TULSA, Oklahoma - When the river trails and walking paths finally open around the River Spirit complex you’ll have closer access to the Arkansas River.

There you’ll notice some odd rock formations in the middle of the river, and wonder who put them there and what they are for.

Several weeks ago, Osage SkyNews 6 HD came back with some pictures of odd rock formations in the river, leaving us wondering what they were.

Well, turns out the rocks are in the river to help the Least Terns.

Gaylon Pinc said, "They are the smallest of the tern population, therefore the name, Least Tern."

And, no offense to the little guys, but they are not always very smart about where they set up housekeeping.

"The terns don't want vegetation; they won't go to an island that is vegetated," Pinc said.

If their island is not surrounded by water they’re susceptible to predators, so, the Program Management Group, PMG, has been tasked with providing some help for the terns.

They went to a plan from the Biosystems and Agricultural Engineering Department at OSU, and that's where the formations came from.

Water flows over and around the chevron formations, sand in the water is deposited behind and in front of the rocks forming sand bars; high enough above the water line when the river is full, yet surrounded by water when the water is low - perfectly protected nesting areas.

And more are coming - from River Spirit, all the way back to The Gathering Place.