Construction at River Region Medical Center on U.S. 61 North(The Vicksburg Post/MELANIE DUNCAN)

[05/04/01] The Vicksburg National Military Park gets thousands of visitors each year, but Dan Twedt isn’t interested in those who come in motor vehicles. His main interest is in the visitors that fly and flit among the trees covering the park’s hills and hollows.

Twedt is a wildlife biologist with the U.S. Department of the Interior Geologic Survey and is working on a pilot survey of birds that use the park during their migration north.

In order to identify the birds and determine their condition, Twedt and his assistants must first capture them. To do that, yards and yards of mist net have been strung among the trees at four locations in the park.

“We started in late March or early April and we will end up later this month,” Twedt said.

The main purpose of the study will be an attempt to determine if birds returning to the United States from their wintering grounds use upland hardwood or bottomland hardwood areas as their main traveling routes. Bottomland hardwoods are woodlands such as those along Mississippi 465 that grow in areas subject to flooding. Upland hardwoods are found in the hills around Vicksburg.

The park survey sites are considered upland hardwoods, but Twedt has other capture sites in nearby bottomland forests.

“We know that when the birds hit the Gulf Coast, they use the bottomland hardwoods,” he said.

One of the main questions he’d like to settle is whether the birds continue to use the bottomlands, which are less broken up, or if they switch to the uplands, which are more fragmented.

In addition to the sites of the pilot program, Twedt said the USGS also has sites for Monitoring Avian Productivity and Survival projects located all over the United States.

He said the park sites normally capture 30 to 40 individual birds during a morning’s use and these birds normally represent 12 to 18 different species.

Since the 40-foot-long by 8-foot-high nets are set relatively low, Twedt catches mostly birds that live and fly close to the ground and those that live in the middle levels of the trees and brush.

Some of the more common species caught are hooded and Kentucky warblers and white-eyed vireo. One of the more unusual birds captured was a Lincoln’s sparrow.

The Lincoln’s sparrow is similar to the more common song sparrow. Its summer range is generally in Canada and small portions of a couple of northern tier states. Its wintering range takes in far western Mississippi and the Gulf Coast counties. However, in colder months, the largest portion of the bird’s range is west of Mississippi.

Bob Irish, one of the VNMP rangers who is helping Twedt, said the USGS will share the results of the work with the National Park Service.

The NPS is compiling a nationwide survey of the natural resources within each of its parks. The purpose, he said, is so the park service will know the types of resources within each park, and whether those resources are improving or declining.

In addition to Twedt’s study, Dr. Ed Kaiser from Mississippi State University is surveying amphibians compiling a list of the snakes, turtles, frogs, toads, lizards and salamanders that call the park home.

The Nature Conservancy surveyed plant life in the park several years ago.