by John Ogden
Photo of bittern chick taken on the
hot-springs track on
16th January 2013. Thanks to Herman and the Allom family.
2012 data: Amelia Geary and
Steve Corin have produced a draft report on the bittern monitoring
organized by Amelia and carried out by a few Brave Barrier Souls over
three mosquito-ridden nights last September (2012), and again for a
night in November. The results were initially disappointing as not much
was recorded by the 24 participants during the total of 95 hours of
listening for bittern “booms”. However, the summarized data suggest that
at least six bitterns were recorded, and that there is a small breeding
population still present on the Island. Amelia also collated and graphed
the bittern sightings made since 2008 on Okiwi Station.
2000 – 2012 additional data:
In September 2006 the GBICT organised a ‘bittern
listening’ (17 participants) at dawn and dusk at four locations around
Kaitoke swamp and at two locations in the Okiwi/Whangapoua swamp area
2006). Also, there are casual observations by various people, which I
have collated since 2000. Although most of these additional data
are from areas around the Kaitoke swamp (Kaitoke Swamp, Kaitoke Bridge
area , Oxborough’s property, Golf Club and Claris Club, Police Station
Swamp), other areas include swamps at Medlands , Sugarloaf Creek,
Kiwiriki Creek, Coffins Creek, and the Kaiarara. At the northern end of
the Whangapoua estuary bitterns have been seen on the Waikaro block.
Clearly, although sightings are few, bitterns are at least occasionally
present on swamps throughout Great Barrier Island.
Bittern sightings or booming
in the Kaitoke Swamp and environs 2000-2013.
Dark bars represent the start of summer
periods in which nesting definitely occurred (young seen). Black
outlines represent years in which booming was recorded.
On average only one or two observations
have been recorded each year in the Kaitoke area (Fig.1). However it is
noteworthy that two definite observations of fledged chicks have been
made (2003, 2012) and two other observations of (probably) two birds
close together (2006, 2012). Booming indicates that nesting has probably
occurred in at least six years.
Booming and nesting occurs in the Kaitoke
area from September to January, while on the Okiwi Station most
observations are between March and July (Fig 2). These observations are
suggestive of nesting in the Kaitoke area and subsequent dispersal
juveniles?) to the Okiwi Block. Probable bittern booming has also been
heard in the valleys draining into Port Fitzroy Harbour (Kaiaraara, Coffins
Creek and Kiwiriki) the September – November period.
Summary of bittern
observations on Great Barrier Island.
Red bars are DOC data from Okiwi
Station May 2008 – April 2013 (n=28). Green bars are from locations on
or close to Kaitoke Swamp 2000 – 2013 collated by J. Ogden (n= 16).
Running mean is the smoothed total of these two locations plus
observations elsewhere on GBI (total n=59). Dark green bar (Jan.)
represents fledged young.; green with black outlines, all booming
Comparison with earlier data:
Bittern was recorded in the first account of the birds of Great
Barrier (Hutton, 1868)The number of bitterns found in subsequent studies
is similar to that recorded here; Bell and Braithwaite (1964) indicate
at least eight birds in 1960, seen or heard at Whangapoua Swamp,
Sugarloaf Creek and Kaitoke, while Ogle (1981) records birds at five
locations (Kaitoke Swamp, Whangapoua Estuary margin, near Motairehe,
swampy pastures central Oruawharo Bay, and near Okiwi airstrip). Bell
and Braithwaite visited Great Barrier in June and December, while Ogle’s
observations were made in March and April, so the latter’s observations
were made outside the usual booming season. Ogle (1981) thought that it
was possible that bittern distribution on Great Barrier was being
reduced due to habitat modification. Bitterns were formerly more ‘very
numerous’ in the swamp behind Whangapoua Bay according to the Mabeys
(quoted by Bell & Braithwaite, 1964) and were also frequently seen at
Awana before the swamp was drained (Muriel Curreen; personal
communication c. 1998). Overall, these earlier reports suggest that
bittern were more widespread and abundant than is the case now.
To all those people who gave up their evenings or mornings to sit about
listening for bitters – a big thankyou! Too many to name individually
but you know who you are. Many thanks also to others who phoned or
Emailed their observations.
The community has many eyes and ears and if data are recorded and
collated it is surprising what can be discovered.
Bell, B. D., & Braithwaite D. H. 1964. The
birds of Great Barrier and Arid Islands. Notornis 10:
Geary, A. & Corin S. 2013. Monitoring
Report. Australasian Bittern. Great Barrier Island. 2012. Dept of
Hutton, F. W. 1868. Notes on the birds of
Great Barrier Island. Transactions and Proceedings of the New Zealand
Institute 1: 104-106.
Ogden, J. 2006. The
Second Gt. Barrier Bird Count. Environmental News #8 (Spring 2006), See
also: GBICT; Biodiversity Advice Fund Report 2. (Ref No. AV207).
Ogle, C. C. 1981. Great Barrier Island
Wildlife Survey. Tane 27: 177-200.