Which Bird Species Groups Use Highway Roadside Verges and Why?

Abstract

Highway roadside verges (HRV) provide supplemental habitat for birds in intensive agricultural and suburban landscapes where the natural habitats are rapidly disappearing. The purpose of this study was to document the behavior of breeding bird species using the vegetation maintenance units (green shoulders, embankments, ditches, and banks) of HRV in 3 typical rural landscapes of southern Quebec, Canada. We observed the behavior of 722 individuals of 21 bird species. The most abundant ones (especially Sturnus vulgaris [European Starling] and Agelaius phoeniceus [Red-winged Blackbird]) foraged in the green shoulders, while others (such as Melospiza melodia [Song Sparrow], Spinus tristis [American Goldfinch], and Geothlypis trichas [Common Yellowthroat]) travelled or nested in the low vegetation in ditches and on the banks. Omnivorous species forage in the green shoulders and used the banks and ditches mainly for nesting-related behaviors, just like the few insectivorous species observed. The granivorous species were almost absent from studied HRV. Ground-foraging species used the shoulders to feed but nested in ditches and banks. Species foraging in low vegetation foraged mainly on the banks and used the ditches more for travelling. Reducing the mowing frequency of these 2 maintenance units would likely result in an increase in the vegetation cover and would thus provide additional nesting and foraging habitat for the species we recorded, 67% of which show a stable or declining population in North America.