Vol. 24, No. 9 
Page 4 
329-30 
SA 
F 
17.5 
23.0 
SW 
4/15/31 
5/12/01 
334-35^- 
SA 
M 
8.5 
13.6 
SW 
4/23/31 
5/01/31 
338-39 
A 
F 
8.3 
13.3 
N 
4/24/81 
5/01/31 
245-46 
SA 
F 
7.0 
11.2 
NE 
5/03/31 
5/06/81 
247-43 
A 
F 
7.0 
11.2 
NE 
5/03/81 
5/06/31 
^Age: 
A « >1 
year 
; SA - <1 
year 
^.ast 
seen on 
the 
S edge of 
Champaign, 
Champaign 
Co. s 111., 
16 June 1931 
^Returned to AHerton Park 6 May 1931 but remained on the opposite side of 
the Park from his winter range. 
» 
Cooperative V/aterfowl Research - W-G3-R F.C. Rellrose, S.P. Havera, 
H.A. Perkins, H.K. Archer 
Aerial waterfowl censuses conducted by Robert Crompton provide valuable 
information about waterfowl species that are abundant as migrants in Illinois. 
These cen-ejjses also provide an opportunity to monitor uncommon waterfowl species 
and other avian species associated with the rivers and the adjacent bottomland 
lakes. Among the uncommon waterfowl species occasionally observed durtng the 
aerial censuses are the mute and whistling swans. The exotic mute swan was 
introduced and became locally established in North America. Mute swans have 
been observed numerous times in the Illinois Valley during the falls of 1977 
through 1979 and were observed once in the Mississippi Valley during the fall of 
1977* The largest total number of mute swans counted in the Illinois Valley for 
an entire fall was 209 in 197*; the peak number counted on a single flight was 
36 on 26 September 197^. 
Whistling swans are rarely seen in Illinois, only 6 were sighted from 19/6 
through 1379. However, a total of 94 were counted in the Mississippi Valley 
during late March, early April, and late October of 1930. The largest number of 
whistling swans seen on a single flight in recent years was 4G on 17 April 1930. 
Double-crested cormorants and white pelicans are also counted during aerial 
censuses. The cormorant is on Illinois' endangered species list but often is 
seen in the Illinois and Mississippi valleys during fall and spring migrations. 
Until the mid-1950's, the double-crested cormorant was a common migrant and a 
fairly common nester in the Illinois River valley. An estimated 15,000 migrants 
were counted in the Illinois Valley on 16 October 1950. Dy 195 > s the great 
passages of cormorants had dwindled to a small flight of 300 individuals. Ho 
birds were counted between 1966 and 1973. Their numbers have been on the increase 
