November, IQ44 



Bellrose: Duck Populations and Kill 



369 



figures 



during 



sation 



When 



end of 



ducks 



be abl 



on peak numbers of each species 

 the season, without any compen- 

 for turnover of the populations, 

 banding data are analyzed to the 

 showing the rate of movement of 

 through the valley, then we shall 

 e to determine fairly accurately 



indicate that during the 1938-1942 

 period, 3.3 per cent of the ducks of all 

 species in the Illinois River valley were 

 taken by hunters, table 16. The band 

 return data may be too low in some 

 years because of a disproportionate 

 amount of late season banding. After 



Table 16. — The approximate per cent of ducks bagged in the Illinois River valley, 



1938 1942. 



*Only mallard, black duck and pintail. 



the number of ducks that actually pass 

 through the Illinois River valley. 



The ratio between the number of 

 ducks banded each year on the Chautau- 

 qua National Wildlife Refuge near 

 Havana and the number of returns from 

 them in Illinois during the same season 

 should indicate the minimum per cent 

 of kill. Since only the mallard, black 

 duck and perhaps the pintail were 

 banded in sufficiently large numbers to 

 be significant, the band return figures 

 apply principally to those species. The 

 figures indicate a minimum kill ranging 

 from 1.8 per cent of the flight in 1939 

 and 1941 to 5.0 per cent in 1940, table 

 16. There is a greater annual variation 

 among the banding ratios obtained than 

 among the figures obtained from a com- 

 parison of the population-kill data. 

 This is due probably to the fact that 

 the chronology of banding did not cor- 

 respond to the chronology of migration. 

 The low per cent of 1.8 in 1939 and 1941 

 occurred as the result of a dispropor- 

 tionate number of birds being banded 

 late in the season; the banded birds, 

 therefore, received less shooting pres- 

 sure than the population as a whole. 



Population-kill figures for all ducks 

 tend to verify the band recovery data, 

 which were principally for mallards, 

 black ducks and pintails. These figures 



making allowances for inaccuracies in 

 data, we estimate that, in the period of 

 this study, Illinois hunters annually 

 harvested between 3 and 5 per cent of 

 the duck flight passing through the 

 state. 



Total Effect of Regulations 



The cumulative effect of federal 

 regulations on the continental take of 

 ducks in the past decade may perhaps 

 best be measured by ratios of first- 

 season band returns to birds banded. 



A study of data presented by Lincoln 

 (1924) reveals that of about 1,330 mal- 

 lards banded near Browning, Illinois, in 

 the fall of 1922, approximately 20 per 

 cent were killed before the end of the 

 hunting season. The Illinois Natural 

 History Survey duck banding program 

 was begun almost 20 years later, after 

 important federal restrictions had been 

 placed in force. Banding was done on 

 the Chautauqua National Wildlife Ref- 

 uge, near Havana, some 20 miles north 

 of Lincoln's station, usually from Oc- 

 tober until the freeze-up in early De- 

 cember. Notwithstanding the fact that 

 we banded on a refuge, the high pro- 

 portion of local returns demonstrated 

 that the ducks we banded suffered a high 

 local kill. Yet the same-season band 



