All species › Birds of prey › Kites, Old World vultures, eagles and hawks › Snail Kite
Snail Kite | Rostrhamus sociabilis
Slakkenwouw | Caracolero común
The Snail Kite eats almost nothing but apple snails, freshwater snails the size of a plum, and its whole build is shaped around that one food. Within the area of this guide it lives only in the marshes of Florida, at the extreme northern edge of a range that runs on through Central and South America.
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Voice
The sound most often heard is a fast rattling alarm series, ka-ka-ka-ka-ka, given as soon as anyone approaches a nest or a roost. It also has a softer bleating k-a-a-a-a-a that sounds like a sheep and is used mainly between members of a pair. The contact note is a quieter kuk-kuk, audible only at close range. Outside the breeding season the species is largely silent; a group at a communal roost gives itself away by movement rather than by voice.
Recording: Jacob Wijpkema — CC BY-NC-SA 4.0 · San Joaquin (near Monte Villa), Yacuma, Departamento del Beni, Bolivia · xeno-canto
Identification
The bill is the mark: thin, deeply hooked and sharply pointed, three to four centimetres long, built to lift the muscular body of a snail out of its shell without breaking the shell. The male is dark slate-grey with blacker wings and a black tail showing a white base and a white tip; the bare skin around bill and legs is reddish pink. The female is browner, with whitish feathering around the face, and is slightly the larger of the two, as in nearly all hawks and kites. Juveniles are brown above and streaked brown and buff below, with a broad buff eyebrow and throat. In flight the broad, almost paddle-shaped wings stand out, and the beat is slow and rather floppy; the bird quarters low over the marsh with its head angled downwards.
Confusion species
Northern Harrier (Circus hudsonius) hunts the same marshes at the same height and causes most confusion, especially with juvenile kites; the harrier shows a white rump rather than a white tail base, holds its wings in a shallow V, and has a short ordinary raptor bill. Adult males are distinctive in good light thanks to the red facial skin and the slim hooked bill. Against the light, wing shape decides it: broad and rounded on the kite, narrow and long on the harrier. A third pitfall is Black Vulture, which also drifts low over marsh but is much larger, has no white in the tail and never drops to the water.
Habitat
Extensive freshwater marshes, shallow lake margins and slow-moving waterways with clear water and scattered stands of reed, sedge or sawgrass. The habitat is defined entirely by the apple snail: where the snail is absent the kite is absent, however suitable the marsh may look. Visibility matters just as much, for the bird hunts by sight; if aquatic vegetation grows too dense or the water turns turbid it can no longer see the snails and abandons an otherwise good marsh. Canals, cattle ponds and man-made water storage areas are used as soon as the snails colonise them. Low bushes and small trees along the edge are needed as lookouts and nest sites.
Where the bird is most often found, arranged by the USNVC — the vegetation classification of the United States and Canada — and CMECS for sea and coast.
Range and movements
Within this guide it is resident in central and southern Florida, in the Everglades and around the large lakes; beyond that it is numerous in the lowland marshes of Cuba, of the Mexican Gulf Coast and the Yucatán Peninsula, and south through Central America. On the Pacific side of Mexico its range has moved north in recent decades as far as Jalisco and Colima, hundreds of kilometres beyond the previously published limit. It does not migrate, but it is markedly nomadic: in drought whole groups leave a dried-out marsh and turn up elsewhere. In cold winters Florida birds sometimes shift southward within the state.
- Resident
- Breeding (summer)
- Winter
- Passage
- dark = core range, pale = thinly spread
Where and when to look
In Florida, look along the edge of a large shallow lake or marsh in early morning — Lake Okeechobee, Lake Kissimmee, the Everglades — and watch for the slow, low, head-down quartering flight. When the bird banks, the white tail base flashes; at distance that is the most reliable mark of all. A kite that has settled on a low bush with a snail, tugging at the shell in small jerks, stays in the same spot for minutes on end.
Conservation
Worldwide the species is numerous and listed as Least Concern (LC), but the United States population is federally listed as endangered and fluctuates widely: from about 65 birds in 1972 to some three thousand at the end of the 1990s, followed by a renewed slump and a recent recovery. Everything depends on water level: prolonged high water or a deep drought removes the snails and nesting fails, so water management in south Florida directly governs how many kites there are. The introduced island apple snail was at first too large for young birds to handle, but it now provides an important part of the food supply in many areas.
Scientific name
Rostrhamus sociabilis | (Vieillot, 1817)
Vieillot described the species in 1817 as Herpetotheres sociabilis; because it was later placed in another genus, author and year stand in parentheses. The generic name Rostrhamus combines Latin rostrum, 'bill', with hamus, 'hook', and so describes exactly the tool on which the bird's existence depends. sociabilis means 'sociable', 'living in company', after its habit of hunting, roosting and nesting in groups. The described specimen came from Corrientes, near the Rio de la Plata in Argentina. Florida birds are referred to the subspecies R. s. plumbeus, which also occurs in Cuba.