Hornbill
Hornbills are celebrated for their large bill, often surmounted by a largecasque. They are conspicuous with their bold colors, varied calls and rushing wing-beats. Their biology is also remarkable, especially the unique breeding habits—the female seals herself into a nest hole for the entire nesting cycle.
Hornbills are an Old World group—unrelated to the toucans of the New World—with about half the species in Africa south of the Sahara (not Madagascar), half in southern Asia, and a single species extending to New Guinea. The larger forest species, most of which occur in Asia, are usually the largest avian fruit-eaters in their habitat and are probably important dispersers of the seeds of many forest tree species. More than half the African species inhabit savanna and woodland, especially the 15small Tocks species, which are mainly insectivorous, but also the two ground hornbills, which are among the larger avian predators.
The large bill characteristic of the family may be why hornbills are the only birds with the first two neck vertebrae (axis and atlas) fused together. The bill is long and down-curved, often with only the tips of the mandibles meeting properly, to form dexterous forceps. The cutting edges are often serrated for breaking up food. The casquesurmounting the bill is in its simplest form a narrow ridge that may reinforce the upper mandible. However, in many species thecasque is elaborated into a structure that is cylindrical, up curved, folded or inflated and sometimes exceeds the size of the bill itself.
The casqued is invariably poorly developed in young birds. In the adults of most species it is much larger and more elaborate inhales. In all but one species the structures a light skin of keratin overlying a bony support; it is probably used in recognizing the age, sex and species of an individual, as well as for amplifying calls in a few cases. However, in the largest Asian species, such as the Great and Rhinoceros hornbills, it may be used in fighting or to knock down fruit. Most remarkable is the Helmeted hornbill, with its straight, short bill support-in a casqued containing a block of solid keratin and together with the skull forming To percent of its body weight—possibly weighted digging tool.
The wings are broad and, in the larger species, produce a whooshing noise in flights air rushes through the base of the flight feathers (which lack underling coverts).The tail is long in most species, especially in the Long-tailed hornbill or the White-crested hornbill, while in the Helmeted hornbill the central pair of tail feathers is up to a meter (3.3ft) in length. In most species of the genus Rhyticeros the tail is short and pure white, and the ground hornbills also have short tails.
Notable colors and structures are found on the head and neck. The eye color may differ between species, or, between sexes assign the genus Boleros. Coloration of the bare skin around the eyes and on the throat may distinguish the species, sex or age of hornbill and in some species the throat skins inflated (ground hornbills, Rhyticeros, Aceros) or hangs as wattles (Ceratogymna).Hornbills are also notable for their long eye-lashes, and for the rather stubby legs and toes, with broad soles and the bases of the three front toes partly fused.
There is considerable evidence that hornbills are closely related to hoopoes and wood hoopoes in both their anatomyand their behavior. Hoopoes and the smallTockus hornbills that they most resemble are both primarily African groups, which sag-gests the source and basic form of their com-moon ancestor.
Hornbills in Africa, except ground hornbills, seem more closely related to each other than to those in the Oriental region. The large African species of Bycanistes (which have white rumps) and Ceratogymnaare unusual in that the head and neck of young birds and females are colored browning contrast to the black of males. In other-wise similar Oriental forms, such as Anthra-coceros. the young birds resemble males, assign most other hornbills, with brown heads being, confined to females in such genera asRhyticeros. Aceros and Penelopides. The smal-lest hornbills. In the genus Tockus, have diversified into 13 species in Africa, with further two similar but probably unrelated
Species in India and Sri Lanka, and the Long-tailed hornbill of Africa is very similar totem.
Among African hornbills only the ground hornbills are apparently allied to Oriental species, although this is far from obvious atfirst sight. The largest Oriental foresthornbills in the genus Buceros, togetherwith the specialized Helmeted hornbill, arederived from smaller Rhyticeros species.Some of these share with them the use ofpreen gland oils to color cosmetically thebill, casque and white areas of plumage withred, orange or yellow. However, only inBuceros species and the Helmeted hornbill isthe preen gland clothed in a special densetuft of feathers to improve the application,and this same special feature is found in theground hornbills of Africa. The ground hornbills are so different from otherhornbills in many aspects of their design andbiology that this difference may be discoun-ted were it not that they also share a specialgenus of feather lice with their Orientalrelatives.
The larger forest hornbills are mainlyfruit-eaters and most travel widely in searchof fruiting trees. The irregular fruiting anddispersal of the food source also mean thatthese species are not territorial and tend togather in large flocks in search of fruitingtrees. The birds use the long bill to reach outto fruits and toss each fruit back into the gullet, where the stubby tongue can assist theswallowing. Undigested remains, such aspips, are regurgitated or defecated, facilitat-ing seed dispersal.
Breeding hornbills have been observed toswallow as many as 69 small fruits andcarry them to the nest to be regurgitated forthe young. At one nest of a Silvery-cheekedhornbill it was estimated that the maledelivered 24,00o fruits, in the course of1,6o o nest visits spanning the 12o-daybreeding cycle. Any small items of animalfood are snapped up if encountered and inseveral species it appears that animal foodis specially sought during breeding, prob-ably as a source of extra protein for thegrowing young.
Most of the smaller hornbills are primarilyinsectivorous, taking other small animalsand some fruit when available, and most arealso sedentary and defend a permanent ter-ritory. However, some of the African specieswhich occupy seasonally dry savanna areforced to range widely once the rainy seasonhas passed. Exceptions to these two mainfeeding strategies are suspected for somelarge Oriental forest species, such as theWhite-crested and Helmeted hornbills,which are known to be sedentary—the former probably carefully searching thefoliage and forest floor for prey, and the lat-ter possibly excavating prey from rottenwood and loose bark. Only the very largeground hornbills are almost entirely car-nivorous, using their pickax-like bills to sub-due prey as large as hares, tortoises, snakesand squirrels, together with smaller farefound as they stride over the African veld.
Hornbills reach sexual maturity atbetween one (Tockus) and six (Bucorvus)years, depending on their size, but how longthey live in the wild is unknown. Breedingseasons depend mainly on the birds’ choiceof food, with forest fruit-eaters showing littleseasonality compared with savanna insec-tivores, which breed during the warm wetseason.
Courtship feeding of females, mutualpreening and copulation is all the activityreported to precede breeding in larger forestspecies. In many species the loud calls func-tion to proclaim defended territories, and insome the calls accompany conspicuous dis-plays. Territory size, in those non-fruit-eaters that do not just defend an areaimmediately around the nest, ranges fromioha (25 acres) for the Red-billed hornbillto ioosq km (39sq mi) for the Southernground hornbill.
Hornbills nest in natural cavities, usuallyin trees but also in rock faces and earthbanks. In all species but the two ground horn-bills, the female seals the nest entrance–apart from a narrow vertical slit—usingmud initially (while working from outside)but later her own droppings, mixed withfood remains. In some species the male
assists, by bringing lumps of mud or stickyfoods, and in a few, such as Byneanistes andCeratogymna, the male forms special pelletsof mud and saliva in his gullet and helps toapply these to the entrance. In some generathe male continues to feed the female andtheir offspring for the rest of the nestingcycle, while in others (Tockus, Buceros,Rhinoplax, Bycanistes, Ceratogymna,Rhyticeros, Aceros, Penelopides, Anthraco-ceros) the female breaks out of the nest whenthe chicks are about half grown and helpsto feed them. In the latter cases the chicksreseal the nest unaided and only break theirway out when ready to fly. The vertical slit,with the nest floor sited below it, providesgood air circulation through convection andthe small opening and wooden walls providegood insulation. The sealed nest, and thelong escape tunnel usually present above it,also provide protection from predators.
Food is brought to the nest either as singleitems held in the bill tip (eg Tockus,Tropieranus) or as a gullet-full of fruits whichare regurgitated one at a time and passedto the nestlings. Food remains and drop-pings are passed out of the nest slit, the latterbeing forcibly expelled. In most species thefemale undergoes a simultaneous molt of allher flight and tail feathers, which are drop-ped at the time of egg laying and regrownby the time she emerges. The groundhornbills are an exception to the basichornbill pattern ; the female does not seal thenest (although sitting throughout incuba-tion and the early nestling period, and beingfed in the nest), droppings and food remainsare not expelled and no unusual feathermolt occurs.
Most hornbills are monogamous, witheach member sharing all aspects of the nes-ting cycle. However, in some species, scat-tered through several genera, cooperativebreeding has developed in which someindividuals, usually males, although sex-ually mature, do not breed but help adominant pair to rear their young. Thishabit is recognizable by the birds living ingroups (of up to 25 in some species) and bythe immatures being colored very differentlyfrom the adults. it is found in species asdiverse in form and size as the Southernground hornbill, the White-crested hornbill,Bushy-crested hornbill, the Brown-backedhornbill and Philippine brown hornbill.
Several hornbill species have sufferedsevere reductions in their ranges, especiallyin Southeast Asia and West Africa. Others.such as the Narcondam hornbill. areendemic to small islands and hence alsovulnerable to alteration of habitat.
Toucans, HoneyGuides and Barbets
moco toucans are so often depicted by art-
ists and designers that they have becomea symbol of the warm forests of tropicalAmerica. Of all the rich bird life of theNeotropics, probably only hummingbirdsare more often illustrated.
The most prominent feature of toucansare their bills, often vividly colored, whichare much lighter in weight than theyappear. A thin horny outer sheath enclosesa hollow which is crisscrossed by many thin,bony, supporting rods. Despite this internalstrengthening, toucans’ bills are fragileand sometimes break. Nevertheless, somemanage to survive a long time with part oftheir bills conspicuously missing. The big-gest bill of any toucan is that of the maleToco toucan which accounts for 20CM ofthe bird’s total length of 66cm (8 of 26in).
Naturalists have speculated for centuriesabout the uses of the toucan’s exaggeratedbeak. It enables these heavy, rather clumsybirds to perch inside the crown of a tree,where branches are thicker, and reach faroutwards to pluck berries or seeds fromtwigs too thin to bear their weight. Seizedin the tip of the bill, food is thrown back intothe throat by an upward toss of the head.This behavior explains the bill’s length butnot its thickness or bright coloration. Thediet of toucans consists mainly of fruit butincludes insects, an occasional lizard andeggs and nestlings of smaller birds. Thehuge. vivid beak so intimidates distressedparents that not even the boldest of themdares to attack the plunderer perchingbeside its nest. After the toucan flies andis unable to defend its back in the air, anenraged parent may pounce upon it, towithdraw prudently before the larger birdalights. The varied patterns of toucans’bills may help these birds to recognizeeach other. In Central American forestsChestnut-mandibled and Keel-billed tou-cans have such similar plumage that theyare only readily distinguished by theirbills—and voices. The Keel-billed’s beak isdelicately tinted with all but one of the colorsof the rainbow, whereas that of its relativeis largely chestnut, with much yellow on theupper mandible. Possibly the bills also playa role in courtship.
Toucans are moderately gregarious andfly in straggling flocks, one after another,rather than in compact hands, like parrots.In flight, the big Rarnphastos toucans beattheir wings a number of times, then closethem, whereupon they lose altitude, asthough borne downward by their great,forwardly directed beaks. Immediately theblack wings are widely spread, the fall is converted into a short glide, followed bymore wing beats that recover the lostaltitude. Thus the toucan traces anundulatory course from one treetop toanother that is rarely far distant. Toucansprefer to remain high in trees, where theyhop from branch to branch. They bathe inpooh of rain water in hollows high in trunksand limbs—never, apparently, at groundlevel. They offer food to their companionsand, perching well apart, preen them withthe tips of long bills.
Toucans are playful birds and oftenengage in various games. After striking theirbills together, two clasp each other’s billsand push until one is forced backward fromthe perch and retreats. Another individualmay then cross bills with the winner, and
the victor in this bout may be challengedagain. Participants in such a wrestlingmatch reveal no sign of aggression. Inanother form of play, one toucan tosses afruit which another catches in the air, thenthrows it in similar fashion to a third, whomay pitch it to a fourth member of the flock.
Toucans arc often reported to sleep inholes, but this is only known to occur in themedium-sized aracaris and the Guianantoucanet
The big Ramphastos toucans appear tonest regularly in holes resulting from thedecay of tree trunks, the availability ofwhich may limit the number of breedingpairs. A favorable hole, in sound wood withan orifice just wide enough for the adults tosqueeze through, may be used year afteryear. The hole may be only a few cm or 2M(6.5ft) deep. A suitable cavity near the baseof a trunk may tempt toucans closer to theground than is normal. Smaller toucansoften occupy woodpeckers’ holes, some-times evicting the owners. They may cleanout and enlarge existing cavities, and some-times try to carve their own holes in soft,decaying wood, but apparently rarely withsuccess. The nest chamber is never lined,but the 2-4 white eggs rest upon a few chipsat the bottom, or upon a pebbly bed ofregurgitated seeds of various sizes, shapesand colors, which grows thicker as incuba-tion proceeds.
Parents share incubation and are, forbirds of their size, impatient sitters, rarelyremaining at their task for more than anhour and often leaving their eggs un-covered. Far from trying to repel intruderswith their great bills, the least threat causesthem to slip out and fly away.
After about 16 days of incubation thenestlings hatch blind and naked, with notrace of down on their pink skins. Like new-born woodpeckers, which they closelyresemble, they have short bills with thelower mandible slightly longer than theupper. Around each ankle joint is a pad ofspike-like projections, which protects it fromabrasion as the nestlings stand on theirrough floor, supporting themselves on heelsand swollen abdomen. Nestlings are fed byboth parents, with increasing quantities offruit as they grow older, but they developsurprisingly slowly. The feathers of the smalltoucanets do not begin to expand until theyare nearly four weeks old, and month-oldRarnphastos nestlings are still largely naked.Both parents brood the nestlings, sometimesthe male by night, as in woodpeckers. Theycarry large billfuls of waste from the nest.some, including Emerald toucanets, keepingthe nest perfectly clean, whereas Keel-billedtoucans permit decaying seeds to remain.
When finally fully feathered, young tou-cans resemble their parents, but their billsare smaller and less highly colored. Smalltoucanets may fly from the nest when 43days old, but the larger Ramphastos toucansremain for about 5o days. Aracaris are ledback to the nest to sleep with their parentshut, as far as is known, other fledglings roostamid foliage.
The biggest toucans, To species of thegenus Ramphastos, are chiefly inhabitants oflowland rain forests, from which they makeexcursions into neighboring clearings withscattered trees. They are rarely seen ataltitudes of 1, 50om (5 ,000ft) above sealevel. Their plumage is chiefly black orblackish and their calls are largely croaksand yelps, but the vesper song of theChestnut-mandibled toucan (dios to de,), isalmost melodious when heard in thedistance.
The r t species of aracaris are smaller andmore slender than the other toucans. Theytoo are inhabitants of warm forests, butrarely venture as high as 1,5oom (4,9ooft).They have black or dusky green backs, crim-son rumps and are usually black on headand neck. Their largely yellow underpartsare crossed by one or two bands of black orred. Their long bills are black and ivorywhite, wholly ivory white or mainly fieryred. Exceptional for this group, the Curl-crested aracari has its crown covered withbroad, shiny feathers that resemble curledhorny shavings. The calls of the better-known species are sharp and high-pitchedfor such large birds. They are the only tou-cans which, as far as is known, regularly lodge in holes throughout the year.
Toucanets of the genus Aulacorhynchus are small to large with mainly greenplumage. Their calls are unmelodiouscroaks, barks and dry rattles. They chieflyinhabit cool mountain forests, between1,000 and 3,000m (3,3oo—i 0,0ooft), andrarely descend into warm lowlands.
The five species of toucanets belonging tothe genus Selenidera dwell in rain forests atlow altitudes from Honduras to northeastArgentina. Their plumage is more variablethan that of the foregoing species, and theyare the only toucans of which the sexes differconspicuously in color. The reddish brown
bill of the Tawny-tufted toucanet is promi-nently striped with black. Little is known ofthe habits of these small toucans.
Least known of all are the four species ofmountain toucans which, as their genericname Andigena implies, inhabit the Andesfrom northwest Venezuela to Bolivia. Fromthe subtropical zone they extend far upwardinto the altitudinal temperate zone. Oneof the more colorful is the Black-billedmountain-toucan, whose light blue under-parts are exceptional in the toucan family.Its crown and nape are black. its back andwings olive brown, rump yellow, throatwhite, undertail coverts crimson and thighs chestnut. Although these and many othertoucans arc becoming rarer as their habitatsare destroyed. many remain to be studied bynaturalists hardy enough to pass longmonths in remote forests. APS
The dull plumage, remote habitat and retir-ing disposition of honeyguides disguise afamily whose behavior is among the mostextraordinary—and least known —of anybirds. They are named for the habit, of onespecies in particular (the Greater honey-guide), of guiding people and other largemammals to bees’ nests. Experiments havein fact shown that the birds prefer the bees’larvae and even their waxy comb to honey.Honeyguides combine two specializations :the unique one of eating wax and the lessunusual one of laying their eggs in otherbirds’ nests.
Honeyguides are probably most closelyrelated to woodpeckers and barbets. Theyoccur only in the Old World tropics, mostin Africa but two species in Asia. Their mainhabitat is broadleaved forest, though in twogenera (f’rodotiscus and Indicator) someinhabit more open woodland. Most of theAfrican species form several groups ofclosely related species which are so similarto each other that even specialists find themvery hard to identify, especially in the field. Within each group darker-colored speciestend to live in broadleaved forest, paler onesin drier woodland. So cryptic and incon-spicuous can they he that a totally new spe-cies was described from West Africa asrecently as t 98 .1 (Eisentraufs honeyguide).In most species the somber camouflage isrelieved only by light sides to the tail whichare conspicuous in flight and possibly helpto lure potential hosts away from their nests.Only three species depart from this drabuniformity: the Lyre-tailed honeyguide ofWest Africa, in which the tail of both sexesis curved outwards and the two pin-likeoutermost feathers make (like those ofsnipes) a loud tooting noise in diving flight;the Indian honeyguide of the Himalayas,which has orange on the head and rump ;and the Greater or Black-throated honey-guide in which the male has a black throat,white cheeks, yellow shoulder-flashes and apink bill, and which is the only species inwhich the sexes have a different appear-ance. All species have zygodactyl feet (ie feetin which the second and third toes of eachfoot point forward and the first and fourthbackward), like woodpeckers, and manyalso have curiously prominent nostrils,edged with a raised ridge; several speciesseem to he attracted to wood-smoke,perhaps especially to burning wax, and mayhave a keen sense of smell connected withlocating bees’ nests, though this intriguingpossibility has not been investigated.
All species, so far as is known, includewax of some kind in their diet, though mosteat mainly insects. Birds cannot digest waxwithout the aid of bacteria in their gut ; the
existence of these has been reported in Les-ser honeyguides but not confirmed in thisor any other species. Experiments haveshown that both Lesser and Greater honey-guides can certainly digest wax somehow,since they can survive on a diet of pure waxfor about 3o days. The small species in thegenus Prodotiscus eat mainly scale insects,which are thickly coated in wax.
Male Indian honeyguides defend bees’nests, at which they feed, and to whichfemales are admitted if they will mate. Thisspecies lacks white in the tail and may nothe parasitic, since females bring young tobees’ nests and their eggs have never beenfound despite searches of nests of likelyhosts. In several other species males givesimple monotonous calls from perches towhich females come to mate ; some speciesseem to defend possible hosts against otherhoneyguides. Honeyguide eggs are laid inholes in trees or banks, in the nests of otherspecies, almost always singly. Young of atleast two species hatch with sharp hooks onthe tip of the bill, with which they puncturehosts’ eggs or kill their chicks. They havean insistent begging call which sounds likeseveral of the host young calling together.
Honeyguides are birds of forest and wood-land, and their future is as threatened asthat of their habitat. The Greater honey-guide, with its unique mutually beneficial.relationship with man , must adaptto changing human behavior as well as toshrinking habitats if it is to survive. Awn
Any visitor to Africa is certain of hearing themonotonous repetitive calls of barbets as they occur in all the major vegetation zones ;5 African genera (39 species) are recognizedand within these there is a greaterdivergence in size, bill shape and color pat-tern than is found in Asian and Americangenera. Adaptation to more arid habitatswithin Africa is thought to have given riseto the tinkerbirds and ground barbets. Spe-cies equivalent to these ecologically do notoccur in Asia or tropical America. In thesecontinents the barbets are larger and in themain arboreal, 3 genera ( r 3 species) beingrecognized in South America and 3 genera(26 species) in Asia (where 2 genera containonly one species each). There are somenotable instances of convergence in thefamily. The Black-hacked barbet of CentralAfrica is similar to the White-mantled bar-bet of South America, and each continenthas a medium-sized brown plumaged spe-cies which is highly social.
Barbets are compact, thickset birds withrather large heads. The bill is stout, conicaland sharply tipped, being more formidablein the larger species. The Lybius species havenotched hills that assist in gripping food andin the Prong-billed barbet the tip of theupper mandible fits into a deep cleft in thelower mandible. Many have bristles aroundthe gape and chin and tufts over the nostrils.The legs are short and strong, the feetzygodactylic (ie on each foot the second andthird toes point forward, the first and fourthbackward). They climb like woodpeckersand their short tail is often used as a support.The large barbets appear heavy and cum-bersome in their movements but others (egthe Red-headed barbet and the tinkerbirds)are agile and probe and search much liketits. The wings are short and rounded, andunsuitable for sustained flight. Ground bar-bets move by inelegant hops.
The Eubucco species of South Americahave green wings, back and tail, and under-parts of yellow streaked with green. Theydiffer from each other in the color patternof their head, throat and breast; the sexeshave different appearances. The male Red-headed barbet has the whole head andthroat scarlet shading to orange on thebreast, and a blue collar on the nape. Thefemale has blue on the side of the head, agray throat and yellow orange on the upperbreast. The sexes of the Capito species arealso different. Both sexes of the Black-spotted barbet have scarlet on head andthroat, black upperparts streaked withgreenish yellow and creamy yellow under-parts. The female differs from the male inhaving black spots on the throat and beingmore heavily spotted black on the under-
parts. Most Asian barbets are pre-dominantly green and differences betweenspecies lie in the head colors (brown, red,yellow, orange) and their pattern ; the sexesare identical in the field. The Great barbethas a yellow bill, maroon-brown upper-parts, a violet blue-black head, multicoloredunderparts (olive brown, blue, yellow) andred under-tail coverts. In contrast, there isvery little green in African barbets, and themajority are patterned black, yellow and redand their plumage is heavily spotted andbarred, much more so than in Asian andSouth American species. Some are a verydrab brown (Gymnobucco species) and havea tuft of’ rictal bristles and a head more orless bare of feathers. The sexes are alike inthe majority of species.
Most species feed on fruit, much of whichis lost when plucked from the tree, but someare more efficient and hold the fruit with afoot when eating. Petals, flower heads andnectar are eaten by some species (for exam-ple, the Great barbet, Prong-billed barbet).Most, if not all, species feed insects to newlyhatched young and some take insectsregularly, particularly termites which maybe caught either on the wing or on theground. Ants and grasshoppers are takenand the larger species (for example, theLineated barbet) occasionally take lizards,tree frogs and small birds. The Red-headedbarbet is mainly insectivorous and feeds inthe ground litter. Insect remains areregurgitated as pellets. Fruit-eating barbetsoften feed in mixed flocks of other species.There are no seasonal migrations ; local movements are governed by the availabilityof food sources.
The breeding behavior of barbets is variedbut little studied. The Prong-billed barbet inCosta Rica lays only one clutch of eggs andhas a restricted breeding season beginningin March. Other species are paired through-out the year and have a prolonged breedingseason covering both dry and wet seasonsin which three or four broods may be raised(for example, the Yellow-fronted tinkerbird)or else breed only in the wet season (forexample, ground barbets). The same hole isoften used for successive broods and isdeepened after each brood. D’Arnaud’s bar-bet, one of the ground barbets, bores a tun-nel vertically downwards into level groundand then bores horizontally before formingthe nest chamber. The Pied barbet has beenknown to use deserted nests of swallows andmartins when nest-sites are scarce. Bothsexes excavate the nest-hole, share inincubation and feeding nestlings, and innest sanitation. Feces are sometimes swal-lowed or else pounded with sawdust in thenest-hole into small halls which are thenremoved. In several of the African speciesextra helpers, often young of a previousbrood, have been recorded feeding nestlingsbut little detail is known of the cooperativebreeding. The African Gyrimobucco speciesbreed colonially and with other African spe-cies are often parasitized by honeyguides.
Because of the difficulty of observing bar-bets, particularly the forest species, little isknown of their courtship behavior, only thatthe male frequently pursues the female. Inground barbets the male postures withraised crown feathers and struts around thefemale. Duetting is a common feature of bar-bets from all three continents. Its exact func-tion is not certain. It occurs throughout theyear and there is an immediate response bybirds to the play-back of a duet sequence.It probably helps to maintain both territoriesand family bonds. Barbets are highly ter-ritorial and aggressive to other birds (egwoodpeckers, honeyguides) and may thenhe defending a food source (fruit) or a roost-ing or nest site. Communal roosting offamily parties is frequent, even in aggressivespecies.
The metallic quality of the voices ofseveral African and Oriental species hasearned them names such as stinkerbird.blacksmith and coppersmith.
The young hatch blind and naked andhave heel pads. These may be used toenlarge the cramped nest-hole : the honey-guides that are parasitic on barbets alsohave the pads.