I’m sure everyone has seen this large bird with striking iridescent purple plumage and a prominent red shield and beak, foraging around the edges of dams, lakes and swamps. The Australasian swamphen (Porphyrio melanotus) is a species of swamphen found in the Australasian region, including Australia, New Zealand, and parts of the southwestern Pacific. There are 6 other Swamphen species in the Swamphen complex group, and they are all members of the rail family, Rallidae. They are the:
- Australasian swamphen – Australasia, South Pacific Islands
- Black-backed swamphen – Indonesia
- Western swamphen – Mediterranean Spain, France, Portugal and North Africa
- African swamphen – Africa
- Grey-headed swamphen – South-East Asia, India, Middle East
- Philippine swamphen – Philippines
The Australasian swamphen is highly opportunistic, thriving in both natural and human-modified environments. While they prefer vegetated areas around swamps, they have proven to be very adaptable, feeding in open pasture and roadside verges. Their diet is omnivorous, consisting mostly of a variety of plant materials, insects and aquatic creatures. They are accomplished swimmers and fliers, readily taking to the air when disturbed.
Australasian swamphens have an interesting social structure. They are generally found in small groups that consist of more males than females. More than one male will mate with a single female. All family members, and occasionally the young from a previous brood, share in incubation and care of the young. The nest consists of a platform of trampled reeds with the surrounding vegetation sometimes being used to form a shelter. Often two broods will be raised in a year.
The Australasian swamphen has five subspecies distributed as follows:
- m. melanopterus – northern and south-eastern Sulawesi, the Moluccas, Lesser Sundas and New Guinea region.
- m. pelewensis – Palau (western Caroline Islands, western Micronesia).
- m. melanotus – northern and eastern Australia, Tasmania, Lord Howe and Norfolk Islands, as well as the North, South, Stewart, Kermadec and Chatham Islands of New Zealand.
- m. bellus – far south-west Australia.
- m. samoensis – Admiralty Islands to New Caledonia, Solomon Islands, Fiji and Samoa.
On a recent visit to New Zealand, I visited the Tawharanui Open Sanctuary on the Tawharanui Peninsula. As an aside, this sanctuary is an interesting model in that conservation, farming and recreation are all combined with considerable success, including the introduction and breeding of Kiwis and Takahe (Porphyrio hochstetteri). The Takahe, a distant relative of the Australasian swamphen, looks like a stocky, enlarged Australasian swamphen and is the largest living member of the Rail family.
Upon entering the sanctuary through an electric gate in a predator proof fence, I was surprised to see a very large number of Australasian swamphens, grazing on open pasture, maybe one kilometre or more from the nearest water. This prompted me to investigate their origin. There are a considerable number of Australian birds deliberately introduced into New Zealand and I mistakenly assumed this was just one more of them.
The evolution of the Australasian swamphen is much more complex than I expected. It has been suggested that the ancestors of the swamphens originated in Africa many million years ago with a number of dispersions occurring into the Indo-Pacific region. Living in Australia, one often wonders about the Northern Hemisphere centric models of evolution. Nevertheless, an ancient ancestor of the Swamphens probably arrived in Australasia prior to the separation of Australia and New Zealand, thought to be around 80 million years ago. This ancestor probably evolved into the Takahe of which there are 2 species, one of which is extinct and the other being “rediscovered” in the South Island in 1948. The recovery of the South Island Takahe is a remarkable story with an estimated current population of around 500 birds in several locations. Being a flightless bird, the Takahe is very vulnerable to predation by mammals, probably the reason why there are no ancestors in Australia. We were fortunate to see 5 Takahe in our visit to the Tawharanui Open Sanctuary, possibly the entire population at that location!
Getting back to the Australasian swamphen, it has been suggested that a further dispersal of a swamphen ancestor into Australasia took place around half a million years ago, evolving into the current Australasian swamphen. Australasian swamphens then self-introduced into New Zealand from Australia 500-1000 years ago. The Pukeko, as the Australasian swamphen is called in New Zealand, is the same species as the Australian bird. They may be a little larger and were grazing on open pasture in a manner not usually seen in Australia. This may be due to the lack of predators in the Sanctuary.
The factors that have driven changes in avifauna in the past are very important when we consider our rapidly changing world and the impact these changes have on our avifauna now and into the future.
Stephen Prowse
