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Towhead of Island #18 and Least Terns

Towhead of Island #18

Towhead of Island #18

Wildlife officials in the State of Kentucky are warning residents riding off-road vehicles to stay away from places like the Towhead of Island #18 in the Ohio and Mississippi Rivers where least terns nest during the summer.

“Island No. 18: Lies close to the right shore. Opposite the head of No. 18 is a bar, may go on either side of it. If you get between the island and the bar, keep close to the bar for fear of being drawn on snags and sawyers on the side of the island.”–Zadok Cramer, 1814

The towhead of island # 18 was once a major navigation problem; now it’s an important habitat for least terns.

Zadok Cramer described the difficulties of getting around Island #18 in 1814. The difficulties had not changed sixty years later. In 1874 steamboats had to negotiate their way through snags to get around Island #18, one of three divided channels north of Cottonwood Point, Missouri. The left channel went around the island, the middle channel between the island and its towhead, and the right channel, the navigation channel, through what is now Everett Lake. Sometimes, the channel was eight feet deep, sometimes not. Zadok Cramer had Island #19 lying to the east of #18, but Samuel Cumings, writing in 1829, figured it had disappeared during the New Madrid earthquakes. Major Charles R. Suter, who surveyed the Mississippi from Cairo to New Orleans in 1874, noted that dike fields would be needed to solve the navigation problems in this stretch of the river.

The combination of a dike field on the right bank at Linwood Bend up stream and its revetment to protect the opposite bank, a second dike field on the right bank of the towhead of Island #18 and its revetment on the opposite bank created a reliable channel. Island #18 attached itself to the Missouri bank. The Corps of Engineers built a closing dam between the towhead and the left bank, creating Everett Lake. A new sand bar formed over the dike field, causing great excitement among birders. At the beginning of twenty-first century, it harbored an increasing population of least terns.

Least Tern

Least Tern

In 1985 the Memphis District of the Corps of Engineers began making annual surveys of the least terns that nested on Lower Mississippi River sand bars between Cairo and Baton Rouge. To begin with they surveyed by towboat, by small boat, and by airplane, but discontinued the towboat and aerial surveys when they realized that the most accurate counts came after cruising by the river’s sandbars in small boats. Kenneth Jones, an associate professor of biology at Dyersburg Community College in Tennessee led the surveys after 1997.

When Jones and his helpers surveyed the Island #18 sandbar in 2001, they found it “large, flat, and gently sloping,” scattered with willow and cottonwood seedlings. The nearest tall trees were three-quarters mile away. Within five hundred feet of the river, they found 150 adult least terns, nests containing as many as three eggs, and chicks, between one and seven days old. There were no foot-prints, human or otherwise, predators who might disturb the terns’ privacy. Fingerling sunfish and shad, food for terns, swam in the side channel.

Over the next three years the size of the island increased, the size of the trees increased, the population of the terns increased to 202 adults in 2002, 225 in 2003, 450 in 2004.

In 2004 Jones and his colleagues found sixty-nine nesting colonies harboring 11,239 least terns. They found eggs and chicks in fifty-eight of the colonies. In eleven they found adult terns exhibiting nesting behavior, wetting their breast feathers, carrying fish, or chasing away intruders. The Nebraska Point Dikes, Kangaroo Point Dikes, Island #84, and opposite Warnicott Landing Dikes, hosted six hundred or more terns.

Jones began his 2004 survey in July when the river had fallen below twelve feet on the Memphis gage. Once he or his colleagues spotted a site, they would head the boat to the greatest concentration of birds, get as close as they could in shallow water, cut the engine, drift, and start their count using binoculars. One surveyor counted the birds along the waterline, the other the birds in the air. That done, they beached their boat and fanned out across the colony, looking for nesting activity, the presence of eggs, or better yet, chicks. Should the terns harass them, they accepted that as nesting activity. They allowed themselves fifteen minutes, tops.

The population dropped to 270 in 2005, so did the size of the sandbar.[i]

[i] Cramer, Zadok, The Navigator, Ann Arbor: University Microfilms, Inc., 1966, 169; Bragg, Marian, Historic Names and Places on the Lower Mississippi River, Vicksburg: Mississippi River Commission,  1977, 46; Lower Mississippi Conservation Initiative, Tennessee Wildlife Resources Agency, Meeting Notes, November 6, 2001, Jackson, Tennessee, http://www.lmrcc.org/TNmtpdf.pdf; Jones, Kenneth H., “Population Survey of the Interier Least Tern on the Mississippi River from Cape Girardeau, Missouri to Baton Rouge, Louisiana,” U.S. Army Corps of Engineers, Memphis District, 2004, http://www.island63.com/2004leasttern.cfm; Tennessee Wildlife Resources Agency, “Mississippi River, Least Tern Breeding Colony–Island No. 18 Towhead Dikes, Dyer County, Tennessee,” http://www.tnbirds.org/IBA/SitePages/MississippiRiverIslandNo18TD.htm.


One Response

  1. Great site, I now have you bookmarked to come back again.

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