Bird-habitat relationships along a vegetation gradient in desert grasslands of the southwest

Abstract

During winter 1996-1997 and summer 1997, I studied bird assemblages along a vegetation gradient in desert grasslands of southeast Arizona and southwest New Mexico. A gradient of increasing woody cover and decreasing grass cover best described the variance in vegetation characteristics among sites. At larger scales of observation, I found woody plant characteristics had a large effect on the presence and distribution of individual species and assemblages. At finer scales of analysis, I found a greater proportion of relationships between birds and particular plant species. Bird species richness was positively related to shrub species richness during winter. I observed greater between season shifts in bird species richness among sites with >1.0% woody cover. Total bird abundance varied little between seasons except at sites with 1.0% woody cover. Woody plant levels below 10% and 20% are likely to increase populations of plains and semidesert grassland bird communities respectively.