Virginia and hicim are restricted in their ranges, being char- 

 acteristic of the Colorado Valley and Southern Rocky Mountain 

 region. 



The other section comprises bachmani, chrysoftera, fmus, 

 and their curious allies, laivrencei and leucohronchialis ; birds of 

 striking coloration and of much more restricted ranges than the 

 three plainer colored species of the former sub-group. Bachmam 

 is exceedingly rare, having been taken but a few times in the 

 Southern States. The Blue Golden-winged Warbler, chry- 

 softera, and the Blue-winged Yellow Warbler, finus, are 

 exclusively birds of the Eastern Province, the former rangmg 

 into Canada, though rarer in the Northern States, the latter 

 scarcely if ever going beyond Massachusetts and Minnesota. 

 Both winter south of our limits. 



I have taken the liberty of thus hastily reviewing the genus for 

 the purpose of bringing together as nearly as possible our present 

 knowledge of the distribution of the several species. The history 

 of the two forms laivrencei and leucohronchialis is already so 

 well known to ornithologists that it need not be reiterated here, 

 except to recall the very general belief of their hybrid nature. 



The question naturally arises in the minds of most persons 

 who have given any thought to the subject. What does the oc- 

 currence of such peculiar forms, taken in conjunction with other 

 facts, signify.? We are stepping into a somewhat uncertain re- 

 .gion when we attempt to speculate on a subject of this character, 

 ' but I believe that the only way in which we may hope to throw 

 any light whatever upon such a subject is from an evolutionary 

 standpoint. 



The rise and decay of genera and species in the struggle for 

 existence ; the pressure of dominant groups upon smaller and 

 less adapted races ; action and reaction through environment ;— 

 these are the factors involved, and that have given rise to many 

 apparently inexplicable phenomena. 



A dominant group is characterized by the abundance of its 

 forms, both in species and individuals, over wide areas, this being 

 the index of its vigor and consequent ability to maintain itself 

 against competitors, and its adaptability to varying conditions of 

 environment. Rarity in species and individuals is indicative of 

 degeneracy, the expression of the inability of the group to hold 

 its own. 



Hybridism under nature is a further expression of decay, the 

 result of a growing rarity in the individuals of a species. 



Of course a hybrid may be purely accidental, as I believe the 

 case to have been with the cross between the Barn and the Cliff 

 Swallow which I described some years ago, the result of a mesal- 

 liance between two individuals during the spring flights when 

 numbers of both species are 'hawking' in the air together prior 

 to nesting. But when we see crossing repeatedly performed the 

 question of accident must be set aside and another means of solu- 

 tion sought. 



Let us see how these principles will apply to the genus Hel- 

 minthophila. Here we have a group of eight species, as has 

 been cited above, none of which are as a rule very abundant, 

 especially when compared with other birds, e. g., certain species 

 of Dendroica. 



Recalling the distribution of the species, we find that each has 

 a more or less definite area, but their habitats considerably over- 

 lap one another That of the two sub-divisions noted, celata^ 

 rujicapilla, and feregrina are the most widely distributed, while 

 chrysoptera, pinus, and their allies are much more restricted, and 

 it is in this latter section that we find what is to my mind an evidence 

 of decay. Strictly insectivorous, the Heltninthophilce have come 

 in direct competition with other insectivorous forms, and among 

 them the closely allied and dominant genus Dendroica, with its 

 thirty odd well defined species, whose habits and nature closely 

 resemble the Swamp Warblers in many ways. The pressure ex- 

 erted by Dendroica would be very much greater in the East than 

 in the West, owing to the greater preponderance of individuals 

 and species in the former area ; consequently the more restricted 

 eastern species of Helminthophila would feel this competition 

 keenly. 



Many of the Dendroica pursue and capture their food in much 

 the same manner as the HelminthophilcE, and in similar locali- 

 ties ; more than this, the majority are expert fly-catchers, taking 

 mature insects on the wing with much greater readiness and per- 

 sistency than do the species of Swamp Warblers. A glance at 

 the bills of the two will show which is the best adapted for diver- 

 sified work. 



And what has been the upshot of all this.? Simply that these 

 restricted species of Helminthophila are succumbing to more 

 wide-spread and better adapted forms, and their decrease in num- 



