During winter 1996–1997 and summer 1997, we surveyed birds at 26 study sites in desert grasslands of Arizona and New Mexico to determine tolerance of birds to variability in plant composition and structure. The relationship between bird abundance and vegetative characteristics might be an important consideration in the development of management and restoration plans. Of the 49 bird species we observed, we examined 13 and 16 species in detail for winter and summer seasons, respectively. A noticeable shift in species composition occurred between 3% and 10% woody plant cover. During winter, Chestnut-collared Longspurs (Calcarius ornatus) and Horned Larks (Eremophila alpestris) showed significant positive relationships with grass cover and negative relationships with woody plant cover, occurring in greatest numbers where woody cover was <1%. The richness of sparrow species during winter was highest among sites with 6% to 15% woody plant cover. In addition to showing significant positive relationships with woody cover, Vesper Sparrows (Pooecetes gramineus), Black-throated Sparrows (Amphispiza bilineata), Brewer's Sparrows (Spizella breweri), and Chipping Sparrows (S. passerina) showed significant positive relationships with shrub species richness. Our results showed that reductions of woody plant cover below 3% in combination with the presence of native grasses could substantially enhance the presence of several bird species. Maintenance of woody cover between 6% and 15% could increase use by a suite of other species, especially wintering sparrows.
Block, Giselle and Morrison, Michael L.
"Large-scale effects on bird assemblages in desert grasslands,"
Western North American Naturalist: Vol. 70
, Article 3.
Available at: http://scholarsarchive.byu.edu/wnan/vol70/iss1/3