facet 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 fureula. 
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 strue- 
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 specifie 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. 
