93 
"The possibility that a heavy percentage of both males and females encountered 
in such relatively static groups of blacks may be non-breeding birds can hardly be dis- 
missed. Atno time during the study was anything approximating sexual activity observed, 
and while studies were undoubtedly begun late in the breeding season it would seem 
natural to expect some such displays in large groups containing both unmated males and 
females. 
"A discussion of reasons for non-breeding can at the present time involve 
little more than speculation: whether the birds may be sexually immature (not breed- 
ing in first year); adults sterile because of lead poisoning or other cause; adults sexually 
mature but non-breeding because of lack of suitable nesting habitat; immatures unsuccess- 
ful in mating or combinations of any above is something only further studies can reveal. 
’ To insure establishment of a full case history such studies should begin on sample areas 
no later than April 1-15, and continue at least at regular intervals until about August 1, 
of any breeding and post-breeding season. Collection and competent pathological analysis 
of a number of specimens sufficient to guarantee validity of data would appear an essential 
component of any further investigations. Banding of birds from these flocks where feas- 
ible (possibly at Black Pond Sanctuary, Prince Edward Island) would provide interesting 
but perhaps not essential information. The markings of sample individuals (by airplane 
dope or other feasible method) would be a decided aid to study." 
