Heliornithidae

(vertebrate zoology) The lobed-toed sun grebes, a family of pantropical birds in the order Gruiformes.

(Heliornithidae)

Class: Aves

Order: Gruiformes

Suborder: Heliornithes

Family: Heliornithidae

Thumbnail description
Medium-sized aquatic birds with long neck, sharply pointed bill, short legs, and brightly colored, lobed (rounded) toes; sexes differ in head and neck plumage

Size
10.2–23.2 in (26–59 cm); 0.26–1.9 lb (120–880 g)

Number of genera, species
3 genera; 3 species

Habitat
Thickly vegetated margins of rivers, lakes, and swamps

Conservation status
Vulnerable: 1 species

Distribution
Central and South America, sub-Saharan Africa, south and southeast Asia

Evolution and systematics

On the basis of skeletal and muscular characteristics, the family Heliornithidae is included in the Gruiformes, but its relationships to other families within the order are unclear. Similarities in superficial features and feather lice suggest a close link with the Rallidae, but there are also strong superficial resemblances to other waterbird families not considered closely related, especially the grebes (Podicipedidae). DNA-DNA hybridization suggests that the closest relative of the sungrebe (Heliornis fulica) may be the limpkin (Aramus guarauna) but material from the other sungrebe species has not been studied.

The family contains three monospecific genera. Similarities between the masked finfoot (Heliopais personata) and the African finfoot (Podica senegalensis), and differences between these species and the sungrebe, have led to the proposed separation of the sungrebe into the subfamily Heliornithinae and the other species into the subfamily Podicinae.

Physical characteristics

Sungrebes have a long neck; slender body; sharp pointed bill; brightly colored feet with lobed toes and sharp claws; and a long, broad tail. The African finfoot has a claw on the mobile first digit of each wing, which may be used when climbing. It also has stiffened rectrices and often swims with the tail spread flat on the water. This feature may increase maneuverability in water or on land. The masked finfoot has less stiffening and the sungrebe none.

The legs and feet are brightly colored: orange in the African finfoot, pea green in the masked finfoot, and yellow with black stripes in the sungrebe. Bill colors are also bright. All species have predominantly brown upperparts (spotted white in the African finfoot), a patterned head and neck with a white stripe down the side of the neck, and white underparts (variably barred with brown in the African finfoot). The very dark race Podica senegalensis camerunensis of the African finfoot lacks spotting on the upperparts and white on the head and neck.

In all species the sexes differ somewhat in the head and neck plumage pattern. The African finfoot varies in size, both geographically and sexually (males may be 25% larger than females).

Distribution

The family is distributed across three continents. The African finfoot is widespread in sub-Saharan Africa, except in the arid northeast and southwest, while the sungrebe occurs widely in Central America and northern South America. The masked finfoot ranges from Bangladesh and northeast India to Southeast Asia, the Malay Peninsula, and Sumatra. This wide geographic distribution suggests an ancient lineage, while similarities among the widely separated species suggest that the family formerly had a wider and more continuous distribution.

Habitat

All species require water with fringing, dense cover. Habitats range from coastal creeks and mangrove swamps to mountain streams up to about 6,600 ft (2,000 m) above sea level. The birds may inhabit fast-flowing streams, but most often they occur on still or slow-moving water at ponds, lakes, dams, estuaries, rivers, and streams. They are rarely found far from shoreline cover, which may be woody, with overhanging trees or bushes, or emergent. African finfoot are sometimes found on water adjacent to bare rocks. Other habitats include flooded rainforests, papyrus swamps, and reedbeds with woody vegetation.

Behavior

Members of the sungrebe family are usually recorded singly, in pairs, and in family groups; and probably permanently territorial. Sungrebe species are most active in the early morning and the evening and are usually very shy, skulking, and elusive. The birds keep close to cover when swimming, and when disturbed, they seek fringing cover or freeze with the head lowered and the body submerged. Sungrebes swim well, with exaggerated backward and forward movements of the head and neck, but these species also move nimbly on land, with the body carried quite erect, climbing into trees and bushes to roost.

Vocalizations are rarely heard. The African finfoot makes a booming sound when breeding, the masked finfoot utters a bubbling call, and the sungrebe has an "eeyooo" territorial call.

Although no species is known to be regularly migratory, newly available waterbodies are colonized quite rapidly, and vagrancy is recorded in the sungrebe and the masked finfoot. The latter species may be a passage migrant and winter visitor in Thailand and is possibly a winter visitor to the Malay Peninsula and Sumatra.

Feeding ecology and diet

All species eat predominantly insects, especially adult and larval midges, mayflies, and dragonflies but also grasshoppers, flies, and beetles. Mollusks are frequently taken, and crustaceans (shrimps, crabs, and prawns), worms, millipedes, and spiders are recorded in their diet. Frogs, tadpoles, small fish, and small amounts of seeds and leaves are eaten.

Much food is taken from the water surface. Some items are picked from rocks and fringing or overhanging vegetation, with birds sometimes jumping out of the water to take prey. They also forage on land, especially along banks.

Reproductive biology

Sungrebes are monogamous and usually breed when water levels are high. Courtship in the African finfoot involves one bird raising and opening its wings alternately while swimming, while the other bird makes a snapping sound from cover. Courting sungrebes swim in counter circles with lowered necks and half-raised wings.

The nest is a shallow bowl of sticks, twigs, grass, and reeds lined with dead leaves and usually built in thick vegetation over water, especially on clumps of debris caught in branches after floods. Clutch size is two to three eggs in sungrebe species, although some sources note up to seven eggs in a nest. In sungrebe species, both sexes share nest building and incubation responsibilities. Incubation periods appear remarkably short: only 10–11 days in the sungrebe, which is unique in the family in having altricial (naked and helpless) chicks, born blind, that are carried around by the male in a pocket of skin under each wing. The chicks of the other species are semi-precocial (precocial describes young covered in down that are able to move about when first hatched); those of the African finfoot remain in the nest for at least two days after hatching.

Conservation status

The masked finfoot is classed as globally Vulnerable with a small population (2,500–10,000 birds in 2000) that is declining due to the loss and degradation of wetlands, deforestation, mangrove destruction, agriculture, disturbance, and hunting. The African finfoot is Vulnerable in South Africa, where its population was 500–1,000 individuals in 2000 and where it is threatened by rapid habitat loss. Such threats must apply to all species throughout their ranges, as their habits everywhere are under great pressure. Because all species of the sungrebe family are inconspicuous, significant population declines may easily pass unnoticed.

Significance to humans

Sungrebe habitats are usually not densely populated by human beings, and the retiring birds of this family rarely come into contact with people. They do not compete with people for food resources, and their population densities are so low that they often are not a significant human food item or hunting target, although the globally threatened masked finfoot is hunted and its eggs and chicks are also taken. Sungrebe species do not figure significantly in local legends.

Species accounts

Resources

Ali, S., and S.D. Ripley. Handbook of the Birds of India and Pakistan. Compact ed. Delhi: Oxford University Press, 1983. del Hoyo, J., A. Elliott, and J. Sargatal. Handbook of the Birds of the World, Vol. 3. Barcelona: Lynx Edicions, 1996.

Sibley, C.G., and B.L. Monroe. Distribution and Taxonomy of Birds of the World. New Haven: Yale University Press, 1990.

Sibley, C.G., and J.E. Ahlquist. Phylogeny and Classification of Birds: A Study in Molecular Evolution. New Haven: Yale University Press, 1990.

Stattersfield, A.J., and D.R. Capper, eds. Threatened Birds of the World: The Official Source for Birds on the IUCN Red List. Cambridge, United Kingdom: BirdLife International, 2000.

Urban, E.K., C.H. Fry, and S. Keith, eds. The Birds of Africa, Vol. 2. London: Academic Press, 1986.

Alvarez del Toro, M. "On the Biology of the American Finfoot in Southern Mexico." Living Bird 10 (1971): 79–88.

Brooke, R.K. "Taxonomic Subdivisions within the Heliornithidae." Bull. Oriental Bird Club 20 (1994): 28–31.

Chong, M.N.H. "Masked Finfoot (Heliopais personata) in Peninsular Malaysia." Ostrich 55 (1984): 171–173.

Skead, C.J. "Peters' Finfoot (Podica senegalensis) at the Nest." Ostrich 33 (1962): 31–33.

Birds of the World, Sun-grebes, Finfoots. Department of Ecology and Evolutionary Biology, Cornell U. 27 Feb. 2002.

[Article by: Barry Taylor, PhD]

Heliornithidae
African Finfoot (adult female)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves Order: Gruiformes Family: Heliornithidae GR Gray, 1840
Genera and Species
Podica senegalensis Heliopais personata Heliornis fulica

The Heliornithidae are a small family of tropical birds with webbed lobes on their feet similar to those of grebes and coots. The family overall are known as finfoots, although one species is known as a Sungrebe. Finfoots somewhat resemble rails, they have long necks, slender bodies, broad tails and sharp pointed bills. They have a diverse range of calls, but do not call frequently. Their legs and feet are brightly coloured and unlike grebes they are capable of walking well and even moving quickly on land. There are three species. The African Finfoot is found in tropical Africa on streams in woodland. The Masked Finfoot has a scattered distribution from Eastern India down through southeast Asia to the Wallace Line. The Sungrebe is found in tropical Central and South America. Finfoots are highly secretive and many aspects of their biology are unknown to science.

Finfoots are found in numerous habitats in the tropics as long as there is water and cover. It is uncertain why cover is so essential to finfoots, but they are extremely secretive and often overlooked. Their ranges extend from coastal creeks to fast moving mountain streams, most commonly being found in large slow moving bodies of water. Swamps, reedbeds, mangroves and forest are also used by them. Finfoots are territorial, probably for much of the year and certainly when breeding. They are also are not thought to undertake regular migrations, but some birds do regularly disperse and they are quick to colonise new areas of suitable habitat.

Finfoots feed on a wide range of foods, insects of various sorts being the most frequently observed component of their diet. Little quantitative information on finfoot diet exists, but they have also been recorded eating molluscs, crustaceans, spiders, frogs, fish and some leaves and seeds. Unlike grebes they do not dive to obtain food, but instead feed by picking prey off the water's surface or foraging on the shore.

All three species tend to breed after the wet season, the exact timing of which being dependent on the local climate. The breeding behaviour of the Masked Finfoot is almost entirely unknown. All three species exhibit some changes in appearance prior to breeding - Masked Finfoots develop a fleshy knob above the bill, and the plumage of the male African Finfoot and female Sungrebe also change. There is considerable variation within the finfoots on several aspects of breeding; in the Sungrebe the nest building and incubation duties are shared between the sexes, in the African Finfoot the female alone incubates. The nests of all finfoots are untidy bowls of sticks, twigs and reeds suspended in vegetation above water.

Species

• African Finfoot, Podica senegalensis
• Masked Finfoot, Heliopais personata
• Sungrebe, Heliornis fulica

References

• Bertrand, B. C. R. (1996). "Family Heliornithidae (Finfoots)" in del Hoyo, J., Elliott, A., & Sargatal, J., eds. Handbook of the Birds of the World. Vol. 3. Lynx Edicions, Barcelona, ISBN 84-87334-20-2

External links

• Heliornithidae videos on the Internet Bird Collection

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Heliornithidae

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