Conservation and Management

Populations of w. U.S. affected by intense grazing, especially where willow growth along riparian habitats is reduced or removed (Taylor and Littlefield 1986, Ohmart 1994). Counts along stretch of Salinas R. in Monterey Co., CA, declined 50% in 1980s; attributed to loss of riparian habitat and increase of Brown-headed Cowbirds (Roberson and Tenney 1993).

During migration, occasionally killed in collisions with TV towers and other tall, lighted structures, but relatively less often than most other migrant parulids. Early migration schedule may account in part for species’ rarity in fall tower kill samples, most during Sep and Oct, e.g., at TV tower in nw. Florida over 25 yr (1955–1980), 119 Yellow Warblers recorded, representing 0.3% of all birds killed and 0.7% of all warblers (Crawford 1981). No data on this species’ population response to environmental DDT.

Management of cattle grazing in w. U.S. to maintain willow borders of riparian habitats helps to hold Yellow Warbler populations (Taylor and Littlefield 1986). Yellow Warbler population density increased 6-fold within 2–3 yr after cessation of livestock grazing in se. Arizona riparian habitat (Ohmart 1994). For some populations, especially in sw. U.S. and certain islands in West Indies, brood parasitism by Brown-headed or Shiny cowbirds is a concern, in addition to habitat destruction. Cowbird management programs, specifically to aid Least Bell’s Vireo (Vireo bellii pusillus) populations in Riverside Co., CA, resulted in increased Yellow Warbler numbers (Gallagher 1997).