226 APPENDIX TO OSCINES. 



the Titlark, Green Blaek-ciipped Warl)ler, Lineoln's Finch, and Wiiite-crowned Spar- 

 row ; next, a Hiidsoiiiaii belt, extending from fiUO to 1,UU0 feet l>elo\\' the timber-liue, 

 iu which may be. found sub-alpine plants and such birds as the Canada Jay, Audubon's 

 Warbler, Brown Creeper, &c. ; then, of varying extent, a Canadian zone; below this, 

 an Allegiienian ; and, linally, on the plains, a Carolinian. It is quite impossible to fix 

 any prei-ise limits to these various fauuie, however; th(!y pass into each other (juite 

 gradually, and extend to such different elevations, according to the different inllueuces 

 to which they are exposed, that sometinuis two of them will be side by side for some 

 distance through the same altitudes, with merely a ridge intervening. 



Nevertheless, the temperature of a region, although it modifies the plant and insect 

 life to a great extent, determines entirely the range of birds. Jiinco liijonalii^ abounds 

 on the plains and up to 8,000 feet during winter, yet, in company with three of the 

 other four varieties that spend the winter iu the same localities, it migrates to the 

 north on the ajjproach of the breeding season, while •/. eauiccps alone ascends the 

 niouutains, and tiuds the requisite clinuite in the higher forests, whicli the others seek 

 at higher latitudes. Yet it is well known that the Snow-bird breeds in the Alleghauies 

 further south than this region; and there appears no obvious reason for a northern 

 migration, when it could easily find any desired temperature by ascending the mount- 

 ains in compauy with its cougener, J. caniceps. Ou arriving from the north, most 

 birds apftear among the foot-hills and along the edge of the plains, some days in ad- 

 vance of their arrival higher up iu the mountains; and the same thing occurs during 

 the vernal miiirations, showing that most of the species prefer uiigrating along the 

 edge of the plains rather than through the mountains. Even so northern a species as 

 Anipelis (jarndiis, Vtdiich, during midwinter, is rare among the foot-hills, frequently 

 gathers there in large flocks, iu spring, preparatory to its leaving the country. The 

 boundary between plains and mountains appears to be a highway for all the migratory 

 species in spring and autumn. 



The most prominent characteristic of the avi-fauna of this region — which may be 

 taken as a fair type of the Rocky Mountain chain between the thirty-eighth and forty- 

 Urst parallels — is, perhaps, the remarkable number of birds which are represented 

 further east by very closely-allied races or species. Of these there are over twenty ; 

 and Avhile some are plainly varieties shading into the eastern forms by such imper- 

 ceptible gradations as to leave no doubt of their specific identity, others cannot be so 

 summarily disposed of. No one has shown, for iustauce, that 4h'othliipi:i inacr/iUivraj/i 

 is connected by gradual, intermediate stages, with G. philaddphia ; or that Jitnco caiti- 

 ccps is similarly related to the other forms of its genus. But iini we to acc^ept this 

 detinition of a species? Are only such fonns eutitled to specific rank which cannot 

 •be shown to intergrade with others? The teudeucy of the day is decidedly in that 

 direction; yet, if logically carried out, this system will eventually lead to startling 

 results. If PipiJo erjithrophthalmuH can be showu to gradually pass into P. arcticns to- 

 v.ard the Eocky Mountains, and into P. allrni in Floiida; and if the former changes 

 into orcijoiiHa and mi'duloujix ou the Pacific coast, anil thus all these forms are to consti- 

 tute a single species, what reason is there for still keeping apart the various races of 

 Colaplt's, which intergra(h) quite as clo.selyf Carpodacus vasbini is considered a good 

 species; yet its points of diiierence irom C. pinpiirens are fewer and less marked than 

 those separating Contopits virciis and C. rwhardaouii, which are now thiowu together 

 uuder the same specific name. New links and new intermediate forms are constantly 

 coming to light ; and if, on discovering the gradation between any two forms previ- 

 ously held as good species, we are at liberty to combine them as races of the same 

 species, will it not be equally proper to combine other forms togfcther, even though 

 some of the intervening links are wanting, where analogy and experience point to that 

 conclusion? It is the exact reverse of Biehm's system, which letl that ornithologist to 

 find no end of species, where others could see but one. 



The results of this system of reasoning are already beginning to manifest themselves. 

 Different forms are thrown together with the utmost freedom, and we are learnedly 

 referred to " well-known laws'" of geographic and climatic variation. Yet there are 

 cases where these "laws" will not work at all, and then thtiy are (]uietly ignored. In 

 the Rocky Mountains, for example, a species of Wren is found, so well marked iu its 

 notes, plumage, and habits, that tlie old;;r ornithologists considered it ipiite distinct; 

 but being somewhat like the eastern House Wreu, only grayer and paler, it is at once 

 referred to that species, and its changed color accounted for by the "law" that, in this 

 region, the dry air and bright sunlight exercise a bleaching inilueuee. In the same 

 locality, and existing uuder precisely siuiilar physical conditions, is a species of Fiy- 

 catcluu', also supi)osed by Audubon and the okler school to be a distinct species, but 

 whicU these modern ornithologists |)rouounee to be " var." richardsoiii of the eastern 

 Wood Pewee. Unfortunately, in this case, the bird happens to be darker than its east- 

 ern rehitive, and so we have not a word concerning the "laws of clinuitic variation" 

 and the " mean amount of rain-fall." Nor do the chief exponents of this new method 

 of reasoning tind any limits to their course when once fairly started. In a review of 

 a certain genus of the Tyrannidcv {Myiarvhuti), one of our j)reseut writers has declared 



