<i>PROMEROPS</i> AS A THRUSH, AND ITS IMPLICATIONS FOR THE EVOLUTION OF NECTARIVORY IN BIRDS

Olson, Storrs L.; Ames, Peter L.

doi:10.1080/00306525.1984.9634490

Cited by 6 publications

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“…Ancestral hummingbirds and sunbirds were presumably small birds with narrow tongues. Narrow tongues can become more efficient at acquiring fluids simply by having flexible lateral margins that can curl upwards to produce a tube or trough with an internal diameter of less than 0,5 mm, African sugarbirds {Promerops) are relatively large nectarivores (>30 g, Collins & Paton 1989) that apparently evolved from a thrush (Muscicapidae, Olson & Ames 1984), As expected the tongues of sugarbirds resemble those of honeyeaters (Bock 1985), Furthermore sugarbirds frequently exploit various Proteaceae in southern Africa that present nectar in similar ways to Australian banksias (Collins & Rebelo 1987),…”

Section: The Influence Of Tongue Morphology On Nectar Extractionmentioning

confidence: 99%

Bills and tongues of nectar‐feeding birds: A review of morphology, function and performance, with intercontinental comparisons

Paton

Collins

1989

Australian Journal of Ecology

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The bills and tongues of nectar-feeding birds differ from continent to continent. The major differences are that: (i) the tongues of 4 tistralian honeyeaters are broader any more ftmbricated at the tip than the bifurcated tongues of sunbirds and hummingbirds; (ii) ihe bills of hummingbirds are more uniformly narrow and taper less markedly towards their tips than tiiose of sunbirds and honeyeaters: and (iii) bill curvatures are generally greater for sunbirds and honeycreepers than for hummingbirds. A variety of hummingbirds has straight or even slightly upturned bills, while bills for all sunbirds, honeycreepers and honeyeaters are decurved to some extent. Despite differences in tongue morphology, hummingbirds, sunbirds and honeyeaiers extract nectar at a similar range of rates, averaging approximately 40 fiE s~ 'from ad libitum feeders, and 1-15~' from flowers. All tongues collect nectar by capillarity, with licking rates of 6-17 s~'. Eicking behaviour has been little studied, although speeds of licking respond to changes in sugar conceniraiion and corolla length. The tongues of honeyeaters are broad, and may need to be brush-lipped in order to allow capillary collection of neeiar. Brush-tipped tongues can cover large surface areas on each lick, and may allow honeyeaters io exploit nectar and honeydew thai is thinly spread over large surfaee areas. Bill lengths of neciarivorous birds are similar in all regions, though species of hummingbird have the shortest and longest bills. Bill lengths largely determine the range of floral lengths ihal can be legitimately probed. Maximum floral lengths exceed bill lengths, since hummingbirds, sunbirds and honeveaters protrude iheir tongues beyond the tips of their bills. Rates of nectar extraction, however, decline rapidly once the floral length exceeds bill length. Decurved bills may have evolved in honeyeaters and sunbirds lo enable perching birds lo reach flowers al the ends of branches more easily. Consistent differences in bill length between the sexes suggest that males and females may exploit different floral resources or different proportions ofthe same resources. For honeyeaters and sunbirds, males have longer bills than females, bul the reverse is true for many hummingbirds.

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Section: The Influence Of Tongue Morphology On Nectar Extractionmentioning

confidence: 99%