Using effigies to deter American crows and common ravens in snowy plover breeding habitat

Graduation Date

2013

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Natural Resources: Wildlife, 2013

Committee Chair Name

Mark A. Colwell

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Effigy, Threatened, Common Raven, Corvids, Non-lethal, Humboldt State University -- Theses -- Wildlife, Snowy Plover, Predator management, American Crow

Abstract

Common Ravens (Corvus corax) and American Crows (C. brachyrhynchos) are the principal predators of eggs and chicks of the Western Snowy Plover (Charadrius nivosus), which compromise population recovery of this federally listed species. I used a before-after/control-impact experimental design to examine the change in corvid activity in response to corvid effigies, a non-lethal predator control method. I conducted my study at Clam Beach, where corvids are more abundant than at any other plover breeding site in northern California. I conducted 18 trials, consisting of one "before" day and three days post-treatment, during the months of September through February. I recorded the average number and incidence of corvids that visited control and treatment plots within 1 m, 10 m, and 50 m of the center of the plot. Corvids were attracted to bait (trash and food) I placed in the study plots within 1-2 hours of the start of the experiment, and they continued to visit plots for four consecutive days (i.e., a trial). Effigies significantly reduced average corvid abundance and incidence (percentage of observations with at least one corvid) within a 50 m radius, but corvids still frequented plots. The effectiveness of effigies appeared to diminish over time; however this result was not statistically significant, and there was no significant difference in treatment effect among days 2, 3, and 4. I conclude that effigies may not be an effective predator management tool for deterring corvids in the vicinity of Snowy Plover nests.

https://scholarworks.calstate.edu/concern/theses/h702q884k

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