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King Rails

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Published on: May. 2, 2001

Last revision: Nov. 9, 2010

One morning last June, I visited a small marsh within the Cape Girardeau city limits. I stepped out of the car and walked a few steps to the edge of the marsh. My pulse quickened when I heard a sharp, "kek-kek-kek-kek" close by. I couldn't believe my good fortune to hear the rare call of a male king rail. I had heard this mating call in the marshes of Florida, where king rails are common in some areas, but in Missouri, it's a rare treat.

A hundred years ago, the song of the king rail was probably an integral part of Missouri's marsh music. In 1906, for example, Otto Widmann reported that king rails were "a fairly common summer resident in the marshes along the large rivers." In 1919, Harry Harris wrote that king rails were not an uncommon migrant and a rare summer resident in the Kansas City area.

Sadly, this is not the case today. The bird I heard last summer was one of only a handful I have seen or heard in Missouri in more than 20 years of observing birds. Other observers claim it was not unusual to hear or see king rails in marshes in the Bootheel as late as the 1950s. Today the species is found only occasionally at a few state conservation areas and national wildlife refuges. In fact, much of what we know about the biology of the king rail in Missouri came from a study conducted by biologist Fritz Reid, who worked at Ted Shanks Conservation Area in the 1980s.

In addition to the king rail, the group of North American rails includes the blackbird-sized black rail and the duck-like American coot. The true rails live in marshes, are secretive and are usually heard, not seen. In Missouri, these include black rails (very rarely), yellow rails (rare migrants), soras (very common migrants), Virginia rails (uncommon migrants) and king rails, our only regularly breeding species.

King rails are North America's largest true rails. They stand about 14 inches tall (about the height of a crow) and have a wing span of 16 inches. On average, they weigh just under a pound. Males are about 25 percent larger than females, and their bills are more brightly colored. The breast, neck, and head of king rails are reddish-brown or rust-colored, and their flanks sport alternating black and white bars. Their back is rusty-brown, with black areas in the centers of the feathers.

King rails have a slightly curved bill that measures about 2.5 inches long. Its color is dull tan to orange. A faint pale line occurs above the eye. The throat is dull white, and the top of the head is darker.

Like all rails, the bodies of king rails are flattened slightly from side to side, enabling them to slip through dense marsh grass without moving the vegetation. Like other members of the group, king rails have an expansive vocal repertoire of up to 15 described calls. One commonly heard call is a "clapper." Produced in unison by paired birds, this is a loud, accelerating series of "kak" or "jupe" sounds.

King rails breed in suitable wetlands from southeastern North Dakota to coastal Mexico, and east to Lake Erie and coastal southern New England. They do not occur in the Appalachians. They migrate south in autumn, mostly to coastal areas, but on rare occasions they'll stop as far north as southeastern Missouri.

In the Gulf Coast and along the south Atlantic Coast, king rails are sufficiently abundant to support limited hunting, but few hunters pursue them. Because of a loss of suitable wetlands used for nesting, a number of states prohibit hunting of king rails. In several inland states, they are considered endangered or threatened.

King rails breed in freshwater marshes and shrub swamps, and in tidal marshes with fresh or brackish water. The rail is generally associated with perennial plants, especially grasses, sedges and rushes. The water depth in ideal king rail habitat ranges from one-quarter inch to 10 inches. Most habitat for king rails in Missouri is in river bottoms, where shifting channels provide a variety of shallow wetlands.

Details of their habitat are poorly known. However. nests found in northeastern Missouri were at sites with damp soil or water up to nine inches deep. They feed in water less than six inches deep. Marshes with small hummocks and a variety of water depths should provide for most of a king rail's needs.

After spending the winter in southern coastal marshes, king rails may return to Missouri as early as late February, but most arrive by mid-May. Males typically begin calling to attract mates shortly after arrival.

After pairing, birds begin building nests. This activity usually lasts from mid-May until June, but some birds begin building nests as early as March. In southeastern Missouri, broods have been seen as early as April.

Females lay an average of about 11 eggs. Both sexes incubate the eggs, and incubation takes 21 to 23 days. The young are black balls of down after hatching, and the adults move them to brood platforms for rearing. Adults feed the young rails for a few days until they begin foraging on their own. Still, they may stay with the parents for more than a month. Little is known of the behavior of the birds at this time, but they may be observed occasionally on mud flats pursuing crayfish and other prey.

King rails eat a variety of small aquatic animals, and occasionally may consume berries, seeds and other plant foods. Missouri king rails eat mostly crayfish, which need aquatic habitats that are relatively unpolluted. A close relative of the king rail, the clapper rail of coastal salt marshes, shows similar preferences, eating mostly fiddler crabs.

Crayfish eat dead plant material, so they are most abundant in marshes with shallow, nutrient-rich waters. King rails appear to benefit from the natural drying of swales and sloughs in river bottoms, which concentrates prey and provide feeding sites in late summer. These sites provide sufficient food for raising young.

Like other North American rails, adult king rails molt their flight feathers after the young become independent. Once they grow new flight feathers, adults apparently leave Missouri for southern wintering areas. This occurs mostly in September, but they have been observed in Missouri through late October.

Because king rails are found more often by sound than by sight, population monitoring is based on listening. Rails respond vocally to taped calls. Such methods have been used in Missouri to determine where king rails live during the breeding season, but otherwise we know little about their populations and what causes them to vary. Healthy habitats usually support good populations, but good king rail habitat is rare nowadays in Missouri.

Today, king rails are considered endangered as a breeding species in Missouri. Their biggest threat is the loss of high-quality wetlands. Such wetlands are vulnerable to drainage and drought, as well as to deep flooding during heavy rainfall. Extending protection to shallow wetlands is essential for maintaining and increasing king rail populations in Missouri.

Wetland management for waterfowl can help increase king rail habitat, as has been demonstrated on some Conservation Department areas and on land belonging to waterfowl hunting clubs. However, the best flooding depths for waterfowl habitat are usually too deep to benefit king rails. Waterfowl management also employs frequent disturbance to produce high-energy plant foods for waterfowl, but the perennial emergent plants that king rails need take several years to mature. King rails also prefer variations in water depth that are sometimes not available on wetlands managed for waterfowl.

Perhaps the greatest threat to king rails in Missouri is loss of habitat. Only when we consider shallow wetlands and marshes as vital parts of the Missouri landscape will we be able to assure that this unique and interesting species will remain among us.

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