502 J. A. ALLEN ON BIRDS 



Anatice. 



102. Anas boschas Linn. Mallard. Occasionally seen ; doubtless breeds in the State. 



103. Anas obscara Grael. Black Duck. Not uncommon in summer along the rivers and in 

 grassy ponds. 



104. Nettion carolinensis Bd. Green-winged Teal. Seen about ponds in August. 



105. Querquedula discors Steph. Blue-winged Teal. Observed with the preceding. 



106. Aix sponsa Boie. Wood Duck. Quite common. 



In spring and fall, geese, probably several species, and several other species of ducks are 

 reported to abound. I was also told that geese (probably Bernich canadensis Boie) breed in 

 considerable numbers in some of the grassy ponds in this part of the State. 



Larid^e. 



107. Hydrochelidon fissipes Gray. Sooty Tern. Seen in great numbers July 20, about 

 Wall Lake, in Sac County. The young had already flown, and were accompanying their 

 parents. Not seen elsewhere in our travels in this State. 



CoLYMBnm 



108. Podilymbus podiceps Lawr. Carolina Grebe. Seen in August in company with the 

 ducks above mentioned. 



n. Northern Illinois. 

 As my observations on the birds of Northern Illinois were made chiefly at two localities 

 one hundred miles apart, with an interval of time between, in which there was a considerable 

 change in the species represented, in consequence of the change in the season, I have 

 thought it best to give them under two distinct lists. The first of these lists, that of Ogle 

 County, 1 embraces only birds observed during the last three weeks of June, and consequently 

 only those breeding or fully settled for the summer. 2 This list includes probably more than 

 two thirds of the species that breed in the county, and nearly all that, from their number of 

 representatives, are characteristic of the district. The second list, that of Cook County, 

 though still less complete, and, from the earlier period of the observations (last half of 

 May), affording less valuable data on distribution, many of the species noticed being on 

 their passage northwards, is believed to furnish several points of interest. On comparing 

 these with lists for different localities in the Atlantic States for the corresponding period^ 

 considerable differences will be noticed ; especially in the comparative abundance o°f certain 

 species that are rarely or never met with on the Atlantic slope, under the same latitude. 

 Conspicuous among the first of these are Perissoglossa tigrina, Wilsonia pusilla and W. mitrata, 

 Helminthophaga peregrina, Vireo Philadelphicus, Euspiza amerieana, Melospiza Lincobui, Cenhinis 

 carolinus, and Phalaropus Wilsoni ; others more or less common here that are almost never 

 met with in the east are Colurio excubitoroides, Ckondestes grammaca, and Xanthocephahis idero- 

 cephalus, and also, in the breeding season, Eremophila alpestris. The occurrence of the latter 

 constitutes the more positive differences in the two regions, and marks the change in the 

 avi-fauna in passing from the primitively wooded districts to the prairies. 



l Ogle County is on Rock Eiver, about one hundred miles a We spent a few weeks here also in October ; but the few 



nearly due west from Chicago. Cook County borders on Lake notes made at that time, which are incorporated with the 



Michigan, and embraces Chicago within its limits. Evanston others, have the date of the observation distinctly stated, 

 was the principal point of observation in this county. 



