RAMPHASTIDAE TOUCANS FAUNA PARAGUAY

RAMPHASTIDAE - TOUCANS

Five species of this exclusively Neotropical family occur in Paraguay. The members of this family are so uniform morphologically that no subfamilial distinctions are recognised. Modern classifications have merged the Barbets (Capitonidae) into an extended Ramphastidae but this has gained little support. It can be determined however that the two families have a common ancestor dating from 10 million years ago. The oldest fossil toucans date back to the Pleistocene and the family is not well represented in the fossil record. The characteristics of the Paraguayan genera are discussed below.
Toucans are medium to large frugivores, though invertebrates are occasionally taken and many species predate bird nests. The bill is long, deep, often brightly-coloured and with forward-facing serrations along the tomia. Despite its size the bill is lightweight with little solid substance and filled with thin bony struts. The culmen is steeply downcurved and the gonys straight. The base of the bill has a thickened area around the sides of the nostrils, often appearing as a coloured vertical band along the bill base. This basal line and the serrations of the cutting edges are absent in juveniles. There is a large area of bare skin around the eyes which is often brightly-coloured and no bristles are present at the base of the bill. The tongue is extremely long, laminated along the sides and with a brush tip. Villi at the bases of downy feather barbules are much longer than in other bird families. Primaries are moulted outwards from P1 to P10 and secondaries inwards from P1 to P6 or P7 with an additional centrifugal moult starting at S8. Tail moult varies greatly between species but usually progresses both inwards and outwards simultaneously. The foot is zygodactyl with two toes pointing forwards and two backwards. The skull of toucan contains several unique features such as a distinctive palate with a short, truncate vomer and the nine tail vertebrae exhibit considerable modification. The terminal thee vertebrae are fused and articulate with the others via a ball and socket joint which allows the tail to be cocked up over the head - the roosting posture. The clavicles are separate. The oil gland is bi-lobed with a poorly-developed nipple. Toucans have an unusual tendency to store iron in the body and readily die from haematosis.
Flight of large toucans is undulating with several flaps followed by a glide. Smaller species have more direct flight with blurry flapping. All toucans are weak flyers and begin to lose height over large distances. Perched birds move by hopping, the bill being used to reach upwards and delicately pick fruits from thinner branches. Fruits are gripped in the tip of the bill and tossed back towards the oesophagous with a flick of the head. The bill may also be used in "fencing matches" between males design to decide dominance. Most species are social to some degree, but breeding takes place in monogamous pairs. Smaller toucans roost socially in tree holes, Ramphastos toucans roost side-by-side on branches of dense trees. Moutling birds scratch more often than non-moutling birds, passing the leg up over the wing to scratch the head. The bill is often wiped against a branch to clean it. Paired adults allopreen frequently and stretching and yawning is also common. Sunning occurs after rain, they bathe frequently and they may also pant for cooling purposes. In general they drink from arboreal water sources, holding the bill only slightly above the horizontal so that the liquid trickles towards the oesophagous. Courtship displays are not elaborate, typical of monogamous species that form lasting pair bonds.
Toucans nest in natural cavities, in Paraguay breeding from August to February. They are territorial and the presence of suitable cavities is a prerequisite for territory formation. Toucans do not excavate their own nests, preferring to use pre-existing cavities, but they may "clean" the cavity of excess material or rotten wood. The nest holes is defended against intruders and may be used in successive years. One to five white eggs are laid at daily intervals. The female incubates more than the male during the short incubation period of 15 to 18 days. Young are born blind, naked and with a long neck, calluses on the heels and a disproportionately long lower mandible. The nestling period is comparatively long, lasting 40 to 60 days depending on the species. The nest cavity is kept clean by the adults. No sexual dimorphism is present in the majority of species, but males tend to have the bill up to 10% longer than females. First breeding is at 2 or 3 years and some captive toucans have lived for over 20 years.

Selenidera (1 species) - Amongst the smallest of toucans. Iris with "glitches", dark areas of the iris in front of and behind the pupil giving a slit-like appearance to the eye. Distinctive musculature and sexual dimorphism in plumage. Alone or in pairs. Croaky calls and red under tail coverts used in display. Strictly forest dwellers.

Pteroglossus (2 species) - Medium-sized. Long, brightly-coloured bill hooked at the tip. Long, graduated tail. Confined to lowland forest. Yellow underparts. Sociable, with whistled calls. Saffron Toucanet sometimes separated into monotypic genus Baillonius on account of its distinctive plumage and proportionately longer tail.

Ramphastos (2 species) - Large, black above with coloured bibs. Long, deep-based bill. External nostrils hidden below bill base and brightly-coloured facial skin. Social. Emarginated, club-shaped tips to outer primaries. Croaking calls.

REFERENCES
Campbell B & Lack E 1985 - A Dictionary of Birds - T & AD Poyser.
Short LL & Horne JFM 2001 - Toucans, Barbets and Honeyguides - Oxford.
Short LL & Horne JFM 2002 - Ramphastidae Handbook of the Birds of the World Vol 7 - Lynx Ediciones.