Table 1. Periodic inventories of Canada geese, Swan Lake National Wildlife Refuge and Swan Lake Zone, 1975-78. 
(Data from Missouri Department of Conservation, Columbia, Missouri.) 


Date Refuge Zone Date Refuge Zone Date Refuge Zone 



(1975-76) total total (1976-77) total total (1977-78) total total 
29 Sep 50,075 51,725 9 Sep 21,700 42,750 27 Sep 2,150 2,150 
6 Oct 79,325 99,850 12 Oct 77,400 92,300 3 Oct 42.000 42.500 
20 Oct 136,125 166,475 25 Oct 140,500 179,200 11 Oct 36,250 39,250 
27 Oct 108,000 185,000 1 Nov 146,600 169,625 17 Oct 79.600 108,250 
10 Nov 145,900 173,925 8 Nov 147,800 175,200 26 Oct 104,200 113,250 
17 Nov 154,850 171,350 15 Nov 149,900 170,025 7 Nov 106.800 111,650 
1 Dee 101,650 196,000 22 Nov 162,900 179,675 14 Nov 125,700 137.900 
15 Dee 36,500 174,600 29 Nov 177,725 195,825 21 Nov 98.600 116,175 
5 Jan 300 180,025 13 Dec 66,600 211,375 28 Nov 156,000 164,650 
20 Dec 43,450 197,225 12 Dee 80,100 120,600 
5 Jan 10,350 160,125 19 Dec 107.300 157,950 
3 Jan 181,300 224 O00 

tion (late February through March), the ratio of adults to 
immatures was greatest during the periods of harshest 
weather and low food availability on the refuge. 
In 1977-78, after the December peak, numbers of im- 
matures declined somewhat and then remained nearly 
stable until mid-January, when they increased and made 
up 70% of the eagle population on the refuge. Percentages 
of adults ranged from 30 to 45 during mid-December to 
mid-January and from 35 to 68 during mid-January to 
mid-March. However, the percent increase in March 
occurred while total numbers of eagles were declining. 
From mid-January to early March, numbers of immature 
eagles in the population gradually decreased. Numbers 
then remained relatively stable until birds left the refuge 
in late March. Age ratio patterns and total eagle 
population numbers were relatively more stable during 
this field season than in 1975-76 and 1976-77. 
Canada Goose Populations 
Migrant waterfowl began arriving in the Swan Lake 
Zone in mid-September, remained throughout winter, 
and left in March. During this study, 32 aerial Canada 
goose inventories were conducted by the Missouri Depart- 
ment of Conservation from September to early January: 9 
in 1975-76, 11 in 1976-77, and 12 in 1977-78 (Table 1). 
Canada goose populations on Swan Lake NWR in the 
successive field seasons peaked at 154,850 birds on 17 No- 
vember 1975; 177,725 on 29 November 1976; and 181,300 
on 3 January 1978 (Table 1). Peaks for the entire Swan 
Lake Zone came 2 weeks later in 1975-76 and 1976-77, 
and on the same date in 1977-78 (Table 1). 
Waterfowl distribution and concentration in the Swan 
Lake vicinity were affected by weather, habitat conditions 
(including water and food availability), and hunting pres- 
sure. After the waterfowl hunting season began, geese con- 
centrated on the refuge, but after closure of the hunting 
season, onset of severe winter weather, or depletion of 
food supplies, they moved to the Missouri and Grand 
rivers or to other locations outside the Swan Lake Zone. 
However, when standing corn and milo were mowed on 
the refuge in January each year, waterfow! concentrated 
in these fields, where the grain had previously been largely 
inaccessible to them. Large numbers of waterfowl used 
the refuge briefly during the spring migration in March. 
Carcasses of Waterfowl and Fish Available 
Canada goose crippling loss from waterfowl hunting in 
the Swan Lake area was estimated to be 20% of the total 
harvest by Vaught and Kirsch (1966). Consequently many 
crippled and dead waterfowl are concentrated on and 
near the refuge. Many crippled geese die in fields or in im- 
poundments, where they wash ashore, Their numbers are 
augmented by diseased birds. Our waterfowl carcass 
counts along a transect yielded relative numbers of water- 
fowl carcasses available to eagles. We made 10 such counts 
in 1975-76 and 15 in 1976-77 (none in 1977-78; Table 2). 
Each year the goose hunting season opened in late Octo- 
ber (25-29 October during our 3-year study), and lasted 
until the goose harvest quota for the Swan Lake Zone or 
the scheduled end of the goose hunting season was reached 
(usually early December; early January in 1977-78). 
Approximately 25,000 geese were harvested in 1975-76, 
and 20,000 in 1976-77 and 1977-78. 
In 1975-76, 11 waterfowl carcasses were seen along the 
refuge transect on 20 October when the first count was 
made; numbers increased rapidly to a peak of 89 on 
4 November, and then decreased to nil by 11 January. 
In 1976-77, 6 carcasses were seen on 6 November, 14 on 
28 November, and (after freezing weather and snow) 2 on 
14 December. Carcass numbers then rose to 28 by 
18 December, after waterfowl use of the refuge had in- 
creased during warm, thawing weather, and snow- 
covered carcasses became visible as the snow melted. Car- 
cass numbers then declined to zero by 7 January. Again, 
