110 BIRDS OF ILLINOIS. 



still further; for not only are the giMieral hnbits nearly identical, 

 but the appearance of the eggs, Btructure and situation of the nest, 

 and general characteristics of song are quite the same. These te- 

 leological resemhlanccs, ho'.vc-ver, are no indication of relationship; 

 on the other hand, the two families are (juite far removed from one 

 another in the great assemblage of Passerine birds. It is unneces- 

 sary to allude to the differences here, since they have been suf- 

 ficiently elucidated on page 48. 



The two North American species of this genus which may be 

 properly mentioned in the present connection differ as follows : 



n' First and fourth primnrios dooidedly or appreci.ibly shorter than ern'ond and third; 

 hind toe (with claw) shorter than tarsus; outstretched feet falllni; considerablf 

 short of end of tall. Lateral tail-feathers with Inner webs partly dusky. (Antliui)). 



1. A. pensilvanicus. Legs and foot always deep brown or dusky. In summer, above 



nearly uniform grayish brown; beneath deep pinkish bulT, the jueulum moro or 

 less streaked with dusky irarely nearly immaculate). In winter, above olive- 

 brown, the pileuni and back Indistinctly streaked with darker; beneatli ochreous- 

 bufl. the jnculum broadly streaked with dusky. Wing about 3.15-3.3ii, lall2.40-2.G0. 

 culmen .■l2-..';o, tarsus .SO-.W). 

 a- First primary as long as or longer than second; hind toe (with claw) longer than tar- 

 sus; outstretched feet reaching nearly or Quite to end of tall. Lateral tail-feathers 

 with Inner webs wholly while (for e.\posed portion). (.Vro<on/.«.) 



2. A. sprajueii. Bill, leg^. and feet pale-colored, themaxilla. only, dusky. In summrr, 



above broadly streaked with light bufT-grayish and brownish dusky; lower parts 

 dull biilTy white, more strongly tinged with bulT across juguliim, where narrowly 

 streaked with dusky. In irinlrr, beneath much deeper buIT. the jugular streaks 

 broader; upper parts with the pale streaks more decidedly buff. I'mmj. with 

 upper parts moro broadly streaked with blackish, the feathers, especially on 

 back, bordered terminally with white. Wing, about 3.20-3.40; tail, 2.35-2.60; cul- 

 men, .45; tarsus, .90. 



The A. spragueii has usually been placed in a so-called genus 

 Neocor;/s, Sclater ; but the variations in the details of external form 

 are so numerous among the many species of the genus Authm, in 

 its comprehensive sense, that the recognition of generic value in 

 the differences which exist between .1. pciifiilriiitiriiK and .1. S]n<i<iuc'ti 

 would necessitate the adoption of many more genera than most 

 systcraatists w'ould care to allow. In short, there are so many 

 species which, in their varying details of structure, seem to bridge 

 over so completely these ideally unimportant differences that, with my 

 present knowledge, I would not feel justified in separating them. 



