Paul Ashley, Canadian Wildlife Service
Scott Petrie, Long Point Waterfowl and Wetlands Research Fund
Norm North, Canadian Wildlife Service
Matt Brock, CWS and LPWWRF
INTRODUCTION:
Waterfowl banding programs on Ontario are traditionally conducted in the summer when many species are readily caught and the age and sex can easily be determined. Some species however, including the American Black Duck (Anas rubripes), occur in relatively low concentrations during the summer banding period. Consequently, the cost of summer banding programs targeting Black Ducks can be substantial. More importantly, insufficient numbers of birds are captured to answer key questions pertaining to distribution, philopatry and age, sex, and condition-related mortality. This is problematic given the long-term decline in the continental population of Black Ducks.
Black Ducks concentrate at major staging areas like Long Point, Lake Erie (Figure 1) during migration. This provides an opportunity to increase our understanding of Black Duck mortality, movements, and condition if large numbers of birds can be banded (and weighed) at spring staging areas, particularly if age can be confidently discriminated.
Since insufficient numbers of Black Ducks are banded annually during conventional summer banding programs, the Canadian Wildlife Service and the Long Point Waterfowl and Wetlands research Fund embarked on a pilot project in 2000 to band Black Ducks during the spring at Long Point. Seventy-five Black Ducks were banded over a two-week period. In comparison, over 25 years of pre-season (summer) banding at Long Point, the Canadian Wildlife Service only banded 307 Black Ducks (x=12 per year)
It was determined the large numbers of Black Ducks could be captured and that they could be easily aged and sexed in the field by experienced banders. Juveniles were found to retain some immature middle and lesser coverts - they appear to retain them until the post-breeding molt (figure 2). Coloration of the feet and bill were also a good indicator of age (Figure 3). Using these characteristics, banders were confident in assigning age to birds.
In the spring of 2001, the program will focus on further refining and validating our aging techniques. All mallards and Black Ducks will be measured (3 structural measurements) and weighed so that we can ultimately make temporal, annual, age, sex and species-specific comparisons of condition. Whereas spring banding is somewhat unconventional, it certainly is not without precedent. Further, numerous banding studies have provided useful insight into waterfowl movement patterns, philopatry, as well as age- and sex-specific mortality rates by banding relatively small numbers (Less than 1000) of birds. Therefore, we feel that the initiation of a spring banding program at Long Point will provide a unique opportunity to increase our understanding of several key aspects of Black Duck staging ecology, movement patterns and survival.