A complete failure

When the revised version of Robertson & Heather's guide to New Zealand birds was finally released last year, some people disapproved of the fact that it retained the grey partridge in the field guide section, describing it as a 'Rare European Introduction', and including a range map which indicated that it could be found in the southern South Island.

And they had reason to, due to the fact that it has now been a great many years since a single one of them has graced New Zealand's countryside.

The introduction of the grey partridge in New Zealand, and its failure, is an interesting and unusual event in the history of New Zealand's avifauna that tends to go overlooked.

Included in the 2010 Checklist of the Birds of New Zealand is an account of its history; it was introduced in several places throughout the country in the late 19th and early 20th centuries, and 'Some of these early introductions were briefly successful but all ultimately failed'. The text goes on to say that, beginning in 1961, there were a number of serious attempts to establish the species in the southern half of the South Island, and, 'Between 1964 and 1970, 11,000 grey partridges were released in North Canterbury alone'.

The handbook section of Robertson & Heather's revised guide reads, '... a few birds persisted in Southland until at least the 1980s'. Even this, however, is a baseless statement; in the 1969-1976 survey of the distribution of birds in New Zealand, there were only three grey partridge records; one in the North Island, and two in the South, with the last of these occurring in 1975. The North Island record during this time is unusual, given that there were no releases of the species there during or shortly before the survey was underway; my guess is that it was either a misidentified juvenile pheasant, an escapee from private hands, or the remnant of an unauthorised attempt at establishing the species in the North Island.

This brings the question of, what caused this species to die out so quickly?

I think that climate can be ruled out as being the primary cause for their failure at establishing. The climate of where they were released in the South Island would not have been much different from the climate of many of the places where they are found in their native range. I believe that, in most cases, it is unlikely for any large number of birds to quickly die out with an unsuitable climate as the primary cause; after all, the myna, a species that is intolerant to cold climates which has shown that it cannot breed south of Whanganui (or Foxton?), persisted in the South Island for at least a decade when it was introduced there in the 1870s.

Predation is an obvious possibility as to why they failed to establish as well. In regards to the predators that it would/could have encountered when it was introduced to New Zealand; cats, dogs, mustelids, falcons, and harriers would have been able to take the species at any stage of life; herons, rats, pukeko, and possibly little owls would have been able to take the eggs and chicks of the species, and mice and hedgehogs would have been able to take the eggs of the species. Weka would have been a threat to the species at all stages of life as well, but from what I can tell, the range of the weka and grey partridge when the more recent attempts at establishment were made would have overlapped either only slightly or not at all. Regardless, that is a considerable number of threats to the species, and yet, wouldn't such animals as foxes and martens, among others, be predators that the grey partridge would have been adapted to avoid in its native land, meaning that the predators in New Zealand wouldn't have been unusual to it? As well as this, the California quail was fairly widespread in parts of where the grey partridge would have been introduced to, meaning that they were able to survive such pressure from predation, despite having similar habits to the grey partridge, so surely the pressure from predation wouldn't have been so extreme as to be the main reason for why the species couldn't establish there?

Finally, what I think may be the most likely reason for their failure at establishing is changes in agricultural practices. In recent years, the grey partridge has sharply declined in parts of its native range due to agricultural practices changing where they live. It's fair to assume that such practices would have effected NZ's grey partridges as well, but I have no information about this at hand.

That's it, really. The grey partridge will probably never be seen in the wild here again, given that the importation of almost all birds into New Zealand is now illegal, and that there are apparently no grey partridges in captivity here. The grey partridge should be remembered as a member of the past of NZ's avifauna, but not its present.