Riparian Songbird Abundance a Decade after Cattle Removal on Hart Mountain and Sheldon National Wildlife Refuges
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Cattle were removed from the high desert riparian habitats of Hart Mountain and Sheldon National Wildlife Refuges in 1990. This study compares songbird abundance in 2000-2001 to that in 1991-1993 on 69 permanent plots. Of the 51 species for which detections were sufficient to calculate changes in abundance, 71 percent (36/51) exhibited a positive trend and 76 percent (16/21) of species exhibiting a significant change (either positive or negative) increased. The average increase among the 51 species was equivalent to 3.0 detections/km². Increasing species included species of concern in the Columbia Plateau: Yellow Warbler (Dendroica petechia), White-crowned Sparrow (Zonotrichia leucophrys), Song Sparrow (Melospiza melodia), Dusky Flycatcher (Empidonax oberholseri), Warbling Vireo (Vireo gilvus), Mourning Dove (Zenaida macroura), MacGillivray’s Warbler (Oporornis tolmiei), and Orange-crowned Warbler (Vermivora celata). Aspen and willow associates, but not meadow associates, exhibited a significant increase in detections/ km². Detections of ground/low cup and high cup nesting species, but not cavity nesting species, increased significantly. Ground/understory foraging species, aerial, and overstory foraging species increased significantly in detections/km², but bark gleaning species did not. For the 16 significantly increasing species in this study, patterns of change on Breeding Bird Survey routes during 1980-1999 suggest that the changes documented here are not merely a reflection of regional patterns.