38 



Iowa Orxithologist. 



would scarcely be safe to say that there was any close genetic relationship 

 between tlieni. 



Basilenterus and Eiithlypis seem to point back to the Setophaga type with 

 Flycatcher affinities, though in plumage they resemble the more highly 

 specialized genera. 



This completes the list of genera and probably all the near alliances have 

 been touched upon, though of course it cannot be claimed that each has been 

 given its due prominence. 



Perhaps no other well-defined family of birds shows more varied and intri- 

 cate relationships ; they embrace a considerable niimber of widely separated 

 familie.s in both sub-orders of the Passeres. 



Let us now turn for a moment to the geograpliical distribution of the group 

 and afterwards draw our conclusions as to its probable origin and past history. 



The absolute range of the Warblers extends from the arctic region to Chili 

 and Bolivia, but comparatively few species cross the equator. Now, leaving 

 out of account the annual migrations of the northern species and considering 

 the breeding range as the true habitat, the whole territory of the family may 

 be divided into two well-defined regions. The boundary line between these 

 regions extends from the coast of Texas about one hundred miles north of the 

 southern boundary, through southern New Mexico and Arizona, reaching the 

 Pacific Ocean at the southern extremity of California. It will be seen that this 

 line is at least a thousand miles north of the southern point of the Nearctic 

 Rgion as defined by Wallace in his "Geographical Distribution of Animals." 

 Not only the species, but also the genera are almost wholly different in these 

 two regions. This will be clearly shown by the following tables, the genera 

 w itli the number of species characteristic of each region being given with the 

 number of species found in the otlier. 



NORTHERN REGION. SOUTHERN REGION. 





■ 2 



5 t" 



■2 f 1 





. »• 



S tc 





° Oc 



Genera. 



^'1 



o 1 



■2 "o J 

 Ifl 



Si* 



» g -S 



Iff 



Genera. 



* 1 







§ o 



Mniotilta 

 Protonotaria 



1 

 1 



1 

 1 







Oreothlypis 



Compsothlypis 



Geothlypis 



3 



G 



11 



3 



5 



7 





1 



4 



Helinaia 



1 



1 







Teretistris 



3 



3 







Helminthophila 



8 



7 



1 





GJranatellus 



4 



4 







Dendroica 

 Seiurus 



m 



4 



31 



2 



13 



1 



Setophaga 

 Carclellina 

 Ergaticus 



15 

 1 

 3 



14 

 1 

 3 





1 



Icteria 



1 



1 







Basileulerus 



33 



33 







Sylvania 



f) 



8 





3 



Euthlypis 



1 



1 







Total 



oT 



88 



:j 



16 



Total 



66 



60 





6 



These figures are very interesting and significant. In the first place, they 

 show a well marked geographical division of the family into two nearly equal 

 parts or sets of genera. Further, it will be noticed that the four most highly 

 specialized genera, Protonotaria, Helinaia, Helminthophila and Dendroica, are 

 characteristic of the northern region, though thirteen of the thirty-six in the 

 last are confined to the southern. Oreothlypis and Compsothlypis, the most 



