Abstracts

Presented by Kelly McLean - Email: kmclean6@unb.ca

Breeding American back duck populations (black duck; Anas rubripes) have declined range-wide since the institution of systematic surveys in the 1990s; however, what may be driving this decline is at present unknown. Black ducks can be intolerant to disturbance and may be subject to local threats, such as those from commercial forest harvesting. To determine if breeding black duck distribution is affected by commercial forest harvesting, we overlaid breeding black duck observations with historic forest harvesting patterns and wetland characteristics in New Brunswick (NB), Canada. Data were obtained from an existing systematic helicopter survey conducted in eastern Canada for 785 wetlands surveyed on a rotational schedule from 1995-2017. We determined for each wetland the proportion of intact forest in 30m and 1000m, the distance to the closest forest harvest within 1000m, the year of forest harvest, and forest harvest method for the most recent ten and twenty year periods. We then created a series of candidate a priori generalized linear mixed effects models; top candidate models for both the ten- and twenty-year disturbance periods were selected using AIC values. The proportion of intact buffer within 30 or 1000m did not influence the presence of breeding black ducks. Breeding black ducks were more likely to be observed on smaller wetlands; increasing wetland size had a strong negative effect on black duck presence. Increasing time since harvest and all harvest methods had negative effects on breeding black duck presence. Results were similar for the 10-year and 20-year time periods but decreasing distance to the nearest harvest had a negative effect on black duck presence in the 20-year model. Commercial forestry may have positive effects on breeding black duck presence following harvest which decrease over time. This may be caused by increased vegetation growth in regenerating forests, creating better nesting habitat.