Many of the referendum forms highlighted the need for more information
on Great Barrier Island’s endemic birds. John Ogden, Associate Professor
of Ecology at Tamaki Campus (AU) illuminates the subject and invites
those of you interested in ‘hands on’ ecology to participate...
The Trust has recently received some funding to
gather base-line data on the birds of Great Barrier. While there is
detailed information for some species, such as brown teal and black
petrel, for the majority of species nothing is known about their current
population sizes, nesting success or trends over time. Moreover, much of
the available data are hidden in Department of Conservation Reports, or
obscure publications, so that getting an overview picture is difficult.
The excellent general account by Tim Lovegrove in "Great Barrier Island"
(Armitage 2001) does not discuss numerical aspects. Recent events, such
as the influx of bellbirds following rat eradication on Little Barrier,
and the recent introduction of robins to two locations on the island,
have highlighted the need to better integrate the information available
and to set up a system for monitoring change.
Before outlining the Trust’s proposals, I’ll provide
some background. The total species checklist for Great Barrier stands at
111 species. This includes some species no longer found here, and some
marine species only occurring on land as ‘beach wrecks’. Eightytwo of
these are currently present, or at leas
t are known to be occasional
visitors to the island. This can be compared with 328 species known from
the whole of the New Zealand region since 1995 - we have about a quarter
of the total! Of the difference between the 111 which have been
recorded, and the 82 now present, 11 are known to have gone extinct on
the island since 1868, when Hutton visited the island and made a list.
The remaining 18 are very rare visitors or of uncertain status. If the
birds are divided according to main habitats we get the results in the
table opposite.
Since Hutton’s list was made in 1868 the island has
lost eleven bird species, predominantly from forest habitats. Stitchbird,
saddleback, kokako and others can now be seen on the restored Tiritiri
Matangi Island, but not on Great Barrier. Over the same time period the
island has gained 25 introduced species. These are predominantly
generalist European birds, such as sparrows and starlings, associated
with people and inhabiting open areas. Clearly the shift in the
landscape, from the forest of Hutton’s day, to the more open farmed
landscape this century has resulted in massive changes in bird
populations. In percentage terms we have lost 33% of our forest bird
species, and many of those remaining, such as pigeon and kakariki, are
in much smaller numbers than formerly. Meanwhile we have gained 74% of
our farmland birds, flooding into the new man-made habitats.
In contrast, marine and coastal environments appear
to have suffered little change. This however may not be quite as it
seems, because we have almost no data on some species. Mostly they’re
only identified for sure when they’re washed up dead on a beach. As with
many off-shore islands it is likely that Great Barrier once had huge
nesting colonies of marine birds. Although many of these may have been
exterminated before European contact, their loss may still be having its
influence on other aspects of the ecology of the island through the loss
of many tons of nitrates and phosphates formerly deposited as guano
annually into the soil of the island. With the elimination of rats and
cats from Little Barrier I anticipate that we’ll start to get more
nocturnal visits from Cook’s petrels and other sea birds looking for
nesting sites. However, unless we also eliminate cats, all we’ll see of
them will be their disembodied wings on our bush tracks.
We have lost one coastal bird—the shore plover. The
New Zealand Dotterel seems to be holding it’s population steady at c.
40-50 birds, but is still at risk from increased visitors, and their
dogs, on the nesting beaches over Christmas. We have an interesting
suite of waders visiting the Okiwi spit during migration: bar-tailed
godwits and Pacific golden plover, and occasionally rarities such as
whimbrel and large sand dotterel. Some of these species migrate to and
from Siberia each year. In addition we have South Island visitors such
as wrybills, banded dotterel and pied oystercatcher. Even our resident
dotterels and variable oystercatchers seem to mostly go to Whangapoua
for their winter holidays.
We are fortunate in still having one large wetland,
Kaitoke Swamp, but unfortunately it, like the others, is inhabited by
rats, cats and pigs. Despite that, it is the key site for fern-birds in
the Auckland region. Other wetlands, such as those formerly behind the
dunes at Awana, Claris and Medlands, have been drained and their native
birds have been replaced by the introduced generalists. We still have
banded rail; spotless crake is probably, and marsh crake possibly, still
present. Bitterns turn up occasionally, but seem to be nesting no
longer. Brown teal are hanging on due to intensive management at Okiwi,
but grey duck may have been totally replaced by mallard.
The Great Barrier Island Charitable Trust proposed a monitoring plan, and has
received funding for it from the Dept. of Conservation (Advice Fund) to
produce an annotated checklist. We’ll carry out counts of selected
species over one weekend every three months. This will require a team of
observers, scattered at key locations across the island and co-ordinating
their counts. If you’d like to be involved or want to get more
information contact John Ogden (09 4290 980) Email: j.ogden@auckland.ac.nz)
or the Trust secretary Fenella Christian (Fenella@xtra.co.nz).
You don’t need to be a whiz ornithologist to do this. If you have a pair
of binoculars it will certainly help, but counting sparrows, kingfisher
nest holes in roadside banks or moreporks calling at night, is not
rocket science. The main requisite is enthusiasm!
