Masters Theses

Date of Award

5-2009

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

Matthew J. Gray

Abstract

Mudflats associated with rivers in mid-continental United States are important for waterbirds to rest and replenish energy reserves during migration. Kentucky Reservoir is the largest reservoir in the Tennessee River Valley (TRV), and extensive mudflat acreage is exposed during annual drawdowns. It has been proposed that timing of drawdowns will significantly affect waterbird use of TRV mudflats. Thus, I quantified influences of drawdown of Kentucky Reservoir on waterbird use, available food resources, and mudflat characteristics. From August - December 2006 and 2007, I conducted waterbird surveys twice weekly at 9 mudflats in Kentucky Reservoir. I quantified temporal and spatial changes at mudflat sites by sampling mudflat acreage weekly and vegetation, aquatic invertebrates, soil characteristics, and water depth twice monthly. Initial mudflat exposure occurred in early to mid-August; mean mudflat acreage was 35 ha.I recorded 26 species of shorebirds, 20 species of waterfowl, and 25 species of other waterbirds (e.g., herons, gulls) using mudflats in Kentucky Reservoir. Mean shorebird abundance, richness, and diversity were greatest during September, while mean shorebird density was greatest during August when mudflat acreage was lowest. Most long-distance migrant shorebirds of high conservation concern were recorded during August and September, whereas shorter-distance migratory shorebirds and waterfowl were most common October - December. Invertebrates were the most abundant food resource available to shorebirds and waterfowl (1.5 - 3.6 g m⁻²); Chironomidae was the most common taxa. Vegetation establishment and seed production decreased with decreasing mudflat elevation, which was related to duration of mudflat exposure.Soil moisture and compaction, water depth, and invertebrate density results revealed that optimal foraging conditions for shorebirds occurred within a 20-m band centered on the waterline. Shorebirds and waterfowl using mudflats spent the majority of their time feeding, while all other waterbirds spent most of their time resting. My results indicate that Kentucky Reservoir mudflats provide important foraging and resting habitat for a diverse assemblage of waterbirds. I recommend that mudflats in Kentucky Reservoir be exposed by 1 August (New Johnsonville gage height <108.81 m [357 ft] MSL) to provide habitat for rare long-distance migratory shorebirds and to facilitate vegetation establishment and seed production for waterfowl.

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