Saturday, 19 December 2015

Phillip Island

Phillip Island lies on the horizon, with Nepean Island in the middle distance - viewed from Norfolk Island

Phillip Island lies in the wide waters of the South Pacific ocean, about 6 km south of Norfolk Island. It is only 190 ha in area, being 2 km wide at most and 280 m at its highest point. It is only accessible by boat via a few landing places, the best of which is at the back of a small sheltered rocky bay. So, the island is rather remote and difficult to access, but well worth the effort.

The main landing site - the boat must be guided into the rocky bay, passengers jump ashore onto the wet slabs,
 then climb up the cliffs. The latter is aided by a rope and wooden steps in places.

For various reasons; difficulty of access, water supply, ruggedness and remoteness, the island has never been permanently settled by man and is in contrast a haven for oceanic birds. However, many of the original breeding birds were drastically affected by the introduction of pigs, goats and rabbits at the turn of the eighteenth and nineteenth centuries. The pigs would have eaten whatever birds and their eggs they could access, including digging up petrels from their burrows. Pigs would also have eaten much of the vegetation while the goats would have accessed even remote rocky ledges for food. Eventually these two species died out, probably via starvation or lack of water. But the rabbits persisted until they were finally exterminated in 1988. By then, the island was virtually stripped of vegetation and even now, in 2015 there are still large patches of ground denuded and badly eroded into gullies by water and wind. It will take many more years for the whole island to become vegetated again. But it will, for the whole Norfolk Island archipelago is volcanic in origin and would have been devoid of vegetation at first. It will simply take time.

Soil erosion from around the roots of this ancient Phillip Island hibiscus tree Hibiscus insularis have left it very exposed
but it clings on to life

Although most of the top soil has gone from the island, petrels still manage to nest in natural rocky hollows or dig shallow burrows where they can, such as in the soft weathered basalt. Species breeding there now are Providence Petrel Pterodroma solandri, Kermedec P. neglecta, Black-winged Petrel and White-necked petrel P. cervicalis, along with Wedge-tailed Shearwater Puffinus pacificus and Little Shearwater P. assimilis. The island must have been covered by these birds nesting-burrows in the past, and just how many birds bred there?

It is perhaps good timing that the island is now rabbit free, as these birds either no longer breed on Norfolk Island or many that try are eaten by rats and cats. In thirty years, Phillip Island has changed from an ecological disaster area to a potential wildlife refuge. Several species have been driven to extinction on Norfolk Island, largely because of rats and cats, and others such as the Green Parrot might in future find sanctuary on Phillip Island. Although they would probably need to be introduced to do so.

The vegetation is becoming re-established, mainly in the beds of gullies and spreading out from there.
But there are still large areas with no topsoil and badly eroded bedrock

For the present, petrels seem to fill the air at times as they whiz past, and their presence gives an optimistic outlook for the island. The eradication of rabbits from the island has been a great success story.

Black-winged Petrels Pterodroma nigripennis sweep low over the island and are ever-present,
although, as they nest in burrows they are seldom seen on land during daylight hours 

The other obvious bird on the island is the Tasman Masked Booby, a bird endemic to the Norfolk Island Group, Lord Howe Island and Kermedec Island. These birds breed in a few scattered colonies across the island, placing their nests on the ground in amongst the bushes or on the edge of cliffs alike.

Tasman Masked Booby  Sula dactylatra tasmani - distinguished from other Masked Boobies by their dark brown, not yellow irides. The seeds stuck to his breast and under the tail show how plants can be transported between remote islands by birds and barren islands can become vegetated

The boobies usually lay two eggs, but only one chick fledges, the second egg seeming to act as a reserve in case the first doesn't hatch. Incubation takes over six weeks and then the chick takes seventeen weeks to fledge. The birds on Phillip Island in December had eggs, small chicks and chicks ready to fledge, so the whole breeding season must be rather protracted on the island.

A family group of Tasman Masked Boobies, the adult female is on the left - she has a duller bill than the male

These boobies eat mostly fish and flying fish are a major prey, along with squid. Many of the chicks had both parents in close attention, so it seems that there are abundant supplies of these foods in the birds' fishing grounds.

The chicks take 17 weeks to fledge - this one still has a few weeks to go 

The chicks are soon too large for the adults to cover and brood efficiently, so they have adapted a thick growth of down and as they grow older they seem to dwarf their parents which have slim slick plumage.

The younger chicks are covered with white down - and seeds stick to that readily 

Other sea birds nesting on the island include Sooty Tern Sterna fuscata, Common Noddy Anous stolidus, Black Noddy A. minutus  and Grey Ternlet Procelsterna albivitta, all adding their chatter to what is an annually increasing population of seabirds. And another seabird there is the Red-tailed Tropicbird.  These birds are so flamboyant when flying with their pearly white wings and red tail streamers. But, when nesting, they tuck themselves quietly into niches on the cliff tops. They stand, or rather sit, their ground tightly when approached. As we walk by, they simply give a straight-in-the-eye stare.

A Red-tailed Tropicbird Phaethon rubricauda sits on its nest
typically set in a small enclave at the top of a sea cliff behind some vegetation

Although, I'm sure they could give quite a sharp peck with those bills.

A Red-tailed Tropicbird's face

This is not a comprehensive account of Phillip Island, simply a flavour of my experience from one day there. And this is a record of only some of what I saw, there is so much more. I was there as part of a team organised by Neil Hermes on behalf of the Canberra Ornithologists's Club and The Norfolk Island National Park who set up a baseline survey of the birds on the island. For more information on the island follow this link and to organise a trip there follow this link.

And all the while the petrels continue to wheel around the island

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