Capturing Crows for the Protection of Threatened and Endangered Shorebird Species

Abstract

ABSTRACTCorvids are highly intelligent and capable of thriving in anthropogenic ecosystems. American crows (Corvus brachyrhynchos) regularly depredate threatened and endangered avian species. Live capture is a common component of crow management programs; however, crows are notoriously difficult to capture. Here, we report previously undocumented crow capture techniques, utilizing a modified goshawk (Accipiter gentilis) trap design as part of a shorebird conservation project in San Diego, California, USA, 2012–2017. A negative binomial generalized linear model showed a significant relationship between number of crows removed and number of endangered California least tern (Sternula antillarum browni) eggs predated by crows. Of the total number of crows in that analysis, 67% were removed via goshawk trap. Therefore, we attribute the same percentage of reduction in egg loss to the success of that trap type. We tested 2 goshawk trap designs that differed by number of capture chambers (single and double). Double‐chambered traps were nearly twice as effective at capturing crows compared with single‐chambered traps. We performed McNemar's χ2 tests with continuity correction to determine whether traps were more effective with the use of conspecific lure‐birds and obtained significant results for single and double‐chambered traps. The modified goshawk trap has an efficient design that can improve crow control programs, especially when constructed with 2 chambers and deployed with lure‐birds. © 2018 The Wildlife Society.