Does Restored Riparian Habitat Create Ecological Traps for Riparian Birds Through Increased Brown-Headed Cowbird Nest Parasitism?

Abstract

A growing concern among restoration ecologists is inadvertently creating ecological traps, yet identifying ecological traps is difficult, particularly over a large region and for an entire suite of species. Here we use an example to show that restoration ecologists can evaluate the risk of creating ecological traps. We reviewed the literature and synthesized data to evaluate the risk that restored riparian forests create ecological traps for riparian birds by attracting dense populations of the brood parasite, Brown-headed Cowbird (Molothrus ater; hereafter cowbird) in the Central Valley of California, U.S. We found that most riparian bird populations are not highly vulnerable to cowbird parasitism, that there were no differences in cowbird density or parasitism rates between restored and remnant riparian forests, and that the riparian bird community responded positively to restoration. We concluded that riparian restoration in California’s Central Valley has a low risk of creating ecological traps through cowbird parasitism. We recommend that restoration ecologists consider the potential for creating an ecological trap early and throughout the restoration design and implementation process, and include plans to monitor species responses to restoration, both in restored areas and in source populations nearby, as well as any specific conditions associated with a potential trap.