BUCCONIDAE PUFFBIRDS FAUNA PARAGUAY

BUCCONIDAE - PUFFBIRDS

Four species of this exclusively Neotropical family occur in Paraguay. The origin of the family name is uncertain, but may refer to the large bill or perhaps the perceived stupidity of these birds. The English common name refers to the loose plumage which is often puffed out when the bird is resting. A number of fossil species once though to belong to this family have now been classified elsewhere, including a related but extinct family Primobucconidae which dominated in North America during the Lower and Middle Eocene. The family is currently considered to be unrepresented in the fossil record. Early taxonomists classified the Puffbirds with the Barbets (Capitonidae), and the spinal cord is reminiscent of the Piciformes but they are today placed in the order Galbuliformes jointly with the Jacamars (Galbulidae) with which they share numerous aspects of osteology, myology and syringeal and hyoid morphology. Furthermore both groups possess an aftershaft, though it is vestigial in the Puffbirds. This arrangement is supported by DNA-DNA hybridisation analysis and egg-white protein analysis. There are no subfamilial distinctions currently recognised in the Bucconidae. The main characteristics of the genera represented in Paraguay are given below.
Bucconids have large heads and large eyes. The slightly binocular eyes give high resolution vision even in poor light and allow foraging to continue even after dark. The bill is broad, chunky and hook-tipped, a series of forward-facing bristles are arranged at its base. Nostrils have a large operculum. Wings short and rounded, tail of short to medium-length, narrow and graduated. Primary moult follows a descendant centrifugial sequence, secondary and tail moult being irregular. The plumage is lax and generally dull-coloured. Puffbirds have eyelashes, a naked bilobed uropygial gland, posteriorly scutellated tarsi and non-oscinine wing-coverts. The small feet are zygodactyl with digits 1 and 4 reversed. Skeletally Puffbirds possess a vomer, a rounded gonys, a high keel on the palatine, and a desmognathous palate. Like the Jacamars they lack ectepicondylar processes on the humeri. The quadrate has a short, broad, pointed orbital process, the medial condyle is deep, terminating in a rounded tubercle and the postorbital process is long, curved and broad. There are 14 cervical and 4 dorsal vertebrae, 2 cervical and 4 true ribs. Internally the caecae are long and globose, the gizzard is muscular and thick-walled, there is no gall bladder and they have two carotids. Body temperature is lower than in most passerines and members of the genus Nystalus have been recorded to enter into states of torpor during times of cold weather. Age-related plumage differences are minimal in most species, but juveniles generally show duller bare parts. There is no sexual dimorphism amongst Paraguayan species.
Flight is direct and fast on blurry wings. Perhaps because of the strong ribs, Bucconids show extraordinary resistance to shooting and attempts to kill them by thoracic compression. Indeed some species will even fake death upon capture, only to come to life again later. The flesh is reported to have an unpleasant odour. Puffbirds are arboreal in behaviour, though they may drop to the ground to take prey occasionally and some species nest underground. Most species are found in forest edge habitats where they are territorial year round and sedentary. They perch erect or semi-erect with the tail pointing vertically downwards. Perched birds make slow side-to-side head movements in search of prey. Prior to taking flight and when singing they may pump the tail or move it side-to-side. Sociable species roost together. They scratch the head by bringing the leg up over the wing. The diet is insectivorous, most prey being taken from sally-strikes against vegetation before returning to a perch - in the manner of a flycatcher. Prey is beaten against the perch before being swallowed.
Puffbirds are monogamous breeders and cavity nesters - both sexes helping to excavate the nest holes. Eggs are small, white and dull to glossy. A single brood is raised per year, but lost clutches may be replaced. Both sexes share the task of incubation, but after hatching the male does most of the brooding whilst the female is charged with food provision. Hatchlings are naked, blind and pink, but though they appear altricial they are capable of considerable movement. Fledging takes c20 days.

Nystalus (2 species) - Non-bifid bill tip or tip slightly bifid. Brightly-coloured bill and barred tail. Social with complex vocalisations involving duets and choruses. Nest in underground burrow. Inhabit more open and even dry areas.

Notharchus (1 species) - Pied plumage. Bifid bill tip. Nest in arboreal termitaria.Humid forest only.

Nonnula (1 species) - Small with drab, unstreaked and unspotted plumage. Long, thin bill with silvery sides. Conspicuous bare eye-ring. Simple, whistled, monotonous calls. Solitary. Nest in arboreal termitaria or in the ground. Humid forest only.

REFERENCES
Campbell B & Lack E 1985 - A Dictionary of Birds - T & AD Poyser.
Rasmussen PC & Collar NJ 2002 - Bucconidae Handbook of the Birds of the World Vol 7 - Lynx Ediciones.