OF NORTHERN ILLINOIS. 507 



Charadriid^;. 



73. JEgialitk vociferus Cass. Very common. 



ScOLOPACIDiE. 



74. Tringoides macidaiius Gray. Common. 



75. Actiturus Bariramius Bon. Very common, and quite unsuspicious. 



76. P/tilohela minor Gray. Abundant. 



77. Phaluropus Wilsoni Sab. As this species is known to breed in the Fox River and 

 Calumet marshes, it may well be included in the present list, though I did not actually 

 observe it. 



ARDEIDiE. 



78. Ardea herodias Linn. Rather common. 



79. Botaurns lentiginosus Steph. Common. 



80. Butorides virescens Bon. Common. 



81. Nyciiardea Gardeni Baird. Common. 



Rallid^:. 



82. Eallns virginianus Linn. Not uncommon. 



Anatid^;. 



83. Aix spoma Boie. Common. 



Probably a few Anas boschas and A. obscura breed in the more secluded marshes ; while 

 in spring and fall numerous species of ducks and geese occur in very great abundance. 



Larice. 



84. Hydrochelidon fissipes Gray. Common along the Fox River marshes. 



B. — Cook County. 



TuRDIDjE. 



1. Tardus migratorius Linn. Common. 



2. Tardus mustelinus Gmel. Very abundant, and rather easily procured. Not more shy 

 than the next. 



3. Turdus Swainsoni Cab. (T. Sivainsoni and T. Alicice Baird, Coues and others.) Very 

 abundant, and presenting its usual range of variation in color. 



Four additional seasons of investigation, with opportunities for a very careful examina- 

 tion of large series of both T. "Swainsoni" and T. "Alicia.'," sent to different museums by 

 the Smithsonian Institution, and chiefly labelled in Prof. Baird's handwriting, numbering 

 altogether more than twenty specimens, have fully confirmed the conclusions arrived at by 

 me from an examination of a great number of fresh specimens obtained in Massachusetts, 

 and published four years since in the Proceedings of the Essex Institute (Vol. IV, Aug. 

 1864, p. 56). These were, that the stage of plumage characterized as T. Alicice did not 

 form " even a well-marked variety," but that the two conditions of plumage, supposed 

 indicative of two species passed into each other by almost imperceptible gradations ; and 



