Master's Theses

Department

Biology

Degree Name

Master of Science (MS)

Abstract

Grassland birds have declined more rapidly than any other avian taxa in North America. While woody encroachment is often cited as a threat, some grassland-dependent species requiring habitat with scattered trees or shrubs also are declining at statistically significant rates. To better understand the ecological costs and benefits of woody vegetation from a brush management perspective, I studied bird-habitat associations along a canopy cover gradient of eastern red cedar (Juniperus virginiana). Habitat associations were tested by the comparing the relative abundance of breeding birds between 3 habitat treatment levels (0% eastern red cedar canopy cover [open grassland], < 5% eastern red cedar canopy cover [light encroachment], and > 5-25% eastern red cedar canopy cover [moderate encroachment]). Data were collected by repeated point count sampling in mixed-grass and sand prairie habitats of Barton County, Kansas from 2011 to 2012. At the community level, bird response patterns were attributed to habitat preferences and nest placement. Ground-nesting species associated with grassland-forb habitat were most abundant in open grassland sites and decreased with increasing eastern red cedar canopy cover. In contrast, species associated with grassland-shrub and savanna habitats were associated positively with eastern red cedar canopy cover. Patterns in the bird community were further examined with cluster analysis and non-metric multidimensional scaling. Avian species-level responses were assessed with canonical correspondence analysis, which indicated that eastern red cedar canopy cover explained most of the variation in the bird abundance. Abundance models and analysis of variation (ANOVA) further elucidated the significance of response patterns and species distributions along the canopy cover gradient. Considering the diverse habitat requirements of grassland birds, resource managers should consider how conservation practices for one species might affect others.

Keywords

eastern red cedar, grassland, succession, community similarity, indicator species, bird-habitat association, species of greatest conservation need, brush management

Advisor

Dr. Elmer J. Finck

Date of Award

Spring 2014

Document Type

Thesis

Rights

© The Author(s)

Comments

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