Identifier

etd-04052007-135919

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

Over the past 30 years, the king rail (Rallus elegans) has purportedly declined precipitously throughout its range, with the most severe declines seen in the migratory populations. King rails, however, are considered a game species in Louisiana and Texas, thus, it is important to determine what proportion of king rails wintering there are migratory. This is complicated because there is no reliable method to distinguish between king and clapper rails and few studies have attempted to capture wintering rails. The objectives of this study were to: 1) Determine the best method for capturing wintering rails; 2) Determine if morphometric measurements could be used to identify and sex king and clapper rails; 3) Determine the ratio of resident to migrant king rails in southern Louisiana and Texas using stable isotope analysis of feathers. I captured 523 rails, including 187 tentatively identified king rails, 68 tentatively identified clapper rails, 107 Virginia rails, 123 sora, and 38 yellow rails. The effectiveness of capture techniques were: 1) drop-door traps with drift fencing - 0.0063 rails per trap hour, 2) capturing by hand or net from an airboat at night - 2.13 rails per hour, and 3) capturing by hand or net from an ATV at night - 1.80 rails per hour. Discriminate analysis of morphometric measurements revealed that wing, tarsus and culmen measurements could be used to differentiate between king and clapper rails. Multiple stable isotope analysis of rail feathers, äD, ä13C, ä15N, and ä34S, showed distinct differences among winter collected king rails and known migrants, but did not show differences between the winter collected king rails and residents. This indicates that most, if not all, of the winter collected king rails were resident to Louisiana and Texas. A linear relationship was seen between äDf values and estimated äDp values at the collection locations (r2 = 0.42). The fractionation factor that resulted from this analysis could be used to determine an approximate breeding location for the winter collected rails, and also indicated that most, 99%, of the winter collected king rails were resident to Louisiana and Texas.

Date

2007

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Sammy King

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