News: 2014 Interior Least Tern surveys complete
Story by Brannen Parrish
TULSA, Okla. - The Tulsa District U.S. Army Corps of Engineers in cooperation with the U.S. Fish and Wildlife Service, completed its annual survey of an endangered bird on Oklahoma and Texas rivers recently.
Tonya Dunn, a Tulsa District biologist, and Kevin Stubbs, a biologist from the U.S. Fish and Wildlife Service completed a count of Interior Least Tern fledglings on the Arkansas River, Aug. 13.
Dunn is in the process of tallying the final figures for the nesting season. Dunn has been counting the fledgling population on the Oklahoma portion of the Arkansas River and the Red River from July to August since 2006.
“We are still waiting for some numbers to come in but based upon our counts this was a really good year for the Interior Least Tern,” said Dunn. “On the Oklahoma portion of the Arkansas River, it looks like the number of fledglings will be higher than last year.”
In 2013, the Tulsa District reported 223 fledglings on its portion of the Arkansas River. Dunn estimates the final totals for the Arkansas River in Oklahoma to be above 360 fledglings for this season.
Along the Red River, Dunn estimates about 80 fledglings for the season, which is down from the 2013 total of 110.
A number of factors affect successful ILT nesting. Interior Least Terns prefer to nest in the center of sand bars and islands with little no vegetation. If the river levels are low when the terns are searching for nesting grounds what appears to be a safe nesting site may become hazardous if rainfall increases.
“If you get a flood event, what looked like an island will become a sand bar and destroy the nests,” said Stubbs. “If it’s early in the season they will re-nest but around late August, the majority will want to leave.”
Dunn said the Tulsa District works with various stakeholders to ensure river flows are at sufficient levels for the terns to find safe nesting grounds.
“Ideally you want to have big flows before the terns get here to scour the vegetation and so they don’t select an island that will be covered during a flood,” Dunn said. “Every year it’s a balancing act with hydropower, navigation, flood-risk management and recreation.”
When water levels are too low, mammals pose a greater risk.
“If coyotes or dogs know there is a food source on an island or sandbar, they will go after them,” Stubs said. “When people walk out onto the sandbars or ride their four wheelers and all-terrain vehicles on the sandbars, they run over the nests.”
After courting, female terns lay one to three eggs, which require about three weeks for incubation. Hatchlings require another three weeks to fledge but are poor hunters, and will rely on adults to provide small fish for up to three weeks after gaining their flight feathers.
The smallest of the tern species, ILTs migrate from as far south as Brazil to court and nest on islands and sand bars in U.S. waterways and tributaries from Montana to Texas and New Mexico to Louisiana. The birds were added to the list of endangered species in 1985.