The Chatham Is land Black Robin (How the world 's most endangered bird was saved from extinction)

Abstract

Editor's Note: By 1980 only five
Chatham Island Black Robins -
including just one effective breeding
pair remained. The story of the daring
bid to rescue the bird from extinction
is as d ramatic a conservation tale as
any in the world. Here, Don Merton,
the chief architect of the plan and project
leader, gives a full account and
brings readers up to date with the
Black Robins progress.
The Chatham Island Black Robin
Petroica traversi is endemic to that
land apart - the windswept cluster of
islands 850 km east of the South Island
of New Zealand known as the Chathams
group. Once widespread on the
islands, the robin, together with many 

other native birds, disappeared from
the larger islands following European
colonization early last century.
Forests and scrubland were cleared,
and rats and cats introduced. Seven
bird species were exterminated.
Miraculously however, a remnant
Black Robin population of about 20 to
30 birds persisted for the subsequent
90 years in five to seven hectares of
scrub forest on top of a 200 metre
sheer-sided rock stack - Little
Mangere Island.
Little Mangere is rarely visited, so
extremely difficult is it to climb. However,
in 1938 the late Sir Cha rles
Fleming, Al an Wuthe rspoon and
Graeme Turbott scaled the cliffs and
rediscovered the Black Robin there. 

In the 1970s, the woody vegetation
atop Little Mangere degenerated ra pidly.
The robin population plummeted
from 18 birds in 1973 to seven (two
pairs and three males) in 1976, when
the New Zealand Wildlife Service relocated
the survivors on nearby 130 ha
Mangere Island. Prior to this, 120,000
trees had been planted on Mangere to
provide additional habitat for the
robins and other native wildlife.
(How the world 's most endangered bird
was saved from extinction)
by Don Merton
New Zealand Department of Conservation
Editor's Note: By 1980 only five
Chatham Island Black Robins -
including just one effective breeding
pair remained. The story of the daring
bid to rescue the bird from extinction
is as d ramatic a conservation tale as
any in the world. Here, Don Merton,
the chief architect of the plan and project
leader, gives a full account and
brings readers up to date with the
Black Robins progress.
The Chatham Island Black Robin
Petroica traversi is endemic to that
land apart - the windswept cluster of
islands 850 km east of the South Island
of New Zealand known as the Chathams
group. Once widespread on the
islands, the robin, together with many
other native birds, disappeared from
the larger islands following European
colonization early last century.
Forests and scrubland were cleared,
and rats and cats introduced. Seven
bird species were exterminated.
Miraculously however, a remnant
Black Robin population of about 20 to
30 birds persisted for the subsequent
90 years in five to seven hectares of
scrub forest on top of a 200 metre
sheer-sided rock stack - Little
Mangere Island.
Little Mangere is rarely visited, so
extremely difficult is it to climb. However,
in 1938 the late Sir Cha rles
Fleming, Al an Wuthe rspoon and
Graeme Turbott scaled the cliffs and
rediscovered the Black Robin there.
During the final three years on Little
Mangere, only one robin chick had
survived to breeding age. Although
chick survival improved following the
transfer (five chicks in four years), the
skewed age-structure of the population
meant that recruitment of young
was offset by natu ral mortality of old
birds. Unaided, no rapid recovery was
possible and the species teetered on
the brink of extinction ; an urgent
remedy was required.
In common with some other New
Zealand endemics, Black Robins tend
to be long lived and to have a low
reproductive rate: the normal clutch
size is just two eggs and a successful
nesting cycle takes more than three
months. Thus, the species lacks the 

ability to recover quickly when its
population is reduced. However,
because Black Robins are capable of
renesting, their potential productivity
is greater. For this reason, in 1979
when the species had declined to just
five birds, I proposed cross-fostering
as a means of capitalizing upon this
potential -to boost productivity and
so quickly restore the population to a
viable level.

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