Date of Award

5-2004

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

David A. Buehler

Abstract

Emergent plant communities at Reelfoot Lake were once dominated by giant cutgrass (Zizaniopsis miliacea). Cutgrass was used by relatively large numbers of secretive marsh birds, such as least bitterns (/xobrychus exilis). Water levels were stabilized in the early 1940s, which allowed cutgrass marshes to succeed to water willow (Decodon verticillatus) marshes. There is no information on the extent of water willow or its value to breeding birds on Reelfoot Lake. The objectives of this study were to 1) determine the extent and type of emergent plant communities on Reelfoot, 2) describe the breeding avian communities using these emergent plant communities, and 3) evaluate an interim nationwide secretive marsh bird monitoring protocol. During 2003, I used printed DOQQs to ground-truth emergent plant communities on Reelfoot. I determined that 93% of the emergent marsh was dominated by water willow. Cutgrass- and cattail-dominated marshes made up the remainder. Most marshes had a substantial amount of woody growth. Secretive marsh bird surveys and habitat data collection were conducted on Reelfoot and nearby Black Bayou during the 2003 breeding season. A total of 66 observations were made of 4 species during surveys, including least bitterns, pied-billed grebes (Podilymbus podiceps), common moorhens ( Gallinula chloropus), and king rails (Rallus elegans). American coots (Fulica americana) were also observed, but not during surveys. Logistic regression with stepwise selection found least bitterns were positively related to the percent cover of cutgrass (parameter estimate = 7.76, Wald chi-square = 4.70, P < 0.04). Over 90% of plots with􀁉 20% cutgrass had at least 1 least bittern. In contrast, only 50% of plots with< 20% cutgrass had at least 1 least bittern. A 20-ha cutgrassdominated unit on Black Bayou had greater species richness than surveyed areas on Reelfoot Lake. Apparent declines of secretive marsh birds on Reelfoot have coincided with the replacement of cutgrass by water willow. Songbird surveys and habitat data collection were conducted during the 2002 and 2003 breeding seasons. Several species of songbirds associated with closed-canopy forests were found in the marshes on Reelfoot. These birds were negatively associated with cutgrass (parameter estimate = -0.258, Wald chisquare = 5.19, P < 0.03) but positively related to percent cover of woody species (parameter estimate = 0.06, Wald chi-square = 2.85, P < 0.10). This indicates that as woody species increase at the expense of marsh vegetation, Reelfoot bird communities may shift from marsh-dependent species to those associated with closed-canopy fofests. If management for secretive marsh birds and marsh songbirds becomes a goal on Reelfoot Lake, vegetation manipulation may be necessary. A drawdown and possibly other management tools with the goals of replacing water willow with sparse stands of cutgrass and reducing woody vegetation may improve breeding habitat for many species of marsh-dependent birds on Reelfoot Lake.

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