King Rail Life History

Habitat

Habitat Marshes

King Rails breed in both freshwater marshes and brackish marshes (especially ones with very low salinity). Similar to Least Bitterns, they are most numerous in shallow marshes that contain patches of deeper, open water. Rice fields, both planted and harvested, also attract King Rails year-round, including during the nesting season. King Rails are very particular about water levels, and their foraging areas and territories shift with changing water levels. During drought years, areas of marsh that are normally too deep for foraging and nesting might be utilized, whereas during wet years, they may be able to use higher parts of marsh that are normally too dry to use. They most often occur in vegetation that is tall enough to provide some cover but also near enough to pools and shallow edges for foraging. They avoid areas with woody vegetation. Specific marsh plants associated with King Rail, both for nesting and wintering, include cattails, sturdy bulrush, maidencane, bulltongue arrowhead, Jamaica swamp sawgrass, giant cutgrass, black needlerush, and introduced Phragmites.

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Food

Food Aquatic invertebrates

King Rails eat mostly crayfish, fiddler crabs, and other small crustaceans. They also take small clams, fish, frogs, small snakes, mice, shrews, katydids, dragonflies, grasshoppers, beetles, crickets, aquatic insects, fruit, acorns, and seeds of aquatic plants, including rice. Typically, King Rails wade through shallow waters, hunting prey visually, and seize items quickly with the bill. Larger prey, such as large crayfish, are dismembered before being eaten, but most items are swallowed whole. They hunt more in the early morning and late afternoon than during the heat of the day, but in cooler weather may be active throughout the day. King Rails sometimes move into upland and shrubby parts of marshes to hunt prey such as grasshoppers.

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Nesting

Nest Placement

Nest Ground

Males apparently select the nest site and do most of the nest construction. They also sometimes build a sample nest that is not used, as well as several nests that serve as shelters for the chicks once they hatch. Nests are set inside marsh vegetation in shallow water, seldom in upland portions of marshes.

Nest Description

Nests are simple round platforms elevated above the water, made of marsh grasses or rice, whatever vegetation is near the nest site. The base of most nests is made of wet decaying vegetation; the platform (or cup) is made of dead dry grasses, sedges, or rushes. The male often bends adjacent living vegetation over the nest to form a shelter and sometimes builds a ramp down to the water level, normally less than 12 inches below the top of the nest (at high tide). Nests are about 6.5 inches tall (the canopy extends about a foot above the nest rim), 11 inches across, with a central depression 0.6 inches deep.

Nesting Facts
Clutch Size:10-12 eggs
Number of Broods:1-2 broods
Egg Length:1.5-1.3 in (3.85-3.4 cm)
Egg Width:1.1-1.3 in (2.8-3.2 cm)
Incubation Period:21-23 days
Egg Description:

Pale buff with a few irregular brown spots.

Condition at Hatching:

Covered with black down, leave nest within one day. Fed by parents.

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Behavior

Behavior Probing

Males court females by strutting and cocking the tail quickly to show their white undertail coverts. When the female nears, the male gives chase, with tail up, neck outstretched, head angled upward, and bill open—looking like a wild pose from an Audubon painting. Males also bring prey to females when courting. They drive rival males from their territory, or at least away from the nesting area, and also chase other rail species. King Rails forage within a home range that varies from about 11 acres to 68 acres. Not all of this area is defended, but there is little overlap between pairs’ ranges when water levels are stable. Both parents care for the young, which take almost 2 months to become independent. Northern populations of King Rails are migratory and can turn up in almost any setting, including saltmarshes normally occupied only by Clapper Rails. King Rails regularly hybridize with Clapper Rails in brackish environments.

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Conservation

Conservation Declining

King Rail populations have declined in all areas surveyed in North America, overall by an estimated 4.5% per year since 1966 according to the North American Breeding Bird Survey, indicating a cumulative decline of 90% over that period. Partners in Flight estimates the global population at 70,000 birds, rates the species a 15 out of 20 on the Continental Concern Score, and includes it on the Yellow Watch List for declining populations. The IUCN classifies King Rail as a “Near Threatened” species. Long-term declines in populations are mostly related to the massive loss of wetlands across North America. Hunters take about 15,000 rails (of all species) per year in the United States, according to the U.S. Fish and Wildlife Service. King Rails also get hit by cars and collide with buildings and other structures (both during the nesting season and during nocturnal migration). Pesticide, lead poisoning, and other water-quality issues affect this aquatic bird. Changes in rice-farming techniques have also rendered large areas of Louisiana and Arkansas that formerly supported sizable populations of King Rails uninhabitable. Global climate change is forecast to produce more frequent and stronger tropical storms, which kill large numbers of rails, including King Rails. Rising sea levels will lead to more saltwater intrusion into aquifers throughout the Southeast, which will alter both natural marsh communities and rice farms.

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Credits

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Meanley, B. (1969a). Natural history of the King Rail. N. Am. Fauna 67.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Pickens, Bradley A. and Brooke Meanley. (2018). King Rail (Rallus elegans), version 2.1. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Raftovich, R. V., S. C. Chandler, and K. K. Fleming. (2018). Migratory bird hunting activity and harvest during the 2016-17 and 2017-18 hunting seasons. U.S. Fish and Wildlife Service, Laurel, MD, USA.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.

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