Broadbills
Broad Bills are sturdy birds whose squat appearance is accentuated by a rathershort, square tail, except in the Long-tailedbroadbill which has a fine-pointed tail. Thefamily is named fbr the great width of themouth, which reaches a grotesque extremeamong passerines in the outsize pink bill ofthe Dusky broadbill. Broadbills inhabitchiefly the interior of evergreen or semiever-green broad-leaved lowland forest. Only twospecies are exclusive mountain dwellersalthough Long-tailed and Silver-breastedbroadhills are restricted to mountainsides in.inner tropical Southeast Asia.
No genus is common to both areas of thebroadhills’ distribution and the diminutive,mainly brown, ventrally streaked Black-capped, Rufous-sided and Cray-headedbroadbills look so different from their gaudyAsian relatives that they were long classifiedas flycatchers- -shape of bill not withstand-ing. Anatomical studies exposed thisapparent error, adding broadhills to the Afri-can bird stock in 1914 though 19 moreyears elapsed before the discovery of theAfrican green broadbill. Three genera aregreen with black, blue or yellow on thehead, wings, belly or tail. Long-tailed, Hose’sand occasional male Green broadhills haveall of these colors. The Banded broadbill iswine-red with a blue bill, and other speciesare black with areas of red, lilac, yellow and/or white. Black is replaced by rich chestnutin the Philippine broadbill.
For all their color, however, brightplumages are not especially conspicuous inforest and the most prominent feature of, for
example, the Black-and-red broadbill, sit-ting in th.e shade of a waterside thicket, isits almost luminous pale blue and yellow bill(which fades after death and cannot beappreciated in museum specimens). Severalspecies, including those of the genusSrnithorrris, also have on their backs one ormore white, yellow or orange flashes on adark background, exposed during flight, andSilver-breasted broadhills have a brightchestnut rump, often fluffed out when theyperch.
In most species the bill is both wide androunded along its sides, perhaps to aid theaerial capture of large arthropods by ratherslow-moving birds. It is also variouslyhooked, almost hawklike in the Duskybroadbill which has been seen snatching bigorthopterans in an upward leap from theperch. This bill-form is otherwise found onlyin trogons and frogmouths, which share thebroadbill habitat and feed similarly. Otherforaging modes include “flutter-snatching”from foliage and hark, and a Banded broad-bill is recorded capturing a lizard. Most spe-cies forage at mid levels of the forest but theDusky broadbill is a high canopy bird. Twoothers, the Black-capped in Africa andBlack-and-red in Asia, inhabit forest edgeand thickets, and will go to the ground tofeed. Besides taking insects in their water-side habitat, Black-and-red broadbills some-times also capture aquatic organisms.
The African green broadbill and Calyp-tomena species alone have hills that arestraight-sided but still very wide at the base.The latter feed largely on fruit and while these two genera are not necessarily closelyrelated there is evidence that the Africangreen broadbill also takes much plantmaterial.
Green broadbills often advertise theirpresence by cooing rattles, and pairs willdrive members of the same species off small,defendable fruit sources. At larger sourcesseveral may gather, as will Hose’s broad-bills. These two live mainly in lowland fore-sts where fruit is scattered and like otherfruit-eating birds they must wander over asizable area if they are to find sufficient food.Green broadbills even disperse at night.Their much larger relative, Whitehead’sbroadbill, lives exclusively above 200 m
(4,000ft) in montane forest where fruit sup-plies may be more stable.
Insect-eating broadbills are more seden-tary. Banded and Black-and-yellow broad-bills space themselves through the forest.Their presence is advertised with loud,explosive trilling calls, invariably answeredby neighbors. Most others are lessvociferous. Smithornis species are peculiar inproducing a nonvocal croaking noise,apparently during short, circular flights.This sound is produced by vibrating wings.These flights are thought to have a court-ship function but the noise produced by theBlack-capped broadbill carries up to 6om(about 20(.)ft) and could also be a territorialsignal. Most species give a clear two-syllablewhistle, most often when foraging groupsassemble after breeding. These groups areusually small but as many as 20 Silver-breasted broadbills may gather and up to 26Long-tailed broadbills have been countedprogressing together through mountainforest in North Sumatra. Only the Duskybroadbill is permanently gregarious, andoccurs in noisy parties of up to To strong.
Broadbill nests are large, pear-shapedbags with a crudely overhung side entrance,slung by a long woven cord of nest materialfrom an isolated branch, creeper or frond-tip. They are roughly made, of all kinds ofvegetation, drawn out below into a wispyheard. Leafy creeper, lichen and moss andleafy liverworts are often included and it iscommon for the nest chamber to be linedwith fresh green leaves. Usual nest-sites arewell off the ground but the Green broadbill,whose nest is broadly strapped over its sup-port, invariably builds low, as do Smithornisspecies. Black-and-red broadbills often use adead stump or snag in a stream, and willsometimes take advantage of a service wireover a stream or road. There are no recordsof helpers attending broadbill nestlings, butthe Dusky broadbill flock cooperates in nestconstruction. In Malaya Black-and-yellowbroadbills have been seen feeding fledglingsof the Indian cuckoo (Cuculus micropterus)and are presumed to be a brood host of thiscuckoo. The one definitely identified egg ofthe local subspecies of the Indian cuckoo isa fairly close match for the broadbill egg incolor and size.
Though only casually studied. mostbroadbills are frequently seen and even theleast known, the Philippine and Africangreen, are unlikely to prove rare once theirhabitats have been explored. With the restof their communities, most nevertheless facethe threat of habitat destruction.