Sul Ross State University

Structure and Diversity of Avian Communities in Burned, Mixed and Unburned Sagebrush Steppe Habitats at Sheldon National Wildlife Refuge, Nevada

by Kristian K. McIntyre and Louis A. Harveson

In August 1999, a lightning strike sparked a wildfire burning over 15000 ha of sagebrush steppe in the southwestern section of Sheldon National Wildlife Refuge, Nevada. A Burned Area Emergency Rehabilitation (BAER) plan was implemented in 1999 as a guideline for site rehabilitation, habitat and wildlife monitoring.

In accordance with the BAER plan, the primary goals of this study were to

1. quantify and compare the distribution, abundance and diversity of birds in burned, mixed (patchy) and unburned habitat; and
2. investigate relationships between habitat structure and bird species occurrence in burned and unburned areas.

Avian community composition data was from a series of point count surveys within each of the three habitat types from 2000-2001. Annual variation in bird abundance and species richness was significantly different between the two years.

Species overlap occurred between burned, mixed and unburned habitat types. Sagebrush obligate species were found in greater numbers in unburned shrubland, while grassland species abundances were greater in burned habitats. Observed and extrapolated species richness were greatest within unburned habitats.

Species diversity, derived from Shannon H's and Fisher's α indices, was lowest in unburned habitats and similar between mixed and burned habitats. Species dominance (Simpson's 1/D) was similar between burned and unburned habitats and was lowest within mixed areas.

Gradient analyses were significant in explaining species-environment relationships. Percent cover of sagebrush, shrub height, percent area burned and the presence of mountain mahogany emerged as important factors in explaining variation in the bird species data.

Sagebrush obligate species and gray flycatchers were most indicative of unburned habitats with high shrub cover and greater shrub height.

Indicator species analysis revealed habitat shifts for six species of birds between 2000-2001. Avian community composition differed between burned, mixed and unburned habitat types each year.

Species-habitat relationships of shrubsteppe birds revealed within this study largely coincide with those described from similar studies. Additionally, species highly associated with sagebrush were especially vulnerable to habitat changes in sagebrush steppe as a result of the Badger fire.

Current and future management efforts regarding the high priority conservation of sagebrush and mountain mahogany communities within Sheldon National Refuge will ensure the continuation of man bird species on the refuge.

Funding provided by the United States Fish and Wildlife Service and Sul Ross State University.