Kagus (Rhynochetidae)

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Kagus

(Rhynochetidae)

Class Aves

Order Gruiformes

Suborder Rhynocheti

Family Rhynochetidae

Thumbnail description
Medium-sized, agile, flightless birds with ash-gray and white plumage, orange-red legs and bill, dark-red eyes, long crest feathers, and black-and-white cross-banded wings

Size
Averages 22 in (55 cm); 2 lb (900 g)

Number of genera, species
1 genus; 1 species

Habitat
Forests and certain shrublands

Conservation status
Endangered

Distribution
New Caledonia

Evolution and systematics

Kagus (Rhynochetos jubatus) are rather oddballs among birds because they are a mixed bag of physical characteristics, some of which are unique to Rhynochetidae, but most of which are shared with other bird families. The name "Rhynochetos" refers to the unique rolled corns or nasal flaps that cover its nostrils. Kagus look like rails (Rallidae) and occupy a niche similar to Rallidae; however, kagus also exhibit light coloration and abundant, widely distributed powder-downs, much like herons (Ardeidae). Kagus have a unique blood composition compared to other bird species, consisting of one-third the number of red blood cells and three times the hemoglobin content. Early morphological comparisons correctly placed kagus in Gruiformes. Subsequent DNA and morphological comparisons by J. Cracraft and P. Houde et al. suggest that the kagu's closest living relative is the South American sun-bittern (Eurypygidae). These findings imply that the Rhynochetidae have an ancient, Gondwana origin.

Physical characteristics

Although flightless, kagus have large wings. They are medium-sized (1.5–2.4 lb [700–1,100 g]), quite compact, and agile birds that move surprisingly fast. Their dark-red eyes and orange-red, long legs and large bill contrast with their ash-gray and white plumage. A striking feature of the kagu's appearance, and usually concealed, is the patterning on the wings, which somewhat resembles that on the sunbittern's wings. The patterning consists of a dominant design of black-and-white cross-bands with a smaller area of brown "overlay" also running across the primaries. Their long crest feathers extend to the lower back and are difficult to spot unless raised. No secondary sexual dimorphism is known. The brown-and-fawn color of chicks gradually changes into a dull, adult-like plumage and is completely adult after about two to three years.

Distribution

Identified by Verreaux and Des Murs in 1860, kagus are endemic to New Caledonia where they live in only a small area of the mainland's forests.

Habitat

The main habitat for kagus is humid forest where the birds can find sufficient small invertebrates and reptiles in the soil

and litter and on low vegetation. Kagus also forage in more shrub-like vegetation if there is enough food available. Kagus have been reported foraging on beaches. In a 1991 survey, they were found at low altitude to over 4,600 ft (1,400 m) on New Caledonia's high peaks.

Behavior

Kagus are diurnal and roost at night, usually on low branches. In colder, winter conditions at higher altitudes, they mainly roost in natural shelters formed by rocks or tree roots. Kagus generally roost alone but sometimes do so next to partners and offspring, particularly in the breeding season. Preening is mostly carried out at the roost.

Mated pairs are territorial and defend areas of around 50 acres (20 ha) throughout the year. Although partners spend much of their day foraging and mostly alone, their first chore of the day is often to sing a distinctive duet. The male and female alternate in singing a sexually distinctive chorus that can be heard up to 1.2 mi (2 km) away. Some people liken this chorus to the yapping of a young dog.

In addition to their song, kagus are best known for their distinctive displays. For defense, the wings are opened to reveal their patterning and positioned forward-facing in an attention-grabbing display that might have acted to confuse past predators. This display is remarkably similar in form and function to the "frontal display" of the sunbittern. Kagus use a "strutting" display in courtship and in disputes with other birds. They take an upright pose with the crest raised and fanned and the wings held down and forward in the form of a cape. They then slowly circle around each other in a ballet-like dance. A captured bird held by the feet will also instinctively open its wings to reveal the patterning and bring them together as "shields" to cover its head.

Feeding ecology and diet

Kagus eat most types of small animal prey available to them. This behavior is consistent with the large amount of time they spend foraging and suggests that food is usually difficult to obtain. Prey includes a wide range of animals, like invertebrate larvae, amphipods, spiders, centipedes, orthoptera (e.g., crickets), cockroaches, millipedes, beetles, snails, worms, and lizards. Although they are generalists in the types of prey they eat, kagus seem to select larger, more rewarding food items when food supplies are abundant. Individuals have reportedly been seen catching small animals in shallow water. Kagus' unique nasal flaps may protect the nares when they forage in soil and water.

Kagus spend much of their foraging time motionless while trying to detect prey. They certainly use their relatively large, rather forward-facing eyes to notice prey movement, but they must also use other means, like vibration and/or sound, to pinpoint out-of-sight prey (e.g., in soil) that they capture. Once prey is detected, kagus spring into action and launch their bills into the likely spot where the prey is hidden. This foraging strategy results in characteristic "divets" in the soil made by birds digging with their bills. Food is most abundant for kagus during the summer wet-season storms from January to March.

Reproductive biology

Kagu pairs are monogamous and form long-term partnerships. Like many island birds that evolved with low predation, kagus have low rates of reproduction. They generally lay a single one-egg clutch each year. The breeding season is wellknown only at low altitudes, where the main nesting period is in the cool season from June to August, with most eggs laid

in July. This period is outside the time of peak food supplies, but wet season conditions may be unsuitable for nesting and birds molt in those months.

One-egg clutches are laid in simple, open-ground nests that sometimes involve nest-building using layered leaves. Incubation in the wild lasts 34–35 days and is shared by both sexes, who each take 24-hour shifts. Most chicks hatch with closed eyes and stay in the nest for the first few days. The chicks then gradually move away from the nest as they follow their parents.

Kagu parents are very attentive toward chicks and share feeding duties, bringing small prey to them. Both parents defend chicks aggressively and can also feign injury to draw an intruder away from the young. Chicks are brooded at night by one of the parents until they are about 6 weeks old, when they begin to perch. Parents feed the chicks for around 14 weeks until they become independent. Independent offspring can reside on their natal territories for many years before they establish their own territories, during which time they may assist their parents in protecting chicks. Males can start breeding around two years of age. Kagus can live for over 30 years in captivity.

Conservation status

Kagus are Endangered and listed in Appendix I of CITES. The species is fully protected in New Caledonia. The minimum number of kagus known in 1991 was 654 birds, including 163 in Parc Rivière Bleue reserve. The kagu population has declined because of habitat loss, introduced mammalian predators, and hunting and capture by humans. The main threat comes from roaming dogs who find the kagus to be easy prey. Wild pigs, cats, and rats also take a toll on the kagu population. Consequently, the unforgettable sound of many kagu pairs duetting in the early-morning dawn is absent from in most of New Caledonia's forests.

Local recovery efforts begun in 1977 have greatly increased the kagu's chances of survival. Kagus are bred in captivity and then released into Parc Rivière Bleue where some have successfully paired and raised young with wild partners. The number of birds in the Parc has increased substantially since the early 1980s due to predator control and the release of the captive-bred individuals under the guidance of Y. Létocart. Other kagus are mostly unprotected and at substantial risk

from predation. Another large kagu reserve is needed to ensure the species' survival over the long term.

Significance to humans

The kagu played a part in some indigenous Kanak cultures; for example, kagu feathers were worn by the chiefs and their song was used in war dances. However, kagus seem to have always been a source of meat for the Kanak people on an island where native terrestrial game was limited. Europeans continued the hunting and had a tradition of keeping kagus as pets, but this practice has ceased. Kagus hold a prominent place in New Caledonian national culture as a bird emblem and a unique tourist attraction.

Resources

Books

Houde, Peter, Alan Cooper, Elizabeth Leslie, Allan E. Strand, and Gabriel A. Montaño. "Phylogeny and Evolution of 12S rDNA in Gruiformes (Aves)." In Avian Molecular Evolution and Systematics, edited by David P. Mindell. San Diego: Academic Press, 1997

Hunt, Gavin R. "Rhynochetidae (Kagu)." In Handbook of the Birds of the World. Vol. 3, Hoatzin to Auks, edited by Josep del Hoyo, Andrew Elliott, and Jordi Sargatal. Barcelona: Lynx Edicions, 1996.

Thomas, Betsy T. "Eurypygidae (Sunbittern)." In Handbook of the Birds of the World. Vol. 3, Hoatzin to Auks, edited by Josep del Hoyo, Andrew Elliott, and Jordi Sargatal. Barcelona: Lynx Edicions, 1996.

Periodicals

Cracraft, Joel. "Gondwana Genesis." Natural History 110 (2001): 64–73.

Cracraft, Joel. "Phylogenetic Relationships and Trans-Atlantic Biogeography of some Gruiform Birds." Géobios. Mémoire spécial 6 (1982): 393–402.

Hunt, Gavin R. "Environmental Variables Associated with Population Patterns of the Kagu (Rhynochetos jubatus) of New Caledonia." Ibis 138 (1996): 778–785.

Hunt, Gavin R., Rod Hay, and Clare J. Veltman. "Multiple Kagu (Rhynochetos jubatus) Deaths caused by Dog Attacks at a High Altitude Study Site on Pic Ningua." Bird Conservation International 6 (1996): 295–306.

Létocart, Yves, and Michel Salas. "Spatial Organisation and Breeding of Kagu (Rhynochetos jubatus) in Rivière Bleue Park, New Caledonia." Emu 97 (1997): 97–107.

Livezey, Bradley C. "A Phylogenetic Analysis of the Gruiformes (Aves) Based on Morphological Characters, with an Emphasis on the Rails (Rallidae)." Proceedings of the Royal Society, London B 353 (1998): 2077–2151.

Organizations

Ligue pour la Protection des Oiseaux. La Corderie Royale, B.P. 263, 17305 Rochefort cedex, France. Phone: +33 546 821234. Fax: 33 546 839 586. E-mail: [email protected] Web site: <http://www.lpo-birdlife.asso.fr>