Masters Theses

Date of Award

8-2008

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

David A. Buehler

Committee Members

Patrick D. Keyser, Arnold M. Saxton

Abstract

Grassland and shrub/scrub breeding birds have experienced severe population declines since the beginning of the Breeding Bird Survey in 1966 (Sauer et al. 2007). Habitat loss and degradation are likely the primary causes of decline (Herkert 1994, Warner 1994, Johnson and Igl 2001). Partners in Flight (PIF) continental population objectives call for managers to increase populations by up to 100% for several of the species found in the Big Barrens, north-central Tennessee and south-central Kentucky, such as Dickcissel (Spiza americana), Henslow’s Sparrow (Ammodramus henslowii), and Prairie Warbler (Dendroica discolor; Rich et al. 2004).

The quantity and quality of breeding season habitat are important in determining the future population trends of grassland birds throughout North America. Herkert (1995) identified the loss and degradation of breeding season habitat as the most likely cause of most population declines. It is important to determine the relative importance of habitat features for grassland birds on multiple scales in terms of population density as well as productivity. I compared population densities of breeding grassland birds in the Big Barrens with field characteristics (e.g. field size, vegetation measurements) to determine which habitat features promoted field use by each species (Chapter 2). I also monitored 39 Henslow’s Sparrow nests and 122 Field Sparrow nests in the Big Barrens during the 2006 and 2007 breeding seasons (Chapter 3). Estimates of Mayfield (1961, 1975) nest success were within the documented ranges for both Henslow’s Sparrow (23.8%, 95% CI: 10.7 – 40.5%) and Field Sparrow (15.4%; 95% CI: 9.5 – 23.1%). I also found evidence that Field Sparrows are at least double-brooded in the Big Barrens.

In addition to my work in the Big Barrens during the breeding season, we also sampled the winter bird community in the Big Barrens and in eastern Tennessee from 2003-07 using a variety of methods, including mist netting, widely dispersed point counts, rope dragging transects, and line transects (Chapter 4). My results indicated that a variety of habitats, including disturbed fields and agricultural fields in addition to grasslands dominated by native vegetation, is necessary to support the entire winter grassland bird community in the mid-South.

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