Traffic-Noise Impact Study for Least Bell's Vireo Habitat along California State Route 83

Abstract

A traffic-noise study was conducted to determine the impact that a highway reconstruction project would have on a habitat area for the least Bell's vireo, a federally protected songbird. FHWA and California Department of Transportation policies do not address the impact of noise on wildlife species; the study was conducted in response to a requirement of the U.S. Fish and Wildlife Service. Several mitigation measures were considered, including approximately 1200 m (4,000 ft) of temporary noise barriers. The outcome of the study was to provide funds for in-kind mitigation through habitat restoration rather than direct mitigation of noise impacts. This study contributes to a growing precedent of considering noise mitigation specifically for the protection of wildlife and raises several policy issues. Despite the increasing number of noise-mitigation projects for endangered birds and the commitment of significant funds to these undertakings, there remains a lack of firmly based noise-impact criteria and guidelines for noise mitigation.

A before–after control–impact assessment to understand the potential impacts of highway construction noise and activity on an endangered songbird

“…The USFWS previously indicated that noise levels occurring at ≥60 dB(A) during the loudest hour of the day may negatively influence songbirds (Barrett, 1995;Dooling & Popper, 2007). However, the USFWS also recognizes that species respond differently to noise depending on their life-history traits and the level and persistence of noise exposure.…”