TYRANNIDJE—TYRAXNIN.E: TYRANT FLYCATCHERS. 527 



Tlie bill varies with the species in size and shape, from almost as broad and flat as in a Wood 

 Pewee in E. rirescens (formerly called acadicus) to the narrower shape of a Pewit in E. wrighti; 

 but it is always much shorter than tarsus. The sexes are alike in this genus, as usual in 

 the family; the young similar, usually rather more yellowish or buffy. The nest is placed 

 in trees or bushes ; the eggs are white, spotted or not in different species, thus affording good 

 clews in some cases of doubt. It sht)uld not be difficult to recognize Empidonax as different 

 from Contopus, due attention being given to the nice points of diagnosis; but it is not easy to 

 discriminate the numerous species without much tact, care, and patience. The following ac- 

 count, carefully prepared after examination of a great amount of material from all parts of the 

 country, will probably suffice to determine nearly all specimens. How much alike are these 

 interesting little birds may be inferred from the fact that Wilson in 1810 knew but a single 

 species, virescens, which he called museicapa querula, to which Audubon added but one, which 

 he named traillii, in 1832, until Baird in 1843 showed him two more, minimus Rxxd Jlaviventris. 

 Yet these four are perfectly distinct birds. Any experienced collector knows these four to be dif- 

 ferent, not only when he has them in hand, but in life, by their haunts and habits, their notes, 

 nests, and eggs — indeed, the nests and eggs of each of them are readily discriminated. Three 

 of them occur in New England as breeders — traiUi alnorum, minimus, and flavirenfris ; while 

 rirescens is the common breeder in the Middle States. The case is complicated, however, in the 

 West. Since 1858, when Baird first fixed our species upon anything like a satisfactory footing, 

 few changes of his determinations and characterizations have been established ; but several 

 species which were unknt)wn to him have been added to our Fauna, and some changes of 

 nomenclature have been introduced (see especially the cases of the so-called " Acadian" and of 

 eastern and western "Traill's" Flycatchers, as treated by Brewster, Auk, Apr. 1895, pp. 157- 

 Hj3). It is not reasonably possible to analyze all the forms in concise phrase ; the student 

 must go at once to the detailed descriptions ; but the following may help him somewhat : 



A. Species clearly olivaceous of some shade above : below ivhiiish more or less shaded on breast, or clearly yellouish, 



but adults never buffy. (Empidonax proper ) 

 Eastern. 



Largest : rather over than under 6.00 ; wing nearly or over 3.00 ; tarsus 0.67 ; middle toe and claw 0.50 ; bill 



nearly or quite 0.50. Clear light o\\\&-green above, below whitish ; wing-bars and eye-ring tawny. Nest fiat 



in fork of a horizontal bough ; eggs speckled. Hardly N. to New England. Virescens (formerly called acadicus) 

 Medium : rather under 6.00 ; wing 2.70 ; tarsus 0.C7, but middle toe and claw 0.60 ; bill hardly 0.50. Olive- 



broun above, below grajush ; wing-bars and eye-ring whitish. Nest a bulky cup in a bush; eggs speckled. 



New England, etc trailli alnorum 



Small : rather under 5.,50 ; proportions and colors nearly as in trailli. Nest a neat cup in upright crotch of a 



tree; eggs white. Commonest breeder in S. New England, etc minimus 



Medium: under parts thoroughly yellow. Nest near ground in a stump, moss, etc., bulky. Eggs speckled. 



Northern New England, etc fiaviientris 



Western. 



The stock-form of traiUi alnorum as above described. Eggs speckled. Mississippi valley and westward 



trailli (formerly called pusillus) 

 The representative of flarirentris in the west. Thoroughly yellow-bellied. Eggs speckled .... difficilis 



The representative of difficilis in Lower California. \ot thoroughly yellow-bellied cineritius 



Tlie representative of difficilis. Santa Barbara Isls insulicola 



Small, and otherwise like minimus; dark below, breast not very different from back ; bill extremely narrow. 



Eggs white. Western N. Am. at large hammondi 



Large, about the size of acadicus ; olive-brown above ; breast dark ; outer tail-feather white on outer web ; bill 



very narrow. Y.ggs while. Western U. S wrighti (iormtrXy caiXeA obscurus) 



Tlie representative of wrighti in Lower California. Larger, grayer, etc gri-seus 



B. Species more or less decidedly buffy. Exclusively southwestern. (Section Mitrbphanes. ) fulvi/rons and /. pygmiTus 



Another analysis may be made which will suit some students, as follows: — 



A. Empidonax proper ; no buff-bellied species. 

 Belly decidedly yellow. 



Eastern flavivenlris 



Western difficilis 



Lower California cineritius 



