Notes on the New Zealand Dotterel in Eastern Bay of Plenty
by Bill Sloan, OSNZ, 1924-2005.
With the exception of a few birds on the east coast in the Gisborne area and the very odd
bird on the west coast, the Bay of Plenty is as far south as the northern sub–species of the
N.Z. dotterel, aquilonius, is found. It is estimated that there are about 1,350 of this subspecies and
rather less than 100 of the southern obscurus subspecies which is found on
Stewart Island and which is a slightly larger bird. In the eastern Bay of Plenty the birds
nest on the dunes at several estuaries in the Opotiki area, namely those of the Waiotahi,
Waioeka and Waiaua rivers where they have been extensively studied over recent years by Mr A
Glaser of the Department of Conservation. They also nest at Ohiwa harbour further west and at
Whangaparaoa near Cape Runaway.
Trapping of potential predators has been carried out by
D.O.C over recent years in the Waiotahi, Waioeka and Waiaua areas — the principal predators caught being hedgehogs, stoats, and weasels. The population of black–backed gulls,
Larus dominicanus, is reduced when they become dangerous to eggs or chicks. I have
noticed that quite often three chicks are hatched but are quickly reduced to two — the parents being unable to protect the third. Over recent years the population of spur–winged plover, Vanellus miles, has greatly increased and they are often to be found in large numbers
in the dotterel nesting areas. Although there are records of these birds molesting chicks
their principal detrimental effect is interference with the chicks’ access to food.
As a result of Mr Glaser’s work it has been shown that a dotterel having lost its nest through predation or any other cause will frequently nest again, if necessary, two or three times.
Through banding it has been proven that fledglings disperse quite widely, a bird hatched and
banded at the Waiaua estuary was seen at Pollen Island in the Waitemata Harbour area.
After nesting the local dotterels flock at Ohiwa Harbour, starting to assemble usually in late February. In recent years this flock, at its height, has amounted to around 70 birds. It
usually starts to disperse in May. For some reason they seem to populate the furthest of the
three estuaries, Waiaua first. The birds are very territorial and much squabbling takes place
when a bird encroaches on someone else’s patch.
It is suspected this year that there
may be a female/female pairing at the Waiotahi Estuary. It is know that there are only two
pairs at this location but there are three nests containing eggs.It is possible that one nest
has been abandoned and the pair re nested but this is not thought to be the case. Advantage
has been taken of female/female pairings in places where the birds are particularly scarce by
robbing nests which will be replaced by fertile hens and giving the eggs to the unmated bird
to incubate.
Six years ago a stoat den with kits was found at Waiaua and on analysis
the remains of 11 dotterels were identified; since the stoat probably hunted over night and
the male bird is known to incubate at night a disproportionate number of pairs would have been
broken. However it seems that there must be a “pool” of birds somewhere possibly local
fledglings because in the season following the number of birds breeding at Waiaua was back to
the usual 6 or 7 pairs.
One advantage that the dotterel nesting areas in this region
have over many of those further north is that they are not plagued by holiday makers to any
great extent; in some places unless chicks are fledged by Christmas little hope is held out
for their survival as a result of human interference.
