The California Linnet 



plished this adjustment by virtue of its inherent and special adaptability 

 (however derived). This phenomenal adaptability, or tolerance of change, 

 still remains the most prominent inheritance, or characteristic, of the 

 species, and has made it the dominant form of the region which it occupies. 

 This adaptability owns only one restriction, albeit an important one. The 

 House Finch is closely dependent upon water, and is rarely found breeding 

 at a distance above half a mile ("a few hundred yards," Dr. A. K. Fisher 

 says 1 ) from stream or spring. But again, adaptability, or ease of accom- 

 modation to environment, is not to be confused with plasticity, which is, 

 rather, susceptibility to change in environment, and which reflects itself 

 in the altered structure or appearance of the bird. Of this latter charac- 

 teristic the Song Sparrow, Melospiza melodia, with its twenty subspecies 

 in California alone, is a most conspicuous example. The House Finch, on 

 the other hand, overrides obstacles, and is able to absorb, as it were, the 

 shocks of change within its corporate, or specific, body, without evidence 

 of corresponding somatic change. 



One of the results of this ability is a certain tendency to vary, which 

 exhibits itself in off-plumages and freaks, quite independently of associa- 

 tion or environment. Thus, it is well known that partial albinism is 

 common among House Finches. Among adult males, also, a more or less 

 complete substitution of yellow for red is sometimes encountered. Caged 

 birds are certain to lose their rosy tints, and to put on this mongrel yel- 

 low. That this tendency to dichromatic manifestation is more evident 

 in insular examples is probable; and it may be that insular conditions, 

 like confinement, for some reason fail to support the production of red 

 pigment. As a further example of freakishness, Swarth cites a case 

 where two young females, caught in the wild, showed distinct traces of red 

 in their plumage. 



This trait in the House Finch, which we have rather carelessly called 

 the tendency to vary, may either be due to the species having reached the 

 saturation point of numbers, or the limit of vitality in development. Con- 

 ceivably these freakish manifestations may be evidences of phylogenetic 

 weakness, or approaching decay, rather than promises of new departures 

 in development. On the whole, I think the evidence of the eggs rather 

 supports the latter view. The type is weakening. Whereas the egg is 

 normally pale bluish green with blackish markings, sparingly applied, 

 white shells are not rare, and some sets are entirely devoid of markings. 

 Runts and other freak eggs are relatively numerous in this species, also. 



But without pausing longer to establish the geno-dynamic status of 

 the species, we hasten to note that in its nesting habits the California 

 Linnet exhibits the utmost diversity of taste and the utmost degree of 



1 Report Death Valley Expedition (1893), p. 80. 



2IQ 



