Interior Least Tern Floating Habitat Project

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US Army Corps of Engineers
Rivers Project Office

Upper Mississippi River
River Mile 201-203
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Location: Ellis Bay is located in Pool 26 along the right bank of the Mississippi River at river miles 201 to 203, directly across the river from Alton, Illinois, immediately downstream of the Clark Bridge, and immediately upstream of the Melvin Price Locks and Dam. The project area is separated from the main channel of the Mississippi River by Ellis Island and US Highway 67.


The project area is managed directly by the U. S. Army Corps of Engineers, Rivers Project Office, within the Riverlands Migratory Bird Sanctuary. Management of the project area will be directed through the Environmental Stewardship Program for enhancement of habitat for species of federal interest and to enhance the recovery of migratory species. This is also done as part of compliance with the Endangered Species Act and USFWS Biological Opinion for the Operation and Maintenance of the Nine-Foot Navigation Channel on the Upper Mississippi River System for nesting habitat creation for the endangered interior Least Tern, Sterna antillarum.


Resource Problem: The loss and virtual elimination of sandbar habitat type in the lower downstream segments of hinge point navigation pools is evident. This habitat loss is substantially caused by the continued absence of the dynamic physical changes that take place within natural river processes that create this type of habitat over time. The loss of sandbar habitat is primarily due to the regulated hydrology of a hinge point navigation pool. During increased river flows, the flat water surface elevations at the pool areas adjacent to the navigation dams are first lowered as much as five to six feet, progressing to an “open river” flow condition with inclined water surface elevations. At this “open river” flow condition with inclined water surface elevations, a natural river hydrology begins to takes place, and water surface elevations begin rise proportionately with increased river flows. Not until surface waters again rise five to six feet in elevation, do the shorelines of the stable navigation pools become again inundated or experience sediment accretion. This time interval during increased river flows between stable flat navigation pools and open river conditions meeting the navigation pool shorelines historically had provided for both the natural accretion and formation of new sandbar islands and the natural accretion and denuding of the sandbar toes of natural river islands. This dynamic process for natural sandbar habitat creation has evidently been lost in the immediate pool areas above navigation dams.


Spring draw downs of the pool from the Melvin Price Locks & Dam provides abundant habitat for the Least Tern. This drawdown is only a temporary effect of managing the navigation pools. When the pool returns to its summer level, the sand bars are inundated and the Least Tern cannot complete their nesting cycle. Over the years, many options for increasing Least Tern habitat have been considered. It was decided that a permanent island would be build to provide nesting habitat for the Least Tern at the tip of Ellis Island within the Riverlands Migratory Bird Sanctuary. This is known as Ellis Island Least Tern Habitat Project and was completed in 2002. St. Louis Audubon Society was involved in this project and after its completion, monitored the island for Least Tern nesting activity during the first nesting season. Although several terns have been observed in the area, none have nested on the permanent island.


The established island is attached to Ellis Island through a low water access. This allows land based access for maintenance of the island. It is possible that since this access area is not always inundated, the sand bar does not meet the Least Tern criteria for nesting habitat.


Project Goals and Objectives: The project goal is to restore the sandbar habitat to this stretch of the Mississippi River. It is expected that this habitat will provide ideal nesting conditions for breeding Least Terns. This type of floating habitat will be used for sighting of future permanent habitat locations.


Project Features: The direct benefit from this project will be creation and protection of sandbar nesting habitat for the endangered Least Tern and other shorebirds. The uniqueness of this project also provides for demonstration and education opportunities since it is easily viewable from Riverlands Way.


The project consists of two floating pontoon barges anchored in Ellis Bay (no wake area), Mississippi River Mile 201.7. The two barges are lashed together for a combined 1,500 ft2 of temporary nesting habitat. These barges are topped with approximately 5” of a sand/gravel mix, to simulate a sandbar habitat. Timbers (6’x6’) are used to edge the barges, so the sand/gravel mix will stay on barges, but allow rain water to drain off. Conspecific attraction equipment (call boxes and decoys) are also used on the barges in an attempt to interest the birds in this particular site. There are a total of 20 decoys located on the barges; most of them are in pairs. The call box recordings run intermittently for 24hours. The main power source for the call boxes is a marine battery, which is connected to a solar panel to maintain a full charge. The call box will be stopped if and when the Least Tern eggs hatch.


Agency Stakeholders: U.S. Army Corps of Engineers is working with the Illinois Department of Natural Resources (IDNR) and Illinois Natural History Survey (IHNS) for this project. IDNR and INHS have provided technical expertise on barge placement, call box and decoy set-up, and may conduct future studies if successful breeding occurs.


Project Updates

2009 Breeding Season: The barges were pushed into place and anchored on April 30, 2009. The first reported sighting of least terns in the area and landing on the barge was May 14. On May 29, an intern with the National Great River Research and Education Center began daily monitoring of the island from shore. On June 19, it was confirmed that there was one nest on the island with three eggs. On July 7, an additional 11 nests were confirmed with two hatchlings in the first nest, bringing the total nests to 12 with a total of 30 eggs in all the combined nests. On July 24 and August 6, biologist from the Corps of Engineers, Illinois Department of Natural Resources, and Illinois Natural History Survey banded a total of 20 hatchlings. It was suspected that an additional 3 hatchlings had fledged before the crew could arrive to band the young terns.

2010 Breeding Season: Least terns first arrived on May 11th of 2010. Peak number of nests and eggs were observed on June 16th, 2010 with 21 nests containing 56 eggs. By July 6th, 2010, 19 chicks were hatched and ready to be banded. Predation by a great blue heron (Ardea herodias) on July 9th, 2010 caused the least terns to abandon the colony. No least terns were seen on or after July 12th, and all remaining nests and eggs were abandoned. In response to the predation by a great blue heron, five foot tall metal mesh wire fencing was placed around both barges and additional lattice covering to the remaining uncovered sections of the barges.

2011 Breeding Season: Due to a prolonged period of low water, the barges were placed in Ellis Bay later than expected. (We’ll have more updates as the season moves along.)

2012 Breeding Season: Barges were moved to new breeding season location to enhance monitoring capabilities and public viewing from the St. Louis Audubon Center. Barge monitoring and driving surveys were conducted for arriving least terns in April/May and continued throughout the summer. Least terns first arrived on May 22nd of 2012. Nesting on the barge was confirmed on June 11th when 5 nests, 15 eggs, and 10 adults were observed. On June 25, 10 nests, 16 eggs, 9 chicks, and 12 adults were observed. On July 9, 12 nests, 5 eggs, and 9 chicks were observed. On July 12, 24 flying least terns were observed. It is estimated that a minimum of 12 chicks successfully fledged this year. There was no evidence of predation this year and the fences appear to be working.



The US Army Corps of Engineers plans to continue the effort in the 2011 nesting season. We also plan to investigate site fidelity, behavioral response to other tern species, nest density rates, and least tern response to increased predator defenses. If you would like further information on the project please contact Benjamin McGuire, Wildlife Biologist with the U.S. Army Corps of Engineers, Rivers Project Office, 301 Riverlands Way, West Alton, MO 63386, (636) 899-2600.



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Figure 1. Approximate 2009 and 2010 barge placement shown by red box.
(In 2011 we're planning to move the barge closer to the Project Office)

For more information please contact:

Benjamin McGuire
Wildlife Biologist
Rivers Project Office
301 Riverlands Way
West Alton, MO 63386
Phone: 636.899.0096
Benjamin.M.McGuire@usace.army.mil

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