• 3 species in the tropics worldwide
• DR personal total: 2 species (67%), 1 photo'd

The Heliornithidae is a small family of odd aquatic birds locally distributed in the tropics around the world. There are three species — each in a monotypic genus — and each fills a niche in the major tropical regions of the world. Both species in the Old World are called Finfoots; the single example in the New World is named Sungrebe (left). Don't be fooled by the name "Sungrebe." These are not remotely related to grebes but are most closely related to rails.

All species in this family have lobed feet — an adaptation for aquatic life — and feed primarily from the water by taking food items (crustaceans, amphibians, or invertebrates fallen into the water) at the surface (Bertrand 1996).

The Sungrebe frequents quiet backwaters along freshwater streams and rivers from Mexico to Argentina, but it is local and uncommon throughout its rage (Marc Fenner took this photo, right, in Costa Rica). Sungrebe sometimes found in the same habitat as Sunbittern, which shares a vaguely similar facial pattern (see Sunbittern page), but is in an entirely different Order.

Genetic data confirm the parameters of the traditional family Heliornithidae, but these data suggest that Heliornithidae is nested within Rallidae, with the African flufftails (Sarothrura) sister to "Heliornithidae" ((Fain et al. 2007, Hackett et al. 2008). More research is needed.

There are two finfoots in the Old World. African Finfoot — traditionally called "Peter's Finfoot" in southern Africa — ranges widely throughout tropical and southern Africa but is nowhere common. I've seen it in Uganda but before digital photography. Arthur Grosset photographed this African Finfoot (below) in Ghana.

Masked Finfoot Heliopais personata is a poorly known species from southeast Asia. It has become so scarce that it is listed now as Endangered. All finfoots are primarily resident, but Masked Finfoot has an odd distribution of records in Peninsular Malaysia and Sumatra that suggests migratory movement.

The lack of much basic information extends to all members in the group. In writing about this family, Bertrand (1996) says that "rather few bird families are as poorly known and as infrequently observed as the Heliornithidae."

In my brief experience the birds were shy and seen for only a brief time. Young African Finfoots are born precocial and ready to swim, but baby Sungrebes are born blink, almost naked, and helpless. The Sungrebe is already very strange in having a very short incubation period (10–11 days, matching some small passerines) but has an astonishing behavior entirely unique in the bird world: the male Sungrebe is able to transport these helpless offspring, even in flight! Bertrand (1996) explains:

"M. Alvarez del Toro, who observed a nesting pair in Mexico, discovered that the male has a shallow pocket under each wing into which the two young can fit. The pocket is formed by a pleat of skin, and made more secure by the feathers on the side of the body just below. The heads of the chicks could be seen from below as the bird flew. Alvarez del Toro collected the bird in order to examine it and confirm the unlikely discovery. Subsequently, he found it confirmed also by a report published by Prince Maximilian of Wied 138 years earlier but apparently ignored, forgotten or not believed. This adaptation is unique among birds: in no other species is there any mechanism whereby altricial young can be transported. Of course, the precocial young of some swans and grebes may hitch rides on their swimming parents' backs, and a male jaçana can transport his chicks about holding them between his wings and body, but neither of these cases applies when the adults are in flight.... The transport system of the Sungrebe raises numerous further questions. How do the chicks get into the pocket? Are they put in by the male? Does he feed them in there? Do they stay inside, or get in and out? Why does the female not have similar pockets?"

Yes, Sungrebe and the finfoots are mystery birds indeed.

Photos: The swimming Sungrebe Heliornis fulica was in the Brazilian Pantanal, in March 2007. Marc Fenner photographed his Sungrebe at Tortuguero, Costa Rica, in March 1991. Arthur Grosset photographed the African Finfoot Podica senegalensis in Ghana in May 2011.

      All photos © Don Roberson, except the photos credited © Marc Fenner and © Arthur Grosset, and used with permission; all rights reserved.

Many other fine photos of tropical birds are on Arthur Grosset's website

Bibliographic note: There is no "family book" but a fine introduction, with excellent photos, is in Bertrand (1996).

Literature cited:

Bertrand, B. C. R. 1996. Family Heliornithidae (Finfoots), pp. 210–216 in Handbook of the Birds of the World (del Hoyo, J., Elliott, A., & Sargatal, J., eds.). Vol. 3. Lynx Edicions, Barcelona.

Fain, M.G., C. Krajewski, and P. Houde. 2007. Phylogeny of "core Gruiformes" (Aves: Grues) and resolution of the Limpkin–Sungrebe problem. Molec. Phylog. Evol. 43: 515–529.

Hackett, S.J., R.T. Kimball, S. Reddy, R.C.K. Bowie, E. L. Braun, M. J. Braun, J.L. Chojnowski, W. A. Cox, K.-L. Han, J. Harshman, C.J. Huddleston, B.D. Marks, K.J. Miglia, W.S. Moore, F.H. Sheldon, D.W. Steadman, C. C. Witt, and T. Yuri. 2008. A phylogenomic study of birds reveals their evolutionary history. Science 320: 1763–1768