A rapid decline in cormorant numbers has occurred since 1950. By 

 1965 only 22 cormorants were observed on an aerial inventory of water 

 birds in the Illinois River valley. Between 1965 and 1972 cormorants 

 were only observed once during the fall waterfowl census flight of 

 the Illinois and Mississippi River valleys made by the Illinois Natural 

 History Survey. In recent years a gradual increase in cormorant num- 

 bers has occurred in Pools 24, 25, and 26 of the Mississippi River 

 (Table 47). 



The cause for the dramatic decline in cormorant numbers is not known 

 at this time. However, the implementation of the nine-foot channel 

 appears to have had little effect on the cormorant. 



Shorebirds and Related Species 



At times large numbers of shorebirds, gulls, and terns, members 

 of the order Charadriif ormes , occur within Pools 24-26. Shorebirds 

 are most abundant from mid-summer through early fall when mud flats 

 are exposed by receding water. This condition is prevalent only in 

 those summers that river flows are minimal. 



Three areas within the project area are noted for shorebird con- 

 centrations: (1) Lake Meredosia on the Illinois River at the upper 

 end of Pool 26, (2) Calhoun Refuge, a short distance above the mouth of 

 the Illinois River, and (3) Batchtown area, at the lower end of Pool 

 25. 



A list of the occurrence of shorebirds and gulls on the three areas 

 is shown in Table 48. The most abundant sandpipers are the following: 

 pectoral, least, semipalmated, and lesser yellowlegs. Other important 

 shorebirds are killdeer, woodcock, and common snipe. 



Gulls are many times more abundant than terns, which occur late 

 in the spring and early in the fall. On the other hand, gulls are most 

 numerous from mid-fall through mid-spring. During this period many 

 thousands occur within the project area. Ring-billed gulls composed 

 the bulk of the birds, followed by herring gulls. 



Increased sedimentation has resulted in the filling of marshy areas 

 creating shallows which are exposed during the low water in summer and fall. 



168 



