Plantcutters (Phytotomidae)

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Plantcutters

(Phytotomidae)

Class Aves

Order Passeriformes

Suborder Tyranni (Suboscines)

Family Phytotomidae

Thumbnail description
Small, herbivorous, finchlike birds with serrated bills for cutting plant material

Size
Approximately 7 in (17–20 cm), 1.5 oz (40 g)

Number of genera, species
1 genus, 3 species

Habitat
Forest, scrubland, and desert

Conservation status
Endangered: 1 species

Distribution
Central temperate to subtropical South America, from Peru and Bolivia to Chile, Uruguay, and Argentina

Evolution and systematics

The issue has not been settled as to whether the suboscine Phytotomidae represent a distinct family or a genus within the family Cotingidae. Lanyon and Lanyon consider the Phytotomidae a genus (Phytotoma) within the family Cotingidae. Prum and colleagues provisionally place the plantcutters as a subfamily (Phytotominae) within family Cotingidae. Sibley and Monroe list the plantcutters as genus Phytotoma in their subfamily Cotinginae within the family Tyrannidae. Most ornithologists recognize a distinct family Cotingidae.

In any case, the plantcutters are most closely related to the tyrants and becards (family Tyrannidae), cotingas (Cotingidae), sharpbills (Oxyruncidae), and manakins (Pipridae). All are New World suboscine families.

There are three species of plantcutter: the Peruvian plantcutter (Phytotoma raimondii), the red-breasted (or white-tailed) plantcutter (Phytotoma rutila), and the rufous-tailed plantcutter (Phytotoma rara).

There is no reliable fossil evidence of Phytotomidae ancestry.

Physical characteristics

Plantcutters (in South America, also called cortarramas, cortaplantas, and raras) look at first glance like rather ordinary, finchlike birds with a few exotic splashes of red applied to mostly gray or brown plumage. Head plumage rises to a short crest in the Peruvian and red-breasted plantcutters. Individuals are about 7 in (18–20 cm) long and weigh about 1.5 oz (40 g). They are short-crested and have short, stout, conical bills. The wings are short and pointed, the tail long, and the legs short with large, strong feet.

The sexes show considerable dichromatism. Males are more brightly colored, especially with reds, while females are more grayish to brownish.

A close look at the plantcutter bill reveals a feature rarely seen among birds: rows of tiny, strong, sharp, toothlike projections run the lengths of the tomae, or bill edges, on both sides of each mandible. These are not bony teeth but, rather, outgrowths of the keratin substance of the bill. The birds use these bills to saw through and to chew leafy vegetation, their main food source. Peering at a close-up photograph of the head, with the rows of sharp, forward-leaning pseudo-teeth, accentuated by the glaring red or golden eye, is more like coming face to face with a dragon than with a small, herbivorous bird.

Distribution

The Peruvian plantcutter is endemic to the dry scrublands of northwestern Peru. The rufous-tailed and red-breasted plantcutters live from temperate southern Argentina and Chile, northward to subtropical Paraguay and Bolivia.

Habitat

The Peruvian plantcutter lives in near-desert conditions. The rufous-tailed and red-breasted plantcutters prefer a mix of open forest, scrubland, grassland, and farmland.

Behavior

Herbivory is a rare lifestyle among birds. Herbivorous birds tend to be rather passive and slow-moving. Plantcutters, however, are lively and energetic. They are also quite capable flyers, patrolling their areas throughout daylight hours for food.

Feeding ecology and diet

Very few bird species subsist mainly on leaves as a food source. Those that do usually pay a significant price because of the high fiber content and diluted energy availability of leafy foods. The trade-offs may involve larger size, flightlessness, and low activity to conserve energy. There may also be elaborate modifications of the digestive tract. The New Zealand takahe (Porphyrio mantelli), whose dietary mainstay is alpine tussock grasses, is flightless. It has an inefficient digestive system and must eat almost continuously during its waking hours to ensure adequate nutrition. The leaf-eating hoatzins (Opisthocomus hoazin) of tropical South America lodge passively in dense riverside thickets for safety and are poor fliers. Their crops are enlarged, having become extra stomachs full of symbiotic bacteria able to digest the tough, fibrous cell walls of leaf tissues.

The plantcutters, though, seem not to have paid a high price for their choice of diet. The secret lies in the species' feeding methods and digestive system. Chilean biologists recently undertook several studies of food intake and processing in the rufous-tailed plantcutter. Data support the efficiency of the bird's feeding and digestion, and this likely applies to the other plantcutter species. Plantcutters chew their leafy food into a pulp to rupture the tough plant cell walls and free the nutritious cell interiors for digestion. Food passes rapidly through the digestive system, which has little in the way of elaboration (although the intestine is abundantly supplied with mucous cells along its length, concentrating them toward its nether end). This combination of chewing, rapid passage of food through the digestive system, and efficient digestion allow the bird to process hefty amounts of plant material over shorter times and thereby maintain a high metabolic level.

Plantcutters spice up their diets with some intake of fruits and insects, but leaves of many plant species, depending on availability and type of habitat, are the mainstay. Rufous-tailed plantcutters have developed an affinity for cereal leaves, among them wheat and oat.

Reproductive biology

Little is known about reproduction in the Phytotomidae, mostly due to a lack of field studies. The birds build loose nests, and the females lay up to four eggs.

Conservation status

One species, the Peruvian plantcutter, is Endangered due to loss of numbers and habitat. The other species are more widespread and are not threatened.

Significance to humans

Plantcutters at times make nuisances of themselves by raiding farms and vineyards to feed on young leaves of cereal crops and grapevines. The Peruvian plantcutter has a limited distribution and is relatively easy to observe. It thus attracts birdwatchers from all over the world who wish to see this unusual and now endangered species. This generates some modest local income and gives conservationists another good reason to push for protective measures for the species. The Peruvian plantcutter has become a rallying symbol for conservation.

Species accounts

List of Species

Peruvian plantcutter
Rufous-tailed plantcutter

Peruvian plantcutter

Phytotoma raimondii

taxonomy

Phytotoma raimondii Taczanowski, 1883.

other common names

French: Rara du Pérou German: Graubrust-Pflanzenmäher; Spanish: Cortaplantas Peruana.

physical characteristics

7–8 in (18–20 cm) long, about 1.5 oz (40 g). Both sexes are mainly medium gray, with bright yellow eyes and a cardinal-like crest. The male adds red patches on the forehead and lower breast.

distribution

A wide area around the northern town of Talara, some small forests near Chiclayo (south of Talara), and a small forest farther south from Chiclayo; total known population estimated at 500–1,000, with perhaps 80% in the habitat around Talara.

habitat

Dry scrubland vegetation with bushes widely dispersed; part of the Tumbesian ecosystem.

behavior

Diurnal; the call has been described as a donkeylike braying or like the movement of a rusty hinge; little specific information, due to lack of thorough field studies.

feeding ecology and diet

Follows the general description for plantcutters, although Peruvian plantcutters consume leaves from wild plants and have no known liking for cereal leaves. The birds will eat leaves of the widespread algarrobo (Prosopis spp.), chilco (Baccharis spp.), zapote (Maytenia spp.), and vichayo broadleaf bush.

reproductive biology

Almost nothing is known, due to lack of field observations.

conservation status

Endangered. In 1992 Peruvian plantcutters could be found in 14 sites along the north Peruvian coast; in 1998 Engblom revisited these sites but found plantcutters at only three. He then found three new sites southward.

Never very widespread, the Peruvian plantcutter is adapted to the native arid scrub forest of northwestern Peru, most of which has nearly disappeared or been degraded by goat grazing, extraction of firewood and timber, and conversion of land to sugarcane fields. The long-term security of the species will depend primarily on protecting its stronghold in the Talara region. To this end the Peruvian organization ProAves Peru, partly funded

by the U.S. National Audubon Society, is working toward the declaration of a reserve, environmental education at the local level, and restoration of plantcutter-friendly habitat.

significance to humans

The Peruvian plantcutter has become a rallying symbol for conservation.

Rufous-tailed plantcutter

Phytotoma rara

taxonomy

Phytotoma rara Molina, 1782.

other common names

English: Chilean plantcutter; French: Rara à queue rousse; German: Rotschwanz-Pflanzenmäher; Spanish: Cortaplantas Chileno.

physical characteristics

Considerable sexual dichromatism; the gaudy male outshines the more muted female. Weight about 1.5 oz (48 g), body length about 7 in (17 cm). The male shows reddish on the crown, throat, breast, and underparts. The back of the neck and dorsal plumage are dark olive green, with darker stripes. The blackish wings bear a distinctive white stripe. The tail is mainly blackish, with a red stripe down its middle. The female tends to muted browns, shading to grayish. The breast and abdomen are

whitish with dark, longitudinal streaks in the breast and flanks. The wings are blackish like the male's, but lack the white stripe. The eyes are a vivid, emphatic red in both sexes.

distribution

Chile and Argentina, from Vallenar in the north to Chiloe in the south, and into Chilean and Argentinean Patagonia.

habitat

Forest, scrublands, and farmland from sea level to 6,000 ft (2,000 m) above sea level.

behavior

Little has been recorded of the bird's daily activities, aside from what is described in the feeding ecology.

feeding ecology and diet

The species often lives near farms because of its special fondness for young cereal leaves, although leaves of native plants will also be eaten. During the austral summer, the bird adds fruit and insects to the leaf diet.

reproductive biology

The species prefers to nest in the forks of tree branches, but will nest in higher shrubs. The nest is made with root fibers and large twigs on the outside and smaller twigs inside. Brooding takes place in the austral summer. Egg-laying begins in October and produces two to four eggs of a clear bluish green color with some blackish spots.

conservation status

Not threatened, although uncommon.

significance to humans

The rufous-tailed plantcutter can be a nuisance to farmers because of its fondness for cereal leaves.

Resources

Books

Best, Brinley J., and Michael Kessler. Biodiversity and Conservation in Tumbesian Ecuador and Peru. Cambridge: Birdlife International Publications, 1995.

de la Pena, Martin R., and Maurice Rumboll. Guide to the Birds of Southern South America and Antarctica. Princeton: Princeton University Press, 1998.

Feduccia, Allan. The Origin and Evolution of Birds. New Haven: Yale University Press, 1999.

Ridgely, Robert S., and Guy Tudor. The Birds of South America. vol. II, The Suboscine Passerines. Austin: University of Texas Press, 1994.

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

Periodicals

Lanyon, S. M., and W. E. Lanyon. "The Systematic Position of the Plantcutters, Phytotoma." Auk 106 (1989): 422–432.

Lopez-Calleja, M. V., and F. Bozinovic. "Energetics and Nutritional Ecology of Small Herbivorous Birds." Revista Chilena de Historia Natural 73 (September 2000): 411–420.

Lopez-Calleja, M. V. and F. Bozinovic. "Feeding Behavior and Assimilation Efficiency of the Rufous-Tailed Plantcutter: A Small Avian Herbivore." Condor 101 (August 1999): 705–710.

Meynard, C., M. V. Lopez-Calleja, and F. Bozinovic. "Digestive Enzymes of a Small Avian Herbivore, the Rufous-Tailed Plantcutter." Condor 101 (November 1999): 904–907.

Prum, R. O., N. H. Rice, J. A. Mobley, and W. W. Dimmick. "A Preliminary Phylogenetic Hypothesis for the Cotingas (Cotingidae) Based on Mitochondrial DNA." Auk 117(2000).