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Rostrhamus sociabilis plumbeus

Ridgway, 1874

Snail Kite

T2T2 (G5T2) Found in 2 roadless areas NatureServe Explorer →
T2T2Global Rank
Everglade snail kite (Rostrhamus sociabilis plumbeus). Photo by U.S. Fish & Wildlife Service, Public Domain (U.S. Government Work), via ECOS.
U.S. Fish & Wildlife Service, https://www.usa.gov/government-works
Identity
Unique IDELEMENT_GLOBAL.2.102826
Element CodeABNKC07011
Record TypeSPECIES
ClassificationSubspecies
Classification StatusStandard
Name CategoryVertebrate Animal
CITESAppendix II
Endemicendemic to a single state or province
KingdomAnimalia
PhylumCraniata
ClassAves
OrderAccipitriformes
FamilyAccipitridae
GenusRostrhamus
Concept Reference
American Ornithologists' Union (AOU). 1957. The AOU check-list of North American birds, 5th ed. Port City Press, Inc., Baltimore, MD. 691 pp.
Taxonomic Comments
Three subspecies, R. s. plumbeus, R. s. major, and R. s. sociabilis, are recognized by Birds of the World (Reichert et al. 2020), but other authorities have considered Snail Kite monotypic. The three subspecies (e.g., Amadon 1975, Dickinson and Remsen 2013) are diagnosed on aspects of body size (Baird et al. 1874, Friedmann 1933, 1950, Nelson and Goldman 1933), but size overlaps too extensively for populations to be diagnosable at the standard 75% rule needed for valid subspecies (Reichert et al. 2020). Retained here due to U. S. Fish and Wildlife endangered status (see USFWS 2023).
Conservation Status
Review Date2010-03-29
Change Date2005-10-07
Edition Date1994-02-24
Edition AuthorsJackson, D. R., and C. C. NeSmith
Range Extent250-20,000 square km (about 100-8000 square miles)
Number of Occurrences6 - 20
Rank Reasons
Small range in Florida and Cuba and the Isle of Pines; very low total numbers; population and range have declined dramatically since river channelization and drainage of wetlands began in 19th and 20th centuries; reproductive output is tied closely to environmental fluctuations; human population growth and increasing demands for water threaten this kite's future.
Range Extent Comments
Restricted to Florida, U.S., Cuba and the Isle of Pines. Formerly occurred in freshwater marshes throughout peninsular Florida. Now restricted to St. Johns River headwaters; southwestern Lake Okeechobee; small areas in Broward, Dade, and Palm Beach counties; parts of Everglades National Park, Loxahatchee National Wildlife Refuge, and Big Cypress National Preserve. Present distribution of the kite in Cuba is not well known.
Occurrences Comments
Occurrences may change from year to year, dependent upon water levels. Reproductively gregarious, hence only a few breeding colonies. Drought-related occurrences may be sporadic but are critical to the survival of the kite during drought conditions.
Threat Impact Comments
Habitat destruction, principally via wetland drainage and conversion for agriculture, is the major threat. Agricultural runoff has caused pollution and eutrophication of much of habitat below Lake Okeechobee. Introduction of exotic plants (e.g., water hyacinth, water lettuce, torpedo grass, and hydrilla) prevents feeding. Illegal shooting by humans, particularly during waterfowl hunting season.
Ecology & Habitat

Description

Adult male is black with white uppertail and undertail coverts, white tail with broad dark band and pale terminal band, orange-red legs, and reddish eyes and facial skin; adult female is dark brown and has patches of white on the forehead and throat, otherwise similar to male; immatures resemble adult females but have boldly streaked head and underparts and paler legs; all have a long hooked bill; averages 43 cm long and 117 cm in wingspan (NGS 1983).

Diagnostic Characteristics

Differs from subspecies SOCIABILIS of Central and South America primarily by having longer wings; smaller than Mexican subspecies MAJOR (Friedmann 1950).

Habitat

Florida: large, open freshwater marshes and lakes with shallow (< 4 ft) open waters; open water areas without emergent vegetation are required for foraging; nests usually 1-5 m above water in low tree or shrub (commonly willow, wax myrtle, pond apple, or cattails), also occasionally sawgrass, maidencane (especially during low water) used for support (Palmer 1988); usually builds (mainly male) a new nest for each nesting attempt, though may build over old nest or in same location as old nest (Johnsgard 1990).

Ecology

Tends to be gregarious, especially nonbreeders. Local movements may include long daily flights between communal roost and daily feeding or nesting area.

Reproduction

Main nesting period is January-August (eggs laid mainly February-April). Clutch size is usually 2-3 in Florida. Incubation, by both sexes, lasts 26-30 days. Young are tended by both sexes 3-6 weeks, then one adult deserts (and may renest) unless snails are scarce; sustained flight occurs at about 6-7 weeks; fed by parent until age 9-11 weeks. Young fledge at 23-28 days according to Matthews and Moseley (1990). Nestling period in Florida averaged 29 days (see Johnsgard 1990). First breeds at 1-2 years (reaches breeding age at 10 months according to Matthews and Moseley 1990). Florida: poor nesting success (0-41% in the late 1970s-early 1980s) but population has increased in recent years due to multiple nesting attempts and high survival rates of free-flying individuals (annual adult survivorship probably is over 90%) (Snyder and Beissinger 1989). Reproductive output is tied closely to environmental fluctuations (Nichols et al. 1980, Snyder et al. 1989). Nest failures usually are due to drought, structural failure, or predation (e.g., by rat snake). Loose colonial nesting of a few pairs is common; typically defends only the immediate vicinity of the nest (Johnsgard 1990).
Palustrine Habitats
HERBACEOUS WETLANDRiparian
Other Nations (1)
United StatesN2
ProvinceRankNative
FloridaSNRYes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquaculture———
2.1 - Annual & perennial non-timber crops———
5 - Biological resource use———
5.1 - Hunting & collecting terrestrial animals———
7 - Natural system modifications———
7.2 - Dams & water management/use———
8 - Invasive & other problematic species, genes & diseases———
8.1 - Invasive non-native/alien species/diseases———
9 - Pollution———
9.3 - Agricultural & forestry effluents———

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Roadless Areas (2)
Florida (2)
AreaForestAcres
Alexander Springs CreekOcala National Forest2,954
Farles PrairieOcala National Forest1,901
References (33)
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  2. American Ornithologists' Union (AOU). 1957. The AOU check-list of North American birds, 5th ed. Port City Press, Inc., Baltimore, MD. 691 pp.
  3. American Ornithologists' Union (AOU). 1983. Check-list of North American Birds, 6th edition. Allen Press, Inc., Lawrence, Kansas. 877 pp.
  4. Beissinger, S. R. 1983. Hunting behavior, prey selection, and energetics of snail kites in Guyana: consumer choice by a specialist. Auk 100:84-92.
  5. Beissinger, S. R. 1990a. Alternative foods of a diet specialist, the snail kite. Auk 107:327-333.
  6. Beissinger, S. R. 1995. Modeling extinction in periodic environments: Everglades water levels and snail kite population viability. Ecological Applications 5:618-631.
  7. Bennetts, R. E., W. A. Link, J. R. Sauer, and P. W. Sykes, Jr. 1999. Factors influencing counts in an annual survey of Snail Kites in Florida. Auk 116:316-323.
  8. Bent, A.C. 1937. Life histories of North American birds of prey. Part 1. Bull. U.S. Natl. Mus. 137. 409 pp.
  9. Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1992. Birds in Jeopardy: the Imperiled and Extinct Birds of the United States and Canada, Including Hawaii and Puerto Rico. Stanford University Press, Stanford, California. 259 pp.
  10. Fisher, A.K. 1893. The hawks and owls of the United States in their relation to agriculture. Washington U.S. Dept. of Agriculture Bull. no. 6. 210 pp.
  11. Friedmann, H. 1950. The birds of North and Middle America. Part XI. U.S. National Museum Bull. 50.
  12. Harrison, C. 1978. A Field Guide to the Nests, Eggs and Nestlings of North American Birds. Collins, Cleveland, Ohio.
  13. Johnsgard, P. A. 1990. Hawks, eagles, and falcons of North America. Smithsonian Inst. Press, Washington, D.C. xvi + 403 pp.
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  15. Matthews, J.R. and C.J. Moseley (eds.). 1990. The Official World Wildlife Fund Guide to Endangered Species of North America. Volume 1. Plants, Mammals. xxiii + pp 1-560 + 33 pp. appendix + 6 pp. glossary + 16 pp. index. Volume 2. Birds, Reptiles, Amphibians, Fishes, Mussels, Crustaceans, Snails, Insects, and Arachnids. xiii + pp. 561-1180. Beacham Publications, Inc., Washington, D.C.
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  17. Palmer, R. S., editor. 1988a. Handbook of North American birds. Vol. 4. [Diurnal raptors, part 1]. Yale University Press, New Haven, CT. vii + 433 pp.
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  19. Reichert, B. E., C. E. Cattau, R. J. Fletcher, Jr., P. W. Sykes Jr., J. A. Rodgers Jr., and R. E. Bennetts. 2015. Snail Kite (<i>Rostrhamus sociabilis</i>), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.
  20. Reichert, B. E., C. E. Cattau, R. J. Fletcher, Jr., P. W. Sykes Jr., J. A. Rodgers Jr., and R. E. Bennetts. 2020. Snail Kite (<i>Rostrhamus sociabilis</i>), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. Online: https://doi.org/10.2173/bow.snakit.01
  21. Ridgely, R. S., and J. A. Gwynne, Jr. 1989. A guide to the birds of Panama with Costa Rica, Nicaragua, and Honduras. Second edition. Princeton Univ. Press, Princeton, New Jersey. 534 pp.
  22. Snyder, N. F. R., and H. W. Kale, II. 1983. Mollusk predation by snail kites in Colombia. Auk 100:93-97.
  23. Snyder, N. F. R., S. R. Beissinger, and R. E. Chandler. 1989. Reproduction and demography of the Florida Everglade (snail) kite. Condor 91:300-316.
  24. Stiles, F. G. and A. F. Skutch. 1989. A guide to the birds of Costa Rica. Cornell University Press, Ithaca, New York, USA. 511 pp.
  25. Sykes, P. W., Jr. 1984. The range of the snail kite and its history in Florida. Bull. Florida State Museum, Biological Science 29(6):211-264.
  26. Sykes, P.W., Jr., J.A. Rodgers, Jr., and R.E. Bennetts. 1995. Snail Kite (<i>Rostrhamus sociabilis</i>). In A. Poole and F. Gill, editors, The Birds of North America, No. 171. Academy of Natural Sciences, Philadelphia, and American Ornithologists' Union, Washington, DC. 32 pp.
  27. Takekawa, J. E., and S. R. Beissinger. 1989. Cyclic drought, dispersal, and the conservation of the snail kite in Florida: lessons in critical habitat. Conserv. Biol. 3:302-311.
  28. Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.
  29. U.S. Fish and Wildlife Service (USFWS). 1980. Selected vertebrate endangered species of the seacoast of the United States-- the Florida Everglade kite. FWS/OBS-80/01.32. 5 pp.
  30. U.S. Fish and Wildlife Service (USFWS). 1986. Florida snail kite (<i>Rostrhamus sociabilis plumbeus</i> Ridgeway) revised recovery plan (formerly called the Everglade kite). 57 pp.
  31. U.S. Fish and Wildlife Service (USFWS). 1990. American woodcock management plan. USFWS, Office of Migratory Bird Management. 11 pp.
  32. U.S. Fish and Wildlife Service (USFWS). 2023. Endangered and Threatened Wildlife and Plants; Technical Corrections for Eight Species of Endangered and Threatened Fish and Wildlife. Federal Register 88(181):64824-64831.
  33. U.S. Fish and Wildlife Service (USFWS). 2023. Everglade Snail Kite (<i>Rostrhamus sociabilis plumbeus</i>). 5-Year Review: Summary and Evaluation. U.S. Fish and Wildlife Service Southeast Region Florida Ecological Services Field Office. 13 pp.