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Species Name:    Aramus guarauna
Common Name:                 Limpkin

 

I. TAXONOMY

Kingdom Phylum/Division: Class: Order: Family: Genus:
Animalia Chordata Aves Gruiformes Aramidiae Aramus
 

Species Name: 
Aramus guarauna Linnaeus, 1766.

Common Name:
Limpkin.

Synonymy:
Aramus scolopaceus, based on a name given by Gmelin in 1789. .

Other Taxonomic Groupings:
Two subspecies exist: A. guarauna guarauna, and A. g. pictus.

Species Description:
rail-like wading bird, about the size of a White Ibis (Eudocimus albus). Mass 0.9-1.3 kg. Wings broad and rounded; wingspan about 1 m. Plumage uniform dark olive-brown, paler on face, chin, and throat, with slight bronze iridescence on wings and especially tail. Most feathers have triangular white markings, largest on wings and back, giving spotted appearance. Juvenile similar in color to adult but has narrower white triangles, giving streaked (not spotted) appearance. Legs and feet dull olive-black. Strong flier, runner, and swimmer; climbs and perches readily on tree limbs. Male usually larger than female, with distinctly different call; otherwise sexes difficult to distinguish in the field. Sometimes sulking and secretive in riparian vegetation but at other times extremely prominent, with loud and repetitive calling. Congregates in loose colonies in areas of optimal habitat but apparently also where habitat is uniform and widespread.

Basic plumage mostly dark olive-brown, darkest on hindneck, interscapulars, and lower back, with bronzy or purplish iridescence on wings and especially tail. Ends of primaries darker than wing-coverts; tail-feathers even darker brown. Lores, malar region, chin, and upper throat dull white and unmarked or faintly streaked with brown. Most feathers, except primaries and rectrices, have wide white streak along shaft that comes to point at end of feather. Overlapping of larger feathers creates bold, bright-white triangles on back, scapulars, and especially wing-coverts. Toward neck, triangles become much narrower and appear as streaks, giving whitish cast to neck and head. White triangles on wing-coverts can be helpful in field in identifying sex of adults. Probably because adult males generally larger than females, wing-covert triangles seem wider, longer, and more prominent than do those of females. Long triangles on 1 or 2 outermost (largest) greater-coverts usually visible on male but hidden on female (Bryan 1996b

Bill twice as long as head; slender, compressed, slightly decurved, both mandibles laterally grooved for about two-thirds their length (Gosse 1847, Coues 1903). Bill of equal width almost from base to tip. A gap in bill (edges of bill do not quite meet in center of bill) may function by making ends tweezerlike for better grasping of prey (A. Wetmore in Howell 1932). Lower mandible curved to right in all juveniles and adults; upper mandible often curved, but not as prominently. Underlying bone usually not curved (Snyder and Snyder 1969).

Eyes rather large (Audubon 1840). Iris Vandyke brown; eyelid dull yellow.Downy young have dark legs and feet (Nicholson 1928). During week 3, legs begin to lengthen noticeably; until shortly after starting to fly, juvenile has noticeably thicker, paler legs (Ingalls 1972, Nesbitt 1978). Adult tarsus and toes dull olive black; claws darker, nearly black (Wetmore 1965). Tibia bare in its lower half; tarsus long, compressed, anteriorly broad scutellate. Feet very long, rather stout

Males usually larger than females. Ten males measured; all measurements given in cm, mean (range): wing length 31.3 (30.0-32.5); tarsus 13.0 (10.8-14.0); culmen 12.6 (11.6-13.5). Four females measured: wing length 30.5 (30.3-31.6); tarsus 12.6 (11.1-13.5); culmen 12.0 (11.7-12.6; all Florida specimens; Peters 1925). Average body mass for 4 adult males from Leon and Lake Cos., FL, was 1,240 g (range 1,130-1,370); for 4 adult females 1,080 g (range 1,050-1,170; Bryan 1981). Thirty-one unsexed adults in Marion Co., FL, averaged 1,080 g (range 900-1,270; Nesbitt et al. 1976).

Most easily confused in the field with immature White Ibis and immature Glossy Ibis (Plegadis falcinellus), but distinguishable by overall chocolate-brown color, white-spotted appearance, straighter and thicker bill, and dark legs. Immature Black-crowned Night-Heron (Nycticorax nycticorax) and Yellow-crowned Night-Heron (Nyctanassa violacea) are brown and about the same size but have shorter necks and short, straight bills and paler legs.

Hatchlings have long, thick, soft down; often described as black, and even shiny black and jet black (Audubon 1840, Sprunt 1948, L. Walkinshaw unpubl.). Within 2-3 d, color becomes very dark brown or dark brownish black, with lighter umber around eyes (Ingalls 1972, Walkinshaw 1982). Color change may result from fading but not yet explained. Over first 2 wk, down becomes progressively lighter, varying from cinnamon brown to snuff brown, generally darker above and paler below, with chin, throat, and upper foreneck, indistinct supercilium, malar region, and upper belly dull white (Bent 1926, Wetmore 1965). Older downy young and juveniles often appear to have rusty-colored crowns (DCB).Remiges begin to emerge at week 3. During week 4, feathers with white streaks develop on wings and scapular region, followed by feathers of tail, back, wing-coverts, and back of neck. At end of week 4, down remains only on top of head, neck, and rump. Down on head and neck appears much paler and supercilium more distinct. Next, streaked feathers develop on the breast. By the end of week 5, juvenile fully feathered with no down apparent (Ingalls 1972).


Potentially Misidentified Species:
T

II. HABITAT AND DISTRIBUTION 

Regional Occurrence:
Resident throughout most of Florida.Throughout the Bahamas (where generally rare except Andros and Eleuthera) and Greater Antilles, including Cuba, Isle of Youth, Jamaica (local), Hispaniola (uncommon), and formerly Puerto Rico, where now extirpated. Atlantic slope of Mexico south to Brazil and Argentina.

IRL Distribution:
S


III. LIFE HISTORY AND POPULATION BIOLOGY

Age, Size, Lifespan:
A

Abundance:
S

Reproduction:
some monogamy; some serial polyandry. Unmated female visits several territories, finally settling on territory of kow-calling unpaired male.After pair-bonding, pairs mostly forage and rest side by side until incubation.Copulation continues from pair formation until incubation starts, with slight increase in frequency during week preceding incubation; also occurs between laying eggs (Ingalls 1972). Male initiates copulation with soft rattling and clucking, approaching slowly with neck straight and bill angled slightly downward. Female ceases activity and turns away in silence, lowering head slightly, gradually bending legs, extending wings horizontally, lowering neck, and angling bill perpendicular to ground, lying almost flat on ground. Male steps onto female's back, bends legs and elevates wings for balance, and depresses tail. Male sometimes pecks at female's neck or scapular region, or grasps neck at base of head, sometimes twisting head slightly to one side. Cloacal contact lasts about 3 s and entire mounting lasts =60 s. Male dismounts over female's head or to side. After dismounting, both usually engage in such activities as brief calling, tail-shaking, feather-ruffling, preening, wing-flicking, probing, or stretching (Ingalls 1972). Displacement-nesting activity, specifically vegetation-tossing by male and female, also observed (N. Snyder pers. comm., in Ingalls 1972).

Female's desertion of family unit usually occurs 1-5 wk after young are in downy stage, when female starts to forage and rest in distant parts of territory. Some pair bonds persist over several seasons. Male continues to care for young. Female desertion especially quick after heavy mortality of downy young, but females also seen to desert when up to 4 young still surviving in brood. After wandering, female may return to same male for second mating.


Embryology:
Egg length × breadth (mm): 60.08 (range 55.58-63.89) × 43.98 (range 41.72-45.80); mass of 57.4 g (Walkinshaw 1982). Ground color buff; 2 types noted: light grayish white and buffy brown, shades varying but never light and dark within set (Nicholson 1928). Blotched and streaked markings, especially heavy at large end, of brown and purplish gray. Overall average 5.5 eggs/clutch.

Both parents incubate during daytime; only female incubates at night (Bryan 1981).

Juveniles fly by age 7 wk (Ingalls 1972). Young stay in close group while still being fed by parents. By weeks 8-10, juveniles begin to wander to separate places, although still somewhat grouped within parents' territory. At weeks 11-13, juvenile males become target of increasing parental aggression, leave sibling group, and assume well-defined subterritories within parents' territory. Subterritories usually stable until dispersal. Juvenile females, by contrast, are characteristically silent and unaggressive, range throughout parents' territory, forage and rest longer near parents (especially adult male), and disperse later (Bryan 1981, 1996a). First brood may stay in parents' territory while second brood is young or may be driven out (Ingalls 1972).Male juveniles leave parents' territory 13-17 wk after hatching, depending on parental pressure (Bryan 1981, Walkinshaw 1982).

Both males and females breed successfully near end of first year (as early as 44 wk old). Prolonged courtship and subsequent desertion sometimes occur in first attempt of 1-yr-old birds (Bryan 1981). Number of clutches/breeding season 1-3; frequencies of each not reported. Second clutches often laid soon after parental care stops for first brood at about week 10.


IV. PHYSICAL TOLERANCES

Temperature:
U

Salinity:
S

Other Physical Tolerances:
T

Dissolved oxygen:
J

V. COMMUNITY ECOLOGY

Trophic Mode:
Forages mostly by walking in shallow water, rarely so deep as to immerse one-half the body, Occasionally eats lizards, frogs, insects, crustaceans, and worms; may be especially useful when forced into suboptimal habitats during drought and flooding (Baird et al. 1884, Harper 1941, Stevenson and Anderson 1994).

Competitors:
Apple snails, the primary food, also important to young alligators (Fogarty and Albury 1967), Snail Kites (Rostrhamus sociabilis), and Boat-tailed Grackles (Quiscalus major; Snyder and Snyder 1969). Snail Kites known to attack and steal snails from Limpkins in drought situations (Bourne 1983, Miller and Tilson 1985).

Predators:
Alligator known to take adults (Ingalls 1972); snake, crow, raccoon (Procyon lotor), "water-rat" (probably round-tailed muskrat [Neofiber alleni]).American alligators (Ingalls 1972). Predators of downy young unreported. Eggs eaten by water-rats, raccoons, and crows (D. Nicholson unpubl.). Egg predation also reported by large yellow snake

Parasites:
trematodes Cyclocoelidae (100%), Lyperorchis lyperorchis (56%), Echinostomatidae (33%), and Pronosoma serratum (11%); and nematodes Amidostomum acutum (56%) and Strongloides sp. (33%). No blood parasites detected. Fewer species of helminths than other gruiforms in Florida, possibly because of more restricted diet. Biting lice Laemobothrion cubense and Rallicola funebris also found (Conti et al. 1985). Three genera of Mallophaga (Sibley and Ahlquist 1972).

Associated Species:
Distribution of apple snail, a key component of diet, appears to best predictor of breeding distribution of Limpkin rangewide (Harper 1936). Apple snail is restricted to Florida and s. Georgia; habitat in n. Florida occurs mostly in spring-fed rivers that remain relatively warm in winter (Clench and Turner 1956).

Habitats:
Usually considered nonmigratory During observations over 2 breeding seasons in Florida (at Alexander Springs [Lake Co.] and Wakulla Springs [Wakulla Co.]), most males remained on territory, but most females (including some color-banded) and a few males disappeared in early summer after breeding and did not return again until late winter, sometimes to the same breeding territories (Bryan 1981). Migration also possible between Cuba and Florida

Resident of open freshwater marshes, riparian swamp forests (especially those bordering slow-moving rivers and spring runs), and lake and pond shores (Robertson and Woolfenden 1992). Specific habitat quantification not published. Typical trees and shrubs in these habitats include bald cypress (Taxodium distichum), cabbage palm (Sabal palmetto), live oak (Quercus virginiana), red maple (Acer rubrum), southern willow (Salix caroliniana), wax myrtle (Myrica cerifera), and dahoon holly (Ilex cassine). Shrubs important for nesting are frequently draped in vines, typically climbing hempweed (Mikania scandens), poison ivy (Rhus radicans), grape (Vitis spp.), and Virginia creeper (Parthenocissus quinquefolia).

Activity Time:
M


VI. SPECIAL STATUS

Special Status:
T

In Florida, 1920s drainage of many parts of Everglades and southwest shore of Lake Okeechobee eliminated several formerly abundant populations(Birds of No Am).

Florida Fish and Wildlife Conservation Commission estimated population by creating map of potential habitat and using 2 density estimates (5-10 territories/km2 for forested wetland systems and 2.5-5 territories/km2 for open wetland systems); this estimated statewide population of 3,000-6,000 territories in current conservation areas, which represented 49% of all potential wetland habitat (Cox et al. 1994).

Once abundant throughout the Florida Peninsula but almost extirpated in accessible regions by hunting for food (Bent 1926). Overhunting steadily decreased populations described as "very abundant" in 1860s to "decidedly scarce" 40 yr later.By 1954, Florida population strengths were Wakulla Springs, Kissimmee River valley to western shore of Lake Okeechobee; also a building population in the Everglades around Paradise Key (Sprunt 1954).

Population losses due to wetland conversion in Florida not documented, but must have been large. Over half of wetlands within central and s. Florida lost during last century; remainder highly fragmented and severely degraded. Wading-bird populations reduced to <10% of former size (Weaver and Brown 1993). Beginning in early 1900s, and accelerating in 1940s and 1950s, farmers and developers diked and drained thousands of acres of broad marshy headwaters of northward-flowing St. Johns River. To the west, the southward-flowing Kissimmee-Okeechobee-Ever-glades drainage basin was also manipulated by works of Everglades Drainage District and Okeechobee Flood Control District. However, these efforts were dwarfed during 1950s and 1960s when U.S. Army Corps of Engineers greatly accelerated large-scaled drainage with 46,600-km2 Central and Southern Florida Project for Flood Control. By 1972, about 70% of historical 164,000-ha Upper St. Johns River Marsh was converted to agricultural fields (Sterling and Padera 1998). Almost half the historic 1.2 million-ha greater Everglades wetland system was also drained for agriculture and development (Davis et al. 1994). Because of these water diversions, marsh drydowns became more frequent and longer in duration and were blamed for suppressing apple-snail populations (Kushlan 1975).

Water-level manipulations continue to be a problem. At Lake Okeechobee, whose western littoral zone is particularly important Limpkin habitat, wading-bird populations have dropped 70% since the 1980s and submergent plant communities were reduced by 70% during the 1990s. Pollution of freshwater habitats may also be a problem. Much of the water now flowing into the Everglades originates as agricultural runoff from citrus groves and sugarcane fields. Apple-snail habitat in rivers and lakes also has been degraded by invasive exotic aquatic plants that locally replace native plant populations.

Listed as Species of Special Concern by Florida Fish and Wildlife Conservation Commission. The Florida Natural Areas Inventory lists it G5 (demonstrably globally secure) and S3 (in Florida either very rare and local throughout range [21-100 occurrences or <10,000 individuals] or found locally in very restricted range or vulnerable to extinction from other factors; Marois 1999). Several factors suggest species may continue to be vulnerable in U.S.it is relatively uncommon in small range, wholly dependent on certain riparian habitats, and largely dependent on a single prey species. The Snail Kite, another apple-snail specialist, also once ranged to Wakulla Springs (Howell 1932), but is now reduced to s. Florida and listed as Endangered. Nevertheless, Limpkin does not seem to be in immediate danger and will probably remain locally common where apple snails are abundant.

Florida Fish and Wildlife Conservation Commission has proposed additional habitat protection. Commission staff used estimates of territory size in 2 habitat types (forested riverine wetlands and open wetlands) and calculated acreage of potential habitat from LANDSAT imagery. Analysis determined that approximately 1,981 km2 of potential habitat for Limpkins exist throughout Florida, of which 49% occurs within current conservation areas. Conservation-area habitat suggested 4 potentially secure populations (>100 territories), 11 insecure populations (25-100 territories), and >30 imperiled populations (<25 territories). Four largest populations in current conservation areas are in: (1) Everglades (including Everglades National Park, water-conservation areas, Big Cypress National Preserve, Fakahatchee Strand Preserve State Park, and Loxahatchee National Wildlife Refuge [NWR]); (2) water-management district lands along western edge of Lake Okeechobee; (3) forested wetlands on and near Ocala National Forest (including Lake Woodruff NWR and Cross-Florida Greenway lands); and (4) water management-district lands along upper St. Johns River. Analysis concluded that current conservation areas appear insufficient to provide minimum habitat for Limpkins (enough to support at least 10 populations of 200 individuals each) and that more habitat area should be conserved by acquisition and/or regulation. Increased efforts proposed to: (1) expand those conservation areas holding insecure populations; (2) create new noncontiguous conservation areas where habitat occurs; and (3) create new noncontiguous conservation areas where concentrations of breeding bird-atlas records occur. Additional Strategic Habitat Conservation Areas for suites of rare species, including Limpkin, have also been identified for public acquisition (Cox et al. 1994).

No significant conservation measures taken specifically for Limpkin, although it certainly benefited in the past from wading bird anti-shooting campaigns and general bird protection legislation. More recently, the large-scaled wetland conversions have now stopped (see Effects of human activity, above) and wetland-restoration efforts are increasing.The most far-reaching effort will be the 35-yr, US$8 billion Comprehensive Everglades Restoration Plan led by the U.S. Army Corps of Engineers, which includes more than 65 projects that will restore about 972,000 ha of the wetland's ecosystem.

The Limpkin is known to breed successfully only where substantial apple-snail populations occur. Apple-snail ecology, habitat use, water-quality needs, distribution, and conservation status remain poorly known and should be determined throughout Florida. This information should guide management practices that affect those habitats, including hydroperiod, prescribed fire, aquatic-weed control, and nutrient loading. Continued research is needed for effective control of invasive exotic plants, which threaten some apple-snail habitats. Research is also needed to improve regulations to prevent new invasive exotic threats, which might eventually include uncontrollable predators and diseases of the apple snail.



Fisheries Importance:  
A


VII. REFERENCES

Bryan, D. C. 2002. Limpkin (Aramus guarauna). In The Birds of North America, No. 627 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

 

Report by: K. Hill, Smithsonian Marine Station
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Page last updated: June 10, 2006