Rigor Vitae: Life Unyielding

Monday, August 28, 2006

KINGFISHERS IN PARADISE

If you live between the 50th parallels, chances are pretty good that you're familiar with one or more species of kingfisher—quite likely you've seen a charming and colorful bird with tiny legs and a large head and bill, chipping or rattling merrily from a branch overhanging a river, or hovering in midair before plunging headlong into a pond. As uniform as most kingfishers appear, they comprise a group of three families whose affinities aren't exactly clear. Although the paltry fossil record is of little help, it can be inferred from the current biogeography that kingfishers originated in Southeast Asia, and dispersed globally from there (the African Pied Kingfisher [Ceryle rudis] and Giant Kingfisher [Megaceryle maxima] and the Asian Crested Kingfisher [M. lugubris] derived from later incursions back from the Americas). It is here, and particularly in the Indo-Australian region, that kingfishers have achieved some degree of diversity. Three Asian species of the genus Halcyon are known as Stork-billed Kingfishers. The heads and bills of these cartoonish-looking crab-specialists nearly equal their bodies in length. The four species of Kookaburra (Dacelo spp.) from Australia and New Guinea, and the related Banded Kingfisher (Lacedo pulchella) of Southeast Asia are famous for their terrestrial habits, capturing large invertebrates and reptiles on the ground. Most bizarre of all are the New Guinean Hook-billed Kingfisher (Melidora macrorrhina) and Shovel-billed Kingfisher (Clytoceyx rex), which forage on the ground, searching for earthworms by shoveling through the mud with their massive bills.

New Guinea is also home to the paradise kingfishers of the genus Tanysiptera, a complex of stunningly beautiful birds that is traditionally divided into six species, though further splitting may well be justified. At least 24 different taxa have been identified within the rather uniform genus. All of them are starling-sized birds with red bills and blue plumage in the adult, and a pair of long, streaming central tail feathers. The natural histories of all of these birds are not well studied, but so far, they don't appear to diverge much in their habits, either. Birds of dense lowland forests, they hunt mostly from a perch of moderate height, flying down to capture invertebrate prey on the ground or in understory vegetation. Paradise Kingfishers lay 2-5 eggs in a cavity excavated in a termite mound, usually an arboreal one (there is a record from New Britain in the Bismarck Archipelago of a nest in a tree cavity). Both sexes fly at the termitarium, striking it with their bills. Once the outer wall is broken away, the rest of the digging is done while perched. Both parents incubate and feed the young until they fledge, soon after which they disperse. Once a territory is established, most paradise kingfishers stay within a range of less than one hectare for the rest of their life, although the nominate subspecies of Buff-breasted Paradise Kingfisher (T. s. sylvia) migrates each year to Australia's Cape York Peninsula to breed.
Such complexes of similar but distinct animals can provide a lot of clues to how evolution and early speciation works. They are common among small terrestrial tetrapods like rodents, shrews and frogs, but much rarer among birds; the paradise kingfishers comprise one of the largest. Of the 24 or more species and subspecies of Tanysiptera, 13 are isolated on single small islands: Biak, Manam, Rossel, Boano, Buru, Bacan, Doi, Kayoa, Morotai, Rau, Kofiau, Numfor, Umboi. The evolution of these castaways is no mystery, but the ranges of some mainland taxa overlap in several places. In the southern lowlands of PNG's Western Province, and in the region east of Port Moresby, three different species occur together, exploiting similar if not identical niches, without interbreeding. The fact that paradise kingfishers move so little has probably assisted them in their radiation, along with the fact that they feed on an abundant resource. They are usually common where they occur, and competition for food does not appear to be a major limit for them, although I would not be surprised if further study found subtle differences in the niches these interesting birds exploit.

The I.U.C.N. lists four species of paradise kingfisher as species of concern, due to habitat destruction: Numfor Paradise Kingfisher (T. carolinae), Kofiau Paradise Kingfisher (T. [galatea] ellioti), Aru Paradise Kingfisher (T. hydrocharis), and Biak Paradise Kingfisher (T. [galatea] riedelii).
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upper: BUFF-BREASTED PARADISE KINGFISHER (2005) acrylic 10" x 8"
lower: NUMFOR PARADISE KINGFISHER (1999) acrylic 10" x 8"

2 Comments:

Blogger Patrick Belardo said...

Gorgeous artwork! I hope I get out there one of these days.

5:20 AM  
Blogger cpbvk said...

Thanks, Patrick. I'm betting you will.

10:45 PM  

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