A rare animal that is an invader

The Kelp Gull is a large black-and-white sea-bird that feeds on marine invertebrates and vertebrates, eggs of other birds, fledglings and carrion.  It is found along the coastline in similar areas to the Pacific Gull (Larus pacificus) and seldom ventures further inland.  The Kelp Gull is not listed as rare or threatened in Victoria or Australia, it is classified as Least Concern in the IUCN Red Book.

Until the late 1950s the Kelp Gull was considered to be a resident of coastal South Africa, South America, New Zealand and some southern Pacific islands.  There are two sub-species, L. d. vetula (Cape Gull) which breeds in South Africa and is considered by some ornithologists to be a distinct species, and L.d. dominicanus (Kelp Gull or Karoro in New Zealand) which breeds in the other countries.  The dominicanus sub-species was recorded as a vagrant in Australia from 1943 (and perhaps earlier) but it was in 1958 that the first birds began breeding in this country. Since that time Kelp Gulls have increased in number along the southern and eastern coasts of Australia and records of breeding animals are known from Westernport, near Phillip Island, since the late 1960s.

There is little doubt that the Kelp Gull arrived in Australia by its own means (it was not captured and released here by humans) and as such its presence is regarded by many biologists as part of a natural process of range extension (the numbers are on the increase in New Zealand and South Africa). Nevertheless, the literature about this bird is liberally laced with comments that suggest the species is invading habitat occupied by the native Pacific Gull and may be displacing it. The fact that this displacement concerns some ornithologists and also that the Pacific Gull (classified as near threatened in Victoria) is regarded as the genuine native animal suggests that the Kelp Gull is considered to be an undesirable alien by some.  On the other hand, the Department of Sustainability and Environment (DSE), accepts the species as native to Victoria.  The Kelp Gull was initially classified as rare in Victoria and was later upgraded to critically endangered, on the basis that there is only one small breeding colony in the state.  Recently this classification has be rescinded.

In 1981 a single Cape Gannet (Morus capensis) joined a large colony of Australasian Gannets (Morus serrator) at Wedge Light in Port Phillip Bay, south of Melbourne. The animal was probably a wandering individual which came from near South Africa where the species is quite common and it was the first time this species had been recorded for Victoria. A few years later several more individuals were recorded from another Australasian Gannet colony on Lawrence rocks near Portland in south-western Victoria.  The new arrivals, which look very similar to the local birds, have settled in well enough to breed with Australasian Gannets and there are a now a few hybrid individuals in Victoria.   The Cape Gannet was initially classified as rare in Victoria, then critically endangered and now is unclassified. The species is classified as vulnerable in the IUCN Red Book

An invasion of this sort by species released by humans (e.g. Mallards which breed with local Pacific Black Ducks) is almost always regarded as something undesirable that needs to be controlled.  With species that get here by themselves there is an ambiguity that seems to have been left unresolved.  If the Kelp Gull and Cape Gannet are truly native their relatively low numbers and uncertain breeding status should classify them as threatened at some level.  If they are not native then they should be categorised as such and perhaps eradication programs need to be put in place.