The Influence of Grazing Systems and Grazing Intensity on Nongame Birds in North Dakota Grasslands

Eric D. Salo and Kenneth F. Higgins, South Dakota Cooperative Fish and Wildlife Research Unit, USGS/BRD, and Department of Wildlife and Fisheries Sciences, South Dakota State University, Brookings, SD 57007

Table of Contents

• Introduction
• Methods
  • Bird Surveys
  • Vegetation Sampling
• Preliminary Results
• Acknowledgements

Introduction

All of the grazing systems studied by Messmer were located on native mixed-grass rangeland at the CGREC. In the third study Kennedy (1994) examined the effects of grazing on nongame birds, insects, and vegetation on three treatments and idle areas in tame grasslands under Conservation Reserve Program (CRP) contract. Treatments studied by Kennedy included a three-pasture, twice-over rotation system, season-long grazed pastures, hayed treatments, and idle areas.

Vegetation planted in the CRP grasslands include a mixture of tall wheatgrass (Agropyron elongatum), intermediate wheatgrass (A. intermedium), smooth bromegrass (Bromus inermis), yellow sweetclover (Melilotus officinalis), white sweet- clover (M. alba), and alfalfa (Medicago sativa).

The CRP demonstration project is located in Stutsman County about two miles west of Streeter, North Dakota and about 5 miles southeast of the CGREC. Some of the grazing systems studied by Messmer and Kennedy have been managed the same way for nine or more years and offer a chance to study the long-term effects of these grazing regimes on bird use.

In 1989, the CGREC started conducting grazing intensity studies in native mixed-grass rangeland including light, moderate, heavy, and extreme treatments (Patton et al. 2000). These study plots offer the chance to study the effects of grazing intensity on nongame bird use.

In the spring of 2001 our research project was initiated to determine the temporal effects of grazing regimes and the effects of grazing intensity on nongame bird use. Idle areas during this study, which were chosen to compare bird use with grazing treatments, are located on Waterfowl Production Areas managed by the U.S. Fish and Wildlife Service’s Kulm Wetland Management District and Long Lake National Wildlife Refuge. The objectives of this study are:

1.         To determine if there is any change in species composition and breeding bird densities due to temporal effects of grazing treatments.

2.         To determine if there is any change in vegetation structure due to temporal effects of grazing treatments.

3.         To determine the differences in avian species composition and breeding bird density in pastures with different grazing intensities.

Methods

Bird surveys were conducted from May 15 to July 15, 2001 along permanent, systematically placed belt transects of fixed length (100 to 200 m) and width (100 m) (Wakeley 1987). Surveys started around sunrise and were conducted until 10 am on days when wind speeds were less than 20 km/h and when there was little or no precipitation. During each survey the observer walked at an approximate speed of 1.0 to 1.5 kph and recorded birds in the belt transect using visual and auditory cues. After each transect survey was completed the observer also did a 15 minute “walk-about” around the treatment area to document all nongame bird species present in the treatment area, including the belt transect area.

Vegetation Sampling

Preliminary Results

Avian species richness (the number of species per survey plot represented by one or more birds) values ranged from 4 to 12 per belt transect and from 8 to 17 on walk-abouts (Table 1). Avian species richness values were generally lower in CRP demonstration plots than in plots in native mixed-grass grasslands. This could be due to the more homogeneous nature of the CRP plantings. However, we caution that these are preliminary analysis values and have yet to be adjusted for vegetation differences. So far, it appears the higher avian species richness values coincide with plots containing ample buckbrush (Symphoricarpos occidentalis) clumps and the fact that some shorebirds (e.g., killdeer, willets and godwits) prefer shorter grassland vegetation in which to nest.

All 2001 bird and vegetation survey data will be analyzed this winter. All surveys conducted in 2001 will be repeated in 2002 after which a final report of findings will be presented in the form of a Master of Science thesis.

Acknowledgements

We thank Paul Nyren and the Central Grasslands Research Extension Center staff for assistance with this study. Funding in 2001 was provided by the Renewable Resource Extension Act (RREA) funds via South Dakota State University with Larry Tidemann’s assistance. The South Dakota Cooperative Fish and Wildlife Research Unit and the Wildlife and Fisheries Sciences Department at South Dakota State University in Brookings provided additional support for this project. Dr. William T. Barker offered advice and direction to the study before the onset of the field studies in 2001; we thank him for his input.