The sora, sora rail or Carolina crake (Porzana carolina) is a small waterbird of the rail family Rallidae, sometimes also referred to as the sora rail or sora crake, that occurs throughout much of North America. The genus name Porzana is derived from Venetian terms for small rails, and the specific carolina refers to the Carolina Colony. The common name "Sora" is probably derived from a Native American language.
They migrate to the southern United States and northern South America. The sora is a very rare vagrant to western Europe, where it can be confused with spotted crake. However, the latter species always has spotting on the breast, a streaked crown stripe, and a different wing pattern.
Soras forage while walking or swimming. They are omnivores, eating seeds, insects and snails. Although soras are more often heard than seen, they are sometimes seen walking near open water. They are fairly common, despite a decrease in suitable habitat in recent times. The call is a slow whistled ker-whee, or a descending whinny.
Taxonomy The sora was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae. He placed it with the rails in the genus Rallus and coined the binomial name Rallus carolinus. Linnaeus based his description on the "little American water hen" that George Edwards had described and illustrated in 1750 from a specimen collected near the Hudson Bay. Linnaeus also cited Mark Catesby who had described the "soree" in his The Natural History of Carolina, Florida and the Bahama Islands. The sora is now placed in the genus Porzana that was erected in 1816 by the French ornithologist Louis-Pierre Vieillot. The genus name is derived from Venetian terms for small rails, the specific epithet refers to the Carolina Colony. The common name "Sora" is probably derived from a Native American language. The species in monotypic: no subspecies are recognised.
Description Adult soras are Sora (Porzana carolina) European birds online guide. Avibirds.com. Retrieved on 5 January 2013. long, with dark-marked brown upperparts, a blue-grey face and underparts, and black and white barring on the flanks. They have a short thick yellow bill, with black markings on the face at the base of the bill and on the throat. Sexes are similar, but young soras lack the black facial markings and have a whitish face and buff breast. They weigh about and have a wingspan of 35–40 cm. Soras have two common calls: a loud, squeaking "whinny" that decelerates and descends in pitch, often used to advertise territories; and a softer, ascending "ker-wee" or "sor-ah".Cornell Lab of Ornithology. (2022). "Sora: Sounds". In: All about birds: Bird guide. Ithaca, NY: Cornell University, Cornell Lab of Ornithology The latter call is sometimes presented as a possible origin for the species' common name.
Distribution and habitat The sora is common across North America, naturally occurring in 49 US states (the exception being Hawaii), all 10 Canadian provinces and two Canadian territories. Outside of the US and Canada, the species is found throughout Central America, the Caribbean, and northern South America. The species has been recorded as a vagrant in Iceland, Great Britain, Portugal, and at Lake Titicaca.
Soras breed from Nova Scotia northwest to southern Yukon and Northwest Territories, south to California, Arizona, and New Mexico and northeast to Pennsylvania and New England. Sora wintering grounds include the Caribbean, northern portions of South America, including Ecuador, Colombia, and Venezuela, north through Central America and Mexico to southern California in the West and coastal regions of the Southeast. From southern Kansas south to northern and eastern Texas and east through the inland areas of the southeastern United States, soras are typically only observed during migration in the spring and fall. In a few areas of the western United States, including central California and areas of Arizona and New Mexico, soras may occur year-round.Cornell Lab of Ornithology. (2003). "Sora". In: All about birds: Bird guide. Ithaca, NY: Cornell University, Cornell Lab of Ornithology
The size of an individual sora's home range varies. Sora brood-rearing home ranges in northwestern Iowa averaged . In Arizona, sora home range size varied from in the early breeding season to over in the postbreeding season. These seasonal differences in sora home range size were not significant (p>0.05).
Densities vary from to 12 soras/acre in Colorado to 0.47 pair/ha in Indiana. An average of 1.3 soras/ha responded to calls across sites in Colorado. A similar density of soras was found in southeastern Wisconsin. In Iowa, average density over two years and several marsh habitats was 1.3 pairs/ha. Landscape factors, such as marsh area, habitat edges within marshes, and the number of marshes in a region may influence soras.
Although soras occur in marshes of all sizes, they may occur at higher densities in intermediate-sized marshes. Soras were significantly (p≤0.01) positively related with total wetland area and perimeter area of surface water in east and central Maine and were significantly (p<0.05) positively related to area of wetlands in Saskatchewan. In Maine, soras used 10% of wetlands, 40% to 50% of wetlands from in size, and 20% of wetlands larger than . In western New York, soras were significantly (p=0.007) more abundant in marshes from in size than in smaller (< ) or larger () marshes. In addition, sora nests were detected more often in the marshes.
Soras are commonly reported in plant communities dominated by cattails (Typha spp.),Lor, Socheata Krystyne. 2000. Population status and breeding ecology of marsh birds in western New York. Ithaca, NY: Cornell University, Department of Natural Resources. Thesis sedges (Carex spp.), bulrushes (Scirpus spp.), smartweeds (Polygonum spp.), rushes (Juncus spp.), rice cutgrass (Leersia oryzoides), and barnyard grasses (Echinochloa spp.).Rundle, William Dean. (1980). Management, habitat selection, and feeding ecology of migrant rails and shorebirds. Columbia, MO: University of Missouri. Thesis
Soras also seem to prefer edge habitats. Breeding sora density was significantly (p<0.001) correlated (r=0.62) with the perimeter:area ratio of northwestern Iowa marshes. The distance from the center of sora territories to a habitat edge was also significantly (p<0.005) less than from the center of Virginia rail territories. In Arizona, habitat edges were closer to sora heavy use areas than random sites.
Wetland dynamics at a large scale can affect soras. Indices of sora population at three "levels of response" were significantly (p<0.01) correlated (r≥0.70) with the number of ponds present in the prairie pothole region of North Dakota in May.
Outside of wetlands, soras are most often reported in cultivated areas during migration or in the postbreeding period. For instance, a sora was observed from marshland in a cultivated field in Iowa in the middle of August. A male sora was observed less than from a large wetland in a soybean (Glycine max) field in northwestern Iowa during the postbreeding period. From early June to mid-July, soras were observed on farms in Saskatchewan sown mainly with wheat (Triticum aestivum).
Soras have also been reported in flooded wooded areas.Gibbs, James P.; Longcore, Jerry G.; McAuley, Daniel G.; Ringelman, James K. (1991). Use of wetland habitats by selected non-game water birds in Maine. Fish and Wildlife Research No. 9. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service In western New York, soras occurred during the breeding season on a study site where 26% of the area was categorized as "flooded timber," and 5% was classed as "scrub/shrub marsh". In eastern and central Maine, an average of 2.1 soras was observed in wooded swamps per 100 hours of observation during the breeding season. On a nonbreeding (August–April) site in southwestern Arizona, soras were found to use a "mixed shrub community" more than expected based on its availability. Soras were observed at low abundances on a site with douglas-fir (Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa), and trembling aspen (Populus tremuloides) in British Columbia.Morgan, K. H.; Wetmore, S. P.; Smith, G. E. J.; Keller, R. A. (1989). Relationships between logging methods, habitat structure, and bird communities of the dry interior Douglas-fir, ponderosa pine forests of British Columbia. Technical Report Series No. 71. Delta, BC: Canadian Wildlife Service, Pacific and Yukon Region
Soras use areas with a wide range of water depths. They are often observed in water less than deep, although the average water depth of sora heavy-use areas in Arizona was . In northwestern Iowa, average water depth in sora territories was , which was significantly (p<0.025) more shallow than water depths at random locations in the marsh. Sora nesting sites occurred in shallower water than random sites in western New York. Average water depths reported at nest sites range from for 4 sora nests in Colorado to nearly for sora nests in western New York. In areas of deep water, soras typically wade on mats of floating vegetation.
Water level fluctuations may result in nest abandonment. For example, at a site in Colorado where water level increased more than , a sora nest with 7 eggs was abandoned. In Alberta, soras nested in more vegetation types during a drought year, most likely due to substantially reduced water levels in the vegetation used the previous year.
Soras use areas with shallower water in fall than in spring.Reid, Frederic Arthur. (1989). Differential habitat use by waterbirds in a managed wetland complex. Columbia, MO: University of Missouri. Dissertation. Soras typically avoid open water. There is a significant (p≤0.05) negative relationship between area of open water and sora use of wetlands in Maine and sora relative abundance in Saskatchewan. In western New York, sora nesting sites had a lower percentage of open water than random sites, and in Arizona soras used open water areas less than their availability.
Sora nesting sites had larger percentage of emergent vegetation than random sites in marshes of western New York. Sora numbers in wetlands of northeastern North Dakota were significantly (p<0.05) positively correlated (r=0.45) with hectares of live emergent vegetation. In east and central Maine, wetlands used by soras had significantly (p=0.01) greater area of emergent vegetation than unused wetlands.
Density of emergent vegetation in sora habitat varies. Reported density of emergent vegetation ranges from an average of 121.9 stems/m2 in sora territories in northwestern Iowa to 333 stems/m2 on sites in northeastern Missouri used during fall migration. In western New York, cover was greater than 70% at 95% of sora nests. In addition, nesting sites had more horizontal cover at 20 inches (0.5 m) above water level than random sites. However, average stem density on sora territories was not significantly (p>0.05) different from random sites in northwestern Iowa.
Height of emergent vegetation in sora habitat also varies. It ranged from in the spring after a winter disturbance in northwestern Iowa to in areas heavily used by soras in Arizona. In marshes of western New York, average vegetation height at sora nesting sites was shorter than at random locations. However, the average height of emergent vegetation in sora territories in northeastern Iowa was not significantly (p>0.05) different from the height of vegetation in random plots.
In Arizona, both cover and height of vegetation used by soras varied with seasons. Conway suggested the differences likely reflected the varied diet of the sora. The availability of habitat in different seasons is another possible source of seasonal differences in sora habitat.