Ridgway's Rail Life History

Habitat

Ridgway's Rails live in saltmarsh swamps with extensive vegetation, which they use as refuges, especially at high tide. These birds live in low portions of coastal saltmarshes dominated by cordgrass and pickleweed, or in mangroves. The Yuma form of Ridgway's Rail lives inland, in the Salton Sea and in freshwater marshes along tributaries of the Colorado River. Back to top

Food

Ridgway's Rails are opportunistic and omnivorous, and their food selection reflects what’s available in their environment at any given time of year. They eat crustaceans such as crabs, crayfish, and shrimp; fiddler crabs are a favorite item if they can be found. Other food includes insects, snails, fish, bird eggs, slugs, vegetation, and seeds—the last two items are consumed more in the winter. Ridgway's Rails typically forage by slowly walking through dense reeds and other vegetation, or along edges between marshes and mudflats. They find prey by sight, and possibly by smell, usually grabbing food items from the surface or with shallow probing into the mud. Many prey are swallowed whole, and pellets of indigestible material (such as clam shells) are later regurgitated.Back to top

Nesting

Nest Placement

Nest site selection involves a compromise between higher sites with less cover—to avoid flooding—and lower-lying sites with tall grasses and better concealment from predators. The birds (usually the males) build their nests in clumps of vegetation or in shrubs, from just above ground level to about 4 feet off the ground.

Nest Description

Males do most of the nest building and may continue to add to the nest after the female has started incubating eggs. Nests are a bulky platforms of marsh vegetation and are tall and camouflaged to protect them from tidal flooding and keep them concealed. Nests may have domes to help keep them hidden, and ramps to enable entry and exit in habitats with high or fluctuating water levels. Nests are 7-12 inches in diameter, with an inside cup 4-8 inches across and 1-3 inches deep. Domes are 16-28 inches higher than the rim of the nest. Ramps can be 4-22 inches long, and up to 6 inches wide. The male may add material during periods of high water. Both sexes incubate the eggs—usually the female during the day, and male at night—and raise the young. Pairs may renest up to 5 times after the failure of previous nests. Adults may use a “broken wing” display to lead predators away from nests.

Nesting Facts

Behavior

Ridgway's Rails live most of their lives concealed in dense vegetation, though they occasionally climb into tall vegetation to investigate calls of other animals or unfamiliar sounds. They rarely fly, instead walking often in an irregular path with neck outstretched, and tail erect, or jerking up and down if agitated. Birds may run in response to a threat, holding tail and head straight out and body horizontal. These birds spend much of their time foraging for prey by picking items from the ground, or by probing into the mud. Ridgway's Rail are territorial during nesting season but may form loose aggregations of nests as habitat quality and high water levels dictate. Birds respond to alarm calls of other species. They swim well, and may dive if threatened. Ridgway's Rail are monogamous during the breeding season, and pairs work together to raise young.Back to top

Conservation

All U.S. populations of Ridgway's Rail are federally protected as Endangered due to habitat loss, pollutants, urbanization, and exotic predators. The species is listed as Near Threatened on the IUCN Red List. Partners in Flight estimates the global breeding population at 15,000 individuals and rates the species a 17 out of 20 on their Continental Concern Score. Ridgway's Rails are on the Partners in Flight Red Watch List for species of highest conservation concern.

Habitat loss due to development and degradation is a leading cause of population declines. Land development can alter important aspects of habitat such as vegetation, water levels, and salinity. The population in California's San Francisco Bay has been severely compromised as up to 90% of the bay’s original 285 square miles of marsh has been filled, destroyed, or diked, and much of the remainder is degraded. Because they are a wetland species, nearly all populations live in habitats with contaminants. Invasive predators such as Norway rats, red foxes, dogs, and cats are also threatening this species. Other predators include raccoons, mink, coyotes, opossums, crows, and gulls. Small populations have caused inbreeding in some areas which may contribute to low fertility and poor breeding success.

Credits

Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

Eddleman, W. R. and C. J. Conway. (2018). Ridgway's Rail (Rallus obsoletus), version 2.1. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.

Lutmerding, J. A., and A. S. Love (2017). Longevity records of North American birds. Version 2017.1. Patuxent Wildlife Research Center, Bird Banding Laboratory, Laurel, MD, USA.

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

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, NY, USA.

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