Type of Document Master's Thesis Author Arquilla, Brian Joseph URN etd-04102007-120515 Title Effects of Predator Activity on the Nesting of American Black Ducks and Other Birds on Barrier Islands in the Mid-Atlantic Coast Degree Master of Science (M.S.) Department Renewable Natural Resources Advisory Committee
Advisor Name Title Frank Rohwer Committee Chair Michael Chamberlain Committee Member Phil Stouffer Committee Member Keywords
- predation risk
- nest density
- nest success
- predator activity
- virginia coast reserve
Date of Defense 2006-04-15 Availability unrestricted AbstractLandscape change throughout North America has resulted in heightened nest predator population and declining avian productivity. Essential to establishing effective management design is an understanding of differential predation pressure among avian groups as group specific responses to predation impact may exist.
The objective of this study was to examine the efficacy of predator trapping on the nest success and density of ground nesting avifauna in 2004-2005 in the Virginia Coast Reserve, specifically dabbling ducks, Canada Goose and Willet. Second, we determine the impact of predation on ground nesting birds by relating indices of predator abundance to nest density and nest success for island plots.
Overall Mayfield nest success for dabbling ducks was 54.4% (n = 12) in 2004 and 17.7% (n = 30) in 2005. Green Transformed nest success for dabbling ducks was 34.5% (n = 25) in 2004 and 23.0% (n = 42). For Canada goose, overall Mayfield nest success was 53.1 (n = 37) in 2004 and 47.7% (n = 39) in 2005. Overall Green Transformed nest success for Canada Goose was 59.5% (n = 57) in 2004 and 50.6% (n = 51) in 2005. Finally, overall Green Transformed nest success for Willet was 53.7% (n = 110) in 2004 and 46.0% (n = 118) in 2005.
Nest success estimates on island plots varied greatly. There was no difference in nest success between trapped and non-trapped islands for dabbling ducks (P = 0.1990), Canada Goose (P = 0.4860), Willet (P = 0.4920) and artificial nest success (P = 0.4200). Likewise, there was no difference in nest density between trapped and non-trapped islands for dabbling ducks (P = 0.2408), Canada Goose (P = 0.2950), and Willet (P = 0.1381). Several factors may explain this result including a lack of trapping efficacy, design flaws, low intensity of trapping, and differences in island habitat affecting avian nest site selection and sample size.
Nest success for both dabbling ducks (P = 0.0225) and Willets (P < 0.0001) was inversely related to predator activity, as measured by artificial nest success. In contrast, Canada Goose (P = 0.6686) showed no relationship between nest success and predator activity. For Canada Goose (P = 0.0064) and Willet (P = 0.0029), nest density decreased with increasing predator activity on island plots. Biased nest detection, philopatry to islands with reduced predation risk, and active selection for reduced predator environments may explain the higher nest density on islands with reduced predator activity.
On barrier islands in Virginia, dabbling duck nest densities are independent of predator activity (P = 0.1981). I hypothesize that, in this system, the availability of brood rearing habitat for ducks govern island selection above predation risk.
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