Riparian Songbird Abundance a Decade After Cattle Removal on Hart Mountain and Sheldon National Wildlife Refuges

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. (In: Ralph， C. John; Rich， Terrell D.， eds. Bird conservation implementation and integration in the Americas: proceedings of the third International Partners in Flight Conference， March 20-24， 2002， Asilomar， California. Gen. Tech. Rep. PSW-GTR-191. Albany， CA: U.S. Dept. of Agriculture， Forest Service， Pacific Southwest Research Station: p.550-558)