GALBULIDAE JACAMARS FAUNA PARAGUAY

GALBULIDAE - JACAMARS

Only one species of this exclusively Neotropical family reaches Paraguay, the extreme northern Chaco representing the southern limits of the family´s range. The first Jacamars were described as Kingfishers (Alcedinidae), but the distinctiveness of the family was recognised by Bonaparte in 1850. Today Jacamars are considered closest to the Puffbirds (Bucconidae) in the order Galbuliformes, restoring them to a position that original taxonomists first proposed despite several changes in the intervening decades. Previous arrangements included them within the Piciformes on the basis of hind limb morphology and perceived similarities in skeletal and muscular structure. Numerous features are also shared with the Coraciiformes, not least the desmognathous palate, aspects of mandibular musculature, cranial osteology and tongue physiology. Egg-white protein analyses suggest a closer relationship to Kingfishers than to Woodpeckers (Picidae). They differ from Puffbirds through various minor features of muscle and bone design and in the fact that they have subdivided, single-shafted barbs on the aftershaft of the contour feathers. The species are weakly-differentiated suggesting a recent radiation from a small number of ancestral species during the Pleistocene.
Jacamars have a long, straight, thin bill. This has been postulated to have three advantages, keeping stinging insects away from the head, allowing the bird to grip the body of long-winged insects to avoid prey loss and tips of longer bills can be closed faster allowing them to catch fast-moving prey. The plumage is glossy and sleek. Overall they are slender with a small head and because of their habit of holding the bill angled slightly upwards they may superficially resemble giant Hummingbirds (Trochilidae). A similarity to Old World Bee-eaters (Meropidae) reflects convergent evolution as a result of similar lifestyles rather than a taxonomic relationship. The oil gland is naked. The long tongue (c25mm in the Paraguayan species) is thin, flat and simple with a distinct median groove on the dorsal side. The nostrils are pronounced, opening at the base of the bill and behind emerge a series of stiff, forward-facing bristles. The head has a sloping profile. Cranially the vomer is absent and postorbital process long. There are 14 cervical and 5 dorsal vertebrae, 2 cervical ribs and 5 pairs of true ribs. Wings are short and rounded with 10 primaries (the outermost short) and 12 secondaries. The tail is generally long and graduated, providing increased aerial maneuverability. There are 12 retrices, the outermost being shortest. Primary moult is simple and descendant in centrufugial sequence. Secondary and tail moult are irregular. Legs are short and weak, scutellated anteriorly and smooth posteriorly. The feet are zygodactyl with digits 2 and 3 forward-facing and 1 and 4 backward-facing. The forward-facing digits are joined along half of their length (syndactyl), possibly of use in nest excavation. The gizzard is muscular and there is no gall bladder. Intestine is short with capacious caeca. The flesh is reported to have a strong and unpleasant odour.
Jacamars are principally arboreal and associated with edges of wooded habitats. The presence of banks for nesting is also likely important. They are diurnal and conspicuous in behaviour, sitting still for prolonged periods with constant side to side movements of the head in search of prey and repeated foraging flights before returning to a perch. Such flights are swift and darting, but over longer distances (for example when changing perch) flight may be interspersed with short glides. Head-scratching is performed by bringing the leg over the wing and the bill may be wiped against a branch to clean it. Jacamars also occasionally take dust baths. Roosting is in burrows, but it is unclear if the same burrows are used for nesting as for roosting - in some cases it seems that it is not. Adults defend small foraging territories in the vicinity of the nest. Both sexes defend the territory but defence is usually in the form of singing and short chases, actual physical aggression is rare. High call notes are given throughout the day, as well as rapid trills and other complex vocalisations reminiscent of passerines. Even nestlings are capable of these complex "songs". Birds in the hand snap the mandibles together. Jacamaras are exclusively insectivorous in diet, taking prey with an audible snap of the bill. They favour Lepidoptera, Odonata, Hymenoptera, Diptera, Coleoptera and Hemiptera and only take prey in flight, ignoring stationary prey items. The success rate in wild birds is c60% and prey is beaten on a branch to remove its wings before being eaten. Pellets of indigestible material are regurgitated at intervals.
The Paraguayan representative of the family is monogamous. Courtship involves bouts of male singing and ritualistic feeding. The nest is a burrow dug into soft substrate - it would seem that the presence of a perch that allows direct access to the nest if of importance in choosing suitable sites. The bill is used to loosen soil which is then kicked away with the feet. Both sexes excavate although the greater part of the burden is borne by the female. During excavation the male frequently feeds his hard-working mate. Nest chambers are long, narrow, straight and it is often suggested that they have a rectangular entrance - though whether that is always the case needs to be confirmed. The nest chamber quickly becomes filled with feces and regurgitated chitinous remains of foodstuffs. The eggs are shiny, almost spherical and are incubated by both sexes for 19-26 days. Hatchlings are covered in white down, longest on the chin where it gives a "bearded" appearance. They are born blind with the lower mandible protruding beyond the upper. The toes all point forwards on hatching, the first and fourth digits rotating backwards to form the zygodactyl foot by the end of the first 6 days. A smooth callous is present on the tarsus. Fledging takes around 20-26 days. There are only minor sexual differences in plumages (principally throat colour) and no clearly-defined juvenile plumage making ageing and sexing difficult.

REFERENCES
Campbell B & Lack E 1985 - A Dictionary of Birds - T & AD Poyser.
Tobias JA 2002 - Galbulidae Handbook of the Birds of the World Vol 7 - Lynx Ediciones.