Document: KIM-3-53-4

Effects of thermal loading on the nest microclimate of ground-nesting birds.

SUEDKAMP, K.M*, F.SGUTHERY and S.DFUHLENDORF

Oklahoma State University, Stillwater, OK 74078 USA ¹

Abstract:
In semi-arid regions, thermoregulatory constraints may limit avian reproduction more than predator avoidance or food gathering strategies. Land management practices, such as livestock grazing, may further exacerbate thermal loading by reducing plant cover critical for moderating temperature fluctuations. Our objective was to evaluate the effects of grazing intensity (none, moderate, and heavy) on the thermal and structural properties of nests for seven ground-nesting bird species. We measured ground temperature, litter depth, and distance to visual obstruction at nest and random points monthly in each treatment during the 1999 breeding season. For species building cup nests, average maximum temperature was lower at nests compared to random points in the ungrazed and heavily grazed treatments, but higher at nests in the moderately grazed treatment. Average maximum temperature was higher at nests compared to random points in all treatments for birds that build scrape nests. Litter depth was higher at nests compared to random points for all species. Distance to visual obstruction was longer at nests compared to random points in the ungrazed and heavily grazed treatments for species that build cup nests, but was longer at nests in the ungrazed treatment for birds that build scrape nests. Our results show that birds with different nest building strategies select grazing intensities with different thermal and structural properties. Differences among nest-type guilds should be incorporated in future studies assessing grazing impacts on ground-nesting birds.

Keywords: grazing intensity, thermal environment, grassland birds, ground-nesting birds, nest microclimate

This abstract is being presented at: 10:45 AM in session:
Oral Session #3: Avian Ecology.