VoI. 25, No. 6 
Page 4 
. / eak numb ® r s of 117,000 Canada geese, approximately 3,000 of which were the 
giant race, and 7,*00 snow geese were present in the Illinois Valley during 
and°^ Qno 982 ' The Mls i[ ss * pp ' vaney hosted peak numbers of 20,300 Canada geese 
and 3,900 snow geese. The Canada goose peaks for the spring migration were 3 to 
4 times the abnormally low numbers for the previous spring of 1981, but had not 
yet rebounded to the peak levels for the 1980 spring migration. 
. rInn /a f e n° W ! Sta Y Jn *l linols for a shorter time during spring migration than 
9 m ' 9rat ' 0n - Goose concentrations decreased abruptly by mid-March of 
1982 , and duck numbers were declining by mid-April. Common goldeneyes and 
common mergansers, which overwinter in Illinois, are the 1st species to depart 
tor the northern breeding grounds. Geese are also early migrants, followed by 
such dabblers as pintails, mallards, black ducks, and wigeon, some of which spend 
the milder.winters in Illinois. The majority of the diving ducks arrive about 
midway during the migration season; canvasbacks and redheads are the 1st to 
appear and scaup and ruddy ducks are the last to leave. The latest spring 
migrants are blue- and green-winged teal and northern shovelers. 
Many factors cause the timing and duration of the spring migration to vary 
from year to year: inconsistent spring weather (probably the most important 
factor), water ,eve Is and food conditions (which are partially dependent upon 
weather), and the physiological readiness of the birds to migrate. 
. ^unusually harsh winter and spring in Illinois in 1981-82 delayed the 
», m ' 9 :! tl0n 2 " 3 Weeks ln comparison with the mild winter and spring of 
Harrh anri } ^ °" Set ° f 1982 ' 5 spring migration, high water levels during 
March and April and poor food conditions (MWRL 24(11):*) encouraged a rapid 
migration through Illinois. Water conditions on the breeding grounds in the 
prairie pothole region are generally more favorable than last year. 
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