Date of this Version
THE PRAIRIE NATURALIST, Volume 37, No. 1, March 2005, pp 21-28.
We compared the effects of two different nest placement strategies (shrubs vs. bunchgrasses) on microclimate conditions for grasshopper sparrow (Ammodramus savannarum) and lark sparrow (Chondestes grammacus) in Oklahoma. We predicted that the intensity and duration of extreme temperatures (greater than 39° C) and their variability would be reduced at shrub nests compared to bunchgrass nests. A verage maximum temperatures were similar at nests of grasshopper sparrow and lark sparrow, but confidence intervals were more variable and included biologically detrimental temperatures at grasshopper sparrow nests compared to lark sparrow nests. The proportion of time greater than 39° C also was similar at nests of both species, but on average grasshopper sparrow nests exceeded 39° C for 1.2 hr compared to 2.6 hr per 29-hr sampling period for lark sparrow nests. Our results indicate shrub nesters (lark sparrow) might be able to moderate the intensity and duration of biologically detrimental temperatures at their nests more successfully than bunch grass nesters (grasshopper sparrow).