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.