
92 
lab technicians evidenced tentative presence of Clostridium botulinum but as this 
bacteria is a product of putrefaction its presence in live birds is not established. It 
was felt, however, that the rapid degree of decomposition of refrigerated birds indi- 
cated a diseased condition of some type. Weights of the two specimens were 1201.8 
and 1126.4 grams, and the stomachs of both contained a heavy percentage of Mya 
arenaria remains, It is obvious that the above-detailed specimens were collected too 
late in the breeding season for purposes of definite conclusions as to their particular 
status, 
"During May and early June of this year the writer assisted in waterfowl-crow 
studies conducted by the Canadian Wildlife Service on Prince Edward Island. On at 
least four of the Island's principal waterfowl areas (Black Pond Sanctuary; Clark's 
Brook; Dunk River; South Arm Dunk River) smaller concentrations of black ducks 
apparently identical in status to those studies on the Grand Pre-Canard were encountered, 
On May 14, at Black Pond Sanctuary, 69 blacks were observed feeding on exposed sand 
bars of Little Harbor pond, a sheltered saline cove immediately adjacent to the sanctuary 
proper. No tendency toward pairing could be noted and when flushed, the birds displayed 
characteristics peculiar to migrating blacks such as the writer witnessed at Tinker 
Harbor, Labrador, in September of 1949. On May 26 a similar group of 30 birds was 
tallied on the marsh at the mouth of Clark's Brook on the Upper Hillsborough River. 
"On June 2, 43 blacks were noted tipping and resting in the lee of a sand bar 
which projects into the breakers at the mouth of Black Pond outlet. When flushed, the 
birds took flight in a body and strung out into the wind in line formation with groupings 
of 5-14. One of the latter settled on Black Pond itself, and was studied at close range 
for approximately 20 minutes. Two of the component birds were females, the remain- 
ing eleven probably males. ; 
"Similar concentrations on the Dunk River proper and the South Arm of the 
Same added emphasis to the contention that the summering black duck phenomenon is 
neither localized geographically nor unimportant ecologically." 
Conclusion 
"Concentrations of summering black ducks have usually been explained in 
terms of groupings of adult males whose breeding functions were completed. The 
presence of females in numbers perhaps as high as 10-15 percent of the total of such 
flocks throws an entirely different light on the situation; if females are consistently 
present, or component males prove sexually inactive in other similar concentrations 
throughout the northeast, then considerable revision of present theories insofar as 
black duck breeding ecology may be in order. 
"The wide discrepancy between broods and adult birds observed in the Grand 
Pre-Canard areas has already been stressed, and it is obvious that the bulk of the 
brids comprising the flock studies in June could not have been breeding on these same 
marshes. The significance of this situation insofar as breeding ground censuses and 
brood production expectancy on basis of adult birds tallied is immediately obvious. 
The possibility of concentration from widely scattered areas in the Maritimes is 
conceivable, but aerial surveys in other Maritime habitats support the contention of 
heavy divergence between adult population and broods produced. Although summering 
black ducks are apparently mainly a saline marsh phenomenon (on the St. John River 
possible similar groupings were encountered on non saline areas) it would seem safe 
to assume that an explanation.on the basis of a concentration of post-breeding males 
and to a lesser extent, post-breeding females, requires further substantiation before 
acceptance. 
