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Porzana carolinasora(Also: Sora rail)

By Robb Stavne

Geographic Range

Breeding range:

The sora (Porzana carolina) occupies much of temperate North America, ranging (in the west) as far north as the Northwest Territories, to the southern extremes of Arizona and New Mexico. The breeding range of P. carolina narrows in the east, occurring from Canada's Maritime provinces south to Maryland, USA.

Overwintering range:

As wetlands freeze in the breeding range of P. carolina, this species moves south to overwinter, occupying the southern United States from Arizona to Florida, and also throughout Mexico. In addition, many individuals migrate across the Gulf of Mexico and Caribbean Sea to overwinter in South America.

The coastline of California hosts P. carolina year round.

(Kaufman, 1996)

Habitat

The sora occupies a freshwater wetland habitat throughout its range; it also uses salt marshes while overwintering. The preferred habitat provides considerable cover for breeding soras, and consists mostly of freshwater wetlands with stands of cattail, sedges, and other tall wetland plants (Kaufman, 1996).

Physical Description

Sexually monomorphic. Length 20-30 cm (8-10"). In its breeding plumage, the sora's throat and face are black, with a short, yellowish bill. The breast and nape of neck are gray. The back is mottled brown and the belly displays black and white barring.

Immature and non-breeding plumages are plainer and buff colored with no black on throat or face. While in this plumage, the throat is white and the breast is light brown. The legs of P. carolina are yellowish green. The tail is usually held erect while walking and flying.

(Godfrey, 1986; Semenchuk, 1992)

The body of a sora is suited for the marshy habitat that they occupy. Lateral compression of the body offers easy travel through dense vegetation. The sora possesses short, round wings which offer seemingly weak, but highly maneuverable flight through tangled vegetation. Strong legs, with long slender toes on provide P. carolina with a strong walking and running ability amongst tangled wetland vegetation. Although this species prefers walking to flying, its long distance capabilities are evident in its migration, often crossing the Gulf of Mexico and the Caribean.

(Semenchuk, 1992; Kaufman, 1996)

Reproduction

Nests are woven into a shallow basket from dead emergent wetland vegetation, and attached to stalks of dense, live vegetation. Nests are generally placed over or adjacent to water, occasionally occurring in dry environments such as willows or grassy habitat near water's edge. (Godfrey, 1986).

The average clutch size ranges from 10-12 (sometimes 6-18) brown, spotted eggs, occasionally laid in two layers to accommodate such large numbers in a relatively small nest. Incubation by both parents lasts from 18-20 days, and is initiated with the laying of the first few eggs (Kaufman, 1996).

Young hatch asynchronously due to incremental stages of incubation. Precocial downy young may be cared for by one parent, as the other parent incubates remaining eggs. Young soras leave the nest shortly after hatching, and mainly forage themselves, having been taught by a parent (Salt and Salt, 1976). At 21-25 days young soras fledge and gain independence from their parents' care.

(Kaufman, 1996)

Behavior

The sora is commonly heard in many wetlands throughout its range, but is rarely seen. Similar to other rails, the sora is a secretive species, hiding in the dense vegetation of its wetland habitat. Startled individuals will sometimes flush to cover, flying with apparent weakness, but with high maneuverability. More common is for a sora to slip quietly into hiding, long before observation can occur. The sora calls frequently, whistling and whinnying its calls to other soras, as well as in response to other rails (pers. obs.).

Courtship and mating occur in early spring upon arrival at breeding ground. Monogamous pairs are generally solitary, and defend their territories against invasion through calls and active chasing. Courtship displays by both sexes involve ceremonial preening, and posturing.

(Kaufman, 1996)

Predators of the sora include herons, birds of prey and opportunitic mammalian predators. Young soras are especially vulnerable while foraging away from the protection of a parent.

(Salt and Salt, 1976)

Once breeding has been completed, soras become gregarious, gathering in large numbers as they fatten up for migration. Although the sora appears to be a weak flyer, during migration it makes lengthy flights, sometimes crossing the Gulf of Mexico and the Caribbean as it overwinters in South America. Migration patterns are mostly nocturnal.

(Kaufman, 1996)

Communication and Perception

Food Habits

Diet consists mainly of seeds, insects and snails. Seeds are obtained from sedges (Carex spp.), grasses (Calamagrostis spp., Bromus spp., Scoacloa spp., Poa spp., etc) or other wetland plants. Snails and insects are picked from ground surface, or by probing soft mud and vegetation with its bill.

(Kaufman, 1996)

Economic Importance for Humans: Positive

The sora is considered a game bird under the Migratory bird treaty act (U.S. Fish and Wildlife Service, 2000) and may be hunted for food.

Viewing a sora in its natural habitat is a well won prize for an avid birder's effort.

Conservation Status

Numbers have declined across the sora's range, coinciding with loss of wetland habitat, however the species is still abundant (Kaufman, 1996). The sora is an unprotected species, and is considered to be a migratory game bird (U. S. Fish and Wildlife Service, 2000), although it is not often hunted.

Other Comments

Observing a sora in its natural habitat is well worth the effort. Patient (and lucky) observers may catch a glimpse of this wetland inhabitant throughout the spring and early summer, at most any heavily vegetated wetland. Large, remote wetlands hosting dense stands of cattail (Typha latifolia) and other tall wetland plants often hold several pairs of breeding soras. Recorded playbacks (available at most birding stores) of soras or any other rail will virtually guarantee a response from a curious sora, although a whistled facsimile may also suffice (pers. obs.).

Contributors

Robb Stavne (author), University of Alberta, Cindy Paszkowski (editor), University of Alberta.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate

References

Godfrey, W. 1986. The birds of Canada. Ottawa: National Museums of Canada.

Kaufman, K. 1996. Lives of North American Birds. Boston: Houghton Mifflin Company.

Salt, W., J. Salt. 1976. The Birds of Alberta. Edmonton: Hurtig Publishers.

Semenchuk, G. 1992. The Atlas of Breeding Birds of Alberta. Edmonton: The Federation of Alberta Naturalists.

U.S. Fish and Wildlife Service, 2000. "Birds protected by the migratory bird treaty act: Game birds and hunted species" (On-line). Accessed November 20, 2000 at http://migratorybirds.fws.gov/intrnltr/mbta/gmebrd.html.

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