Hutton’s list in 1868, the birds of Great Barrier Island have changed
drastically. At least 12 species have gone extinct on the island, and we
have gained a further 25 introduced species. Some native species are
left with critically low populations, which are highly vulnerable to
predation or habitat change through drainage and the spread of exotic
weeds in wetlands. Tomtit and kakariki fall into the first category,
while bittern, spotless crake and fern-bird are in the latter. On the
shore the “Nationally Vulnerable” New Zealand dotterel has shown a slow
decline since counts began in 1998, and the current population is only
c. 50 birds – perhaps 15 nesting pairs – for the whole island. Likewise,
the nesting population of black petrels on Hirakimata has shown a steady
decline. The current population may be c. 4000 birds, but the rate of
decline averages 122 birds per year!
However, one iconic species, which seems to be hanging on is the brown
teal or pateke. Numbers certainly declined since from the mid 80s to c.
2000, but since then total counts seem to have crept up slightly (see
Figure). The results are difficult to interpret, since counts are made
at recognised flock sites (only) each year, and the numbers not present
at the flock sites cannot be assessed. However, a positive trend is
certainly better than a decline! As most of the pateke on the island are
in the Okiwi basin, where serious DOC research commenced in 2000, it
looks like the DOC have been doing something right! We should all
congratulate them on this work.
Having said that – the sad truth is that there is still a long way to go
to turn things around for the biodiversity overall.