228 U. S. NATIONAL MUSEUM BULLETIN 217 



four or five positions he returned to a point near the first perch. The 

 Bong and singing positions were conspicuous but the thickness of the 

 brushy surroundings and the brevity of the bird's appearances made 

 it difficult to observe them near the ground. 



After several males had been collected, a special effort was made 

 to find females and evidence of nesting. The sexes could not be dis- 

 tinguished in appearance and apparently were not distinctive in action 

 in their wet marshy terrain under the thick willows, for only three 

 females were obtained. One of these, taken on June 7, had an egg 

 ready to lay and one taken on June 12 contained a formed egg and a 

 collapsed ovarian follicle. 



The Indians know these birds as Chootzi. 



After examining our waterthrushes at the IT. S. National Museum, 

 Herbert Friedmann wrote me, "McCabe and MiUer (1933) indicate 

 that JS. n. notahilis exists in two geographically separate populations. 

 These birds [from Old Crow], from the northwestern of the two 

 groups, are darker above, varying in the direction of limnaetis, from 

 which race some of the individuals are difficult to separate. This 

 raises the possibility that the western section of notdbilis may better 

 be grouped with limnaeits, and in this way we can do away with the 

 discontinuity in the distribution of notahilis which McCabe and Miller 

 indicated." 



The migratory course of these waterthrushes does not appear defin- 

 able from the scattered records of localities. Since they approach the 

 western race in appearance it may be presumed that their migration 

 passes west of the Mississippi. 



Wilsonia pusilla pusilla (Wilson) 



Males Females 





Weight 



Fat 



Testes 



Weight 



Fat 



Eggs 



Bate 



(ff.) 





(mm.) 



(g.) 







May 20 



8.6 



NF 



4x7, 4x4.5 









May 21 



7.7 



LF 



3.6x5, 3.5x4 









May 22 









7.3 



VLF 



0. 75 mm. 



May 29 



7.9 



NF 



3x4, 









Junel 



7.6 

 7.3 



7.7 



VLF 

 VLF 

 LF 



6x7, 4.5x5 

 4x6.5, 6x6 









June? 









8.8 



LF 



4 broken follicles, 

 1 formed egg, 

 brood patch 



Junes 



7.6 



NF 



6.5x8.5, 5x6.5 



8.1 



LF 



2 mm. 



June 10 



8.3 

 7.3 



LF 

 LF 



6x8, 5x6 

 4.6x6, 6x6 









(Aver.) 



7.8 (Coefl. of 



var. 6.2%.) 









The first Wilson's warblers seen were singing in low willow brush, 

 where they were subsequently often seen, usually near running water. 

 The first part of their Indian name, Tsetso khekui, means water. 



