Birds of Paradise
Birds of paradise are so named because of the bizarre appearance of most males, which have fantastic feather and plume structures and wonderful coloration, much of which is iridescent.
Most species are confined to New Guinea where the family doubtless originated, but the Paradise crow and Wallace’s standard-wing are confined to the Moluccas islands and the Paradise and Victoria’s riflebirds to eastern Australia. The Magnificent riflebird and the trumpet bird ranges also just reach Australia from New Guinea. Some New Guinea species have extensive lowland distributions but most have restricted and/or patchy ranges in the mountains at definite altitudinal zones. A few are confined to off-shore islands. Most species are wet forest birds although a few occur in sub-alpine woodlands, lowland savanna, or mangroves.
Birds of paradise are stout crow-like or starling-like, round-winged, very strong-footed birds. The plumage is extremely varied. From black with brilliant areas of metallic iridescence in some to brilliant combinations of rich yellows, reds, blues, and browns, with rich pastel areas of specialized display plumes or weird head or tail “wires” of modified feathering in others. Each genus of the polygamous species has a basic male plumage structure peculiar to it which is manipulated in certain ways during ritualized display sequences.
The five generally uniform blue-blackmanucodes (Manucodia species), and the generally black Macgregor’s bird of paradise, show no sexual differences in plumage and are monogamous, and the similarly dull-plumaged Paradise crow and the two paradigallas are presumed to be like-wise. The other more colorful and sexually dimorphic species are known or presumed to be polygamous, with males being promiscuous and females raising the young alone.
Bills of birds of paradise vary enormously, from short stout crow-like generalized hills, and finer starling-like ones, to very long fine sickle shapes specialized for probing under moss and hark for insects and larvae. While most species are predominantly fruit eaters that also take a variety of insects and animals. Leaves and buds, sicklebills, and riflebirds are highly specialized insectivores that eat only some fruit. In the latter, longer billed species, the bill of the female is larger in most species. This is noteworthy as many birds of paradise appear to suffer from limited resources in no breeding seasons when the females move lower down the mountains than the males to limit intraspecific competition.
The incredible displays of promiscuous male birds are to impress females or, in birds such as the typical or plumed birds (Paradisaea species), which congregate on breeding grounds (leks) to establish a male dominance hierarchy. The six-wired birds (Parotid species), like many promiscuous species, display as solitary males at traditional courts or perches which young males eagerly wait to occupy at the first opportunity.
Meantime, like young male bowerbirds. They must spend years. Perhaps as many as seven, in immature female-like plumage. This situation, with adult males mating promiscuously with many females, means that there are few breeding males in the population relative to females or immature males. Pressure by the latter, in addition to that from rival adult males, ensures that only the
The fittest males can maintain their place in the breeding community and only the most vigorous immature “inherit” dies-play areas or places in leks. Interestingly, captive young male birds of paradise have been noted to breed at a relatively early again in the absence of adult plumage males. Suggesting hormonal activity may be restricted by the presence of dominant adult males. No such inhibition however acts on females, which are capable of breeding at two to three years old.
While a breeding system in which females fertilize many females has brought about evolutionary rapid divergence in the appearance of the males of the various birds of paradise, they remain genetically close. Thus species markedly different in male appearance are nevertheless not genetically isolated and as a result, hybrids are a com-moon phenomenon.
Not only do species within a genus hybridize, but species of many different genera do so; in which the males of the two parent species are utterly different in appearance. In the case of male offspring from such hybridization, the characters of the two contributing species mingle to produce different-looking birds, many of which were described as new species to science before our understanding of the hybrid situation.
The fact that some birds of paradise, and bowerbirds, are monogamous and territorial, and that some of the polygamous species have displaying areas (leks) where males congregate while others display solitarily, raises the question: how did these different systems arise? It seems that the predominance of tropical forest fruits in the diet is important to the development of poly-gamy in these bird groups and that the quality of fruit and/or its dispersion in the forest in space and time may dictate the kind of breeding system and/or how males disperse and display.
Several distribution ally restricted species may be threatened by habitat destruction but, unfortunately, some species populations, such as several in Irian Jaya (Indonesian New Guinea), are still unknown and urgently require objective assessment. Perhaps the most striking of all species, the Bluebird of paradise, is presently considered to be threatened because themed-mountain forests vital to it have been reduced by encroaching agriculture. It may be further threatened by potential competition from the Regina bird of paradise. Which tolerates a wider range of habitats and abuts the lower distributional limits of the Bluebird?