Sungrebes

(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

List of Species

African finfoot

Podica senegalensis

taxonomy

Heliornis senegalensis Vieillot 17, Senegal. Four subspecies.

other common names

English: Peter's finfoot; French: Grébifoulque d'Afrique; German: Binsenralle; Spanish: Avesol Africano.

physical characteristics

13.8–23.2 in (35–59 cm); 0.74–1.93 lb (338–879 g). Orange feet, brown or blackish back with variable white spotting. Underside light with variable barring.

distribution

P. s. senegalensis: Senegal east to eastern Democratic Republic of Congo (Zaire), Uganda, northwestern Tanzania and Ethiopia; P. s. somereni: Kenya and northeastern Tanzania; P. s. camerunensis: southern Cameroon, Congo and northern Democratic Republic of Congo; P. s. petersii: Angola east to Mozambique and south to eastern South Africa.

habitat

Permanent rivers, streams, and still waterbodies densely fringed with reeds and overhanging trees; also mangroves and flooded forests.

behavior

Territorial, each pair defending several hundred yards (meters) of waterway.

feeding ecology and diet

Forages in water and on land, taking invertebrates and small vertebrates.

reproductive biology

Breeds when water levels are high. Monogamous; lays two to three eggs; incubation at least 12 days, by female; young semi-precocial.

conservation status

Widespread; locally quite common but uncommon in eastern Africa and considered Vulnerable in South Africa.

significance to humans

None known.

Sungrebe

Heliornis fulica

taxonomy

Colymbus fulica Boddaert, 1783, Cayenne. Monotypic.

other common names

English: American finfoot; French: Grébifoulque d'Amérique; German: Zwergbinsenralle; Spanish: Avesol Americano.

physical characteristics

10.2–13 in (26–33 cm); 0.26–0.33 lb (120–150 g). Yellow and black banded feet, upper bill dark in male, red in female, lower bill pale. White throat, black on top of head to back of neck, brown back and pale underneath.

distribution

Southeastern Mexico through Central and South America south to Bolivia and northeastern Argentina.

habitat

Forest rivers and streams and freshwater lakes and ponds, with dense fringing and overhanging vegetation.

behavior

Permanently territorial; male defends about 200 yd (180 m) of stream bank.

feeding ecology and diet

Feeds from water surface, occasionally on land; eats mainly aquatic insects.

reproductive biology

Breeds in spring (northern part of range) or during rains. Two to three eggs; incubation 10–11 days, by both sexes; young altricial.

conservation status

Not threatened. Widespread but rarely observed; numbers unknown. Regarded as common to uncommon; population density probably low.

significance to humans

None known.

Resources

Books

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.

Periodicals

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.

Online

Birds of the World, Sun-grebes, Finfoots. Department of Ecology and Evolutionary Biology, Cornell U. 27 Feb. 2002. <http://www.eeb.cornell.edu/winkler/botw/heliornithidae.html>

Barry Taylor, PhD