76 



The Canadian Field-Naturalist. 



Vol. XXXV. 



SWARTH ON THE FOX SPARROW. 

 By p. a. Taverner. 



Tliis jnonograph on the Fox Sparrows is 

 an excellent example of the species-splitter 

 at his best, and worst. That sixteen sub- 

 species are recognized is testimony to the 

 fineness of the splitting, but the use made 

 of these fragments goes a long way to 

 justify the process. Too often systematists 

 have assumed, when they have divided their 

 species into as many fractional parts as 

 possible, that their responsibility was end- 

 ed, whereas they have only just laid out 

 their tools for serious scientific effort. Mr. 

 Swarth realizes that splitting is a means to 

 an end and not an end in itself, and has 

 developed his subject with a grasp and ap- 

 preciation of the problems involved that 

 is all too rare in revisions of this kind. 



The first 29 pages are taken up by an 

 introduction and chapters on Materials 

 and Methods of Treatment, History, Varia- 

 tion in Passer ella iliaca and Distribution 

 and Migration that are models of their 

 kinds. The remainder is composed of 

 systematic treatment, description and dis- 

 cussion of the races considered, a list of all 

 the material examined and a beautifully 

 drawn and colored plate from the brush of 

 (mr countryman Major Allan Brooks illus- 

 trating the extremes of two subspecific 

 groups. 



The species is remarkably homogeneous 

 over most of the continent but breaks \\\> 

 into many races within and west of the 

 Rocky Mountains. These races are dis- 

 cussed, their relationships pointed out. 

 they are traced from their summer to their 

 winter habitat, and many interesting prob- 

 lems regarding them are suggested. 



An interesting conclusion is derived 

 fr(^m the movements and distribution of the 

 British (^olumbia and Alaska coastal forms. 

 Those that summer farthest north winter 

 the farthest south. The more southern 

 breeders winter more northerly, and so on 

 progressiveh' to the Vancouver Island 

 vicinit}' birds which are practically station- 

 ary throughout the year. 



Another important point brought out is 

 that the birds breeding in the most humid 

 climates are not the darkest or the largest 

 of the species. Unalaschensis, summering 

 in the extremely moist Alaskan Peninsula, 



does not reach the extreme development of 

 size or depth of color that is attained by 

 fuliginosa, resident on the comparativeh' 

 dry Vancouver Island region. This per- 

 plexing fact that would otherwise serious- 

 ly shake one of our most cherished ecolo- 

 gical principles is explained by the fact 

 that t;ie northern race spends its winter 

 in arid southern California, and probably 

 experiences a much lower annual average 

 moisture than does the darker and larger 

 race. It is thus brought forcibly to oui- 

 notice that, in studying the relationship 

 between the bird and its environment, 

 winter ranges and probably migrational 

 routes should also be taken into considera- 

 tion. 



Some distributional anomalies are point- 

 ed out. Some forms range widely over 

 varied and more or less discontinuous con- 

 ditions unmodified, w^hilst very slight bar- 

 riers have induced specialization in others. 

 Kadiak Island, but slightly isolated from 

 adjoining territory, has its definable sub- 

 species, insularis, yet the Queen Charlot- 

 tes, situated far out to sea and noted for 

 their peculiar forms, have developed no 

 specialization in this species. 



Mr. Swarth divides the Fox Sparrow, 

 Fasserella iliaca, into sixteen subspecies 

 falling into three groups which for con- 

 venience he calls after their most char- 

 acteristic com])onent members. Thus he 



gives us :- 



1. 



9 



1. F. 



2. P. 



3. P. 



-The Iliaca grouj). 



P. i. iliaca 



P. i. altavagans 



II. The Unalaschensis group. 



/. vnalaschensis 4. P. i. annectens 

 i. insularis 5. P. i. town send! 



i. sinuosa 6. P. i. fnliginosa 



III. The Schistacea group. 



1. P. 



2. P. 



3. P 

 3. P. 



Of 

 as br 

 first 



schistacea 

 fulva 



megarhynchus 

 hrevicauda 



5. P. i: 



6. P. i. 



7. P. i. 



8. P. i. 



canascens 

 monolensis 

 mariposae 

 stephensi 



these we have nine in Canada either 

 eeders or migrants, including all the 

 two groups and the first of the third. 



