The sugarbirds are a small genus, Promerops, and family, Promeropidae, of passerine birds, restricted to southern Africa. In general appearance and habits, they resemble large, long-tailed sunbirds or some of the Australian honeyeaters, but are not closely related to the former and are even more distantly related to the latter. They have brownish plumage, the long downcurved bill typical of passerine nectar feeders, and long tail feathers.
Taxonomy and systematics
The genus Promerops was introduced by the French zoologist Mathurin Jacques Brisson in 1760 with the Cape sugarbird (Promerops cafer) as the type species. The name of the genus combines the Ancient Greek προ pro "close to" or "similar" and the genus Merops that contains the bee-eaters.
The relationships of the sugarbirds have been a source of considerable debate. They were first treated as a far-flung member of the honeyeater family, which is otherwise restricted to the Australasian region. Using egg white proteins in the 1970s, Sibley and Ahlquist mistakenly placed them with the starlings (the samples used were actually those of sunbirds). They have also been linked to the thrushes (Turdidae) and the sunbirds. Molecular studies find support for few close relatives, and they are treated as a monotypic family at present,
Genetic diversity
Both species have been shown to exhibit exceptionally high genetic diversity at both microsatellite and mitochondrial loci, with no signs of inbreeding and large effective population sizes.
Species
The genus contains two species:
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! Image !! Scientific name !! Common name !! Distribution
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|120px || Promerops gurneyi || Gurney's sugarbird|| Lesotho, Mozambique, South Africa, Swaziland, and Zimbabwe
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|120px || Promerops cafer || Cape sugarbird || Western Cape and Eastern Cape provinces of South Africa.
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Description
thumb|Female cape sugarbird, note the protruding tongue
The two sugarbird species are medium-sized passerines that weigh between and are in length. Between of that length is in their massively elongated tails, the tails of the Cape sugarbird being overall longer than those of Gurney's sugarbird. In both species, the tail of the male is longer than the female, although the difference is more pronounced in the Cape sugarbird. In overall body size, the males are slightly larger and heavier than the females. Both species have long and slender bills that are slightly curved, and again the females have a slightly shorter bill, leading to differences in feeding niches. The skull and tongue morphologies of the sugarbirds are very similar to that of the honeyeaters, the result of convergent evolution. The tongue is long and protrusible, and is tubular and frilled at the end. Studies of their diets found that bees in the family Apidae and flies formed a large part of the diet and that the insects were obtained by hawking.
The breeding behaviour and nesting habits of the two species of sugarbird are very similar. Sugarbirds are monogamous, and male sugarbirds defend territories during the breeding season. Females lay two eggs in a nest in a fork of a tree.
References
External links
- Sugarbird videos on the Internet Bird Collection