As I motored around the bend in the Mississippi River in my johnboat, I knew I was getting close. On the horizon, I detected a sliver of sand rising slightly above the water. I could see several terns flying over and diving headfirst into the river.
In another quarter mile, I had terns on all sides of me, and the sliver of sand was now a 30-acre island with more birds flying above it and landing on the sand. I approached the island, trimming the outboard, and the boat slid onto the shore. The terns paid little attention to me-until I stepped out of the boat and onto the dry sand.
Then the sand erupted with birds lifting off the ground and rising into the air. They protested my presence by mobbing in big circles around my head, screaming as they flew. It didn't matter to the terns that I was on the island to collect data that would shed light on their prospects for survival. I was getting the same chase-the-intruder-away treatment a coyote, a heron or an angler would receive if they were to venture onto the island.
The least terns were mobbing me because I had stepped onto one of their nesting colonies, and they were protecting their eggs and chicks. Their colonies are tight clusters of five to 100 nests on barren sand islands or sandy portions of wooded islands in the lower Mississippi River, south of Cape Girardeau. Depending upon the river level during June and July, least terns will nest upon six to 18 islands in a 210-mile stretch of the river from Cape Girardeau to the Missouri-Arkansas-Tennessee border.
Officials placed the interior least tern on the federal endangered species list in 1985. Since then the Conservation Department has been studying aspects of tern ecology. Our investigations have focused on determining how well least terns reproduce, what makes one island better than another for nesting and the birds' movements within the region.
Most recently, we looked at what places in the river held the most food for terns and how the availability of food influenced their success in raising chicks. All of this research is used by the Conservation Department to negotiate and work with the U.S. Army Corps of Engineers, which is responsible for the management of the Missouri and Mississippi rivers, to protect tern nesting habitat and encourage this species' recovery within the Midwest's system of big rivers.