The Hauraki Gulf is a seabird mecca. I don’t know how many times I have
been out sailing and come across a ‘boil up’. It’s like kids at a lolly
scramble. The water is seething with fish frantically trying to weave
themselves into a tighter and tighter ball against a massive aerial
assault and occasionally large mouths from below in the form of Brydes
whales and common and bottlenose dolphins.
The aerial assault is a combination of a ballet and a rugby scrum. The
sleek bullet shaped bodies of gannets with their wings tightly folded
against their bodies’ streak in from great heights, a flash of yellow as
the sun hits their heads and a splash as they hit the water and then pop
up with a shining silver victim. The gulls are probably the scrum
contenders as they are constantly scrapping and nicking in to steal
fish. Petrels and terns are more delicate in their meal gathering
Seabirds are birds that have adapted to life in the marine environment.
In general, seabirds live longer, breed later and have fewer young than
other birds do, but they invest a great deal of time in their young.
Most species nest in colonies, which can vary in size from a few dozen
birds to millions. Many species are famous for undertaking long annual
migrations, crossing the equator or circumnavigating the Earth in some
cases. They feed both at the ocean’s surface and below it, and even feed
on each other. Seabirds can be highly pelagic (living on the open
ocean), coastal, or in some cases spend a part of the year away from the
Shorebirds are often interchanged with seabirds. Shorebirds however
prefer to do their thing close to land. It’s the difference between
having webbed landing and paddling pads as opposed to longer, slimmer
waders. Shorebirds occupy wetlands and inshore coastal environments such
as beaches, rock pools and estuaries. The majority of species eat small
invertebrates picked out of mud or exposed soil. Different lengths of
bills enable different species to feed in the same habitat, particularly
on the coast, without direct competition for food. Many waders have
sensitive nerve endings at the end of their bills which enable them to
detect prey items hidden in mud or soft soil. Some larger species,
particularly those adapted to drier habitats will take larger prey
including insects and small reptiles. Some of our better known
shorebirds are the NZ dotterel and the variable oystercatcher but they
also include that wonderful sentinel, the grey heron which you often see
standing statue like with its lemon yellow legs in the water and then
all of a sudden it impales a struggling silver victim on the end of its
Some species like shags (alias cormorants), are in between the two.
Although they are classified as seabirds, they spend a lot of time
inshore in large, noisy colonies often in cliff edge pohutukawa on which
they snow down droppings. Their nests are nothing to be proud of –
resembling little more than a ramshackle collection of twigs, flotsam
and jetsam precariously piled together on a branch.
The Hauraki Gulf has some very special seabirds. Petrels comprise the
largest number of species feeding in the waters of the gulf and breeding
on the islands. They range from the delicate storm petrels or Mother
Carey’s chickens, to the great albatrosses and the more common
shearwaters, prions and mollymawks. At least a dozen of these species
breed on the islands. Breeding colonies are often large. This not only
makes for a very noisy neighbourhood but a very crowded one. On islands
where the ground is soft the birds make tunnel like burrows turning the
surface of many small islands into giant spongy honeycombs. If you have
ever wondered why there are not many trees on islands like the Grey
group out from Port Fitzroy, this is partly because of the poor soil but
also because of the way seabirds and their burrows have undermined the
ground and made it unstable for many large trees to anchor their roots.
The islands of the Hauraki Gulf are petrel strongholds. Cooks and Black
petrels only breed on Little Barrier and Great Barrier. Two and a half
million Buller’s shearwaters nest at the Poor Knights, the grey faced
petrel breeds on most islands (you may know these birds if you have
stayed a night on Tiritiri Island) and the sooty shearwater has small
colonies on the Aldermen, Hen and Chicken, Poor Knights and Mercury
A number of petrel species spend time in the Kaipara Harbour as well as
the Hauraki Gulf. Some enjoy endless summers, migrating overseas during
our winter months. Flesh footed, Buller’s and sooty shearwaters fly
regularly to the North Pacific and have been recorded off the
Californian coast with the Buller’s traveling as far as South America –
wouldn’t it be nice to have free air miles and a zero carbon footprint!
Many of you will have heard the distinctive calls of petrels. Groaning
or yelling sounds with some cat like (yup cat like!) mews are made by
the larger species of petrel and the shearwaters. Rapidly repeated
ti-ti-ti or kek-kek-kek notes are given by Cooks and Pycroft’s petrels.
Hence the Maori name Titi. The diving petrel makes wailing and cooing
calls but perhaps the most distinctive caller is the fluttering
shearwater which has a rapid, repetitive cry best described as a wild
The best time to hear the birds is in summer during the breeding season.
Returning birds begin to assemble offshore at dusk and as darkness falls
they move to land and descend to greet their waiting mates in the
burrows. The noise is usually greatest on dark or misty nights when the
birds need to call to make contact with their mates. I have this theory
(thoroughly untested of course!) that they also use their calls to echo
locate as they fly up valleys on their way to places like Hirakamata –
Mt Hobson. Their landing tactics are not pretty as they often crash down
through the foliage. One of the most remarkable facts is that some
petrels are occasional breeders and have extended overseas tours at
least a few years and then they return to nest within a few metres of
where they were born.
There is still much to learn about seabirds even in the Hauraki Gulf
where it seems sometimes that every man and his dog are out fishing. The
NZ storm petrel was presumed extinct for 150 years until 2003 when a
sighting was made by a group of ornithologists off the Whitianga coast.
Seabirds are affected by human use of the oceans. Marine debris is
attractive to many species as nesting material. I have seen gannet nests
off the coast of Muriwai Beach on Auckland’s west coast that were
comprised entirely of plastic and strapping from bait boxes. I have also
removed many 6 pack can holders from around bird’s necks and at
Tawharanui seen the terrible sight of a dead shag suspended in a tree
with fishing line around its neck – a terrible way to die. Picking up
rubbish particularly plastic and fishing line around our coast is such a
simple thing to do and it does make a difference. Disposing of rubbish
responsibly when boating or fishing is a simple way to help.
However the biggest threats to seabirds that nest in the Hauraki Gulf
are introduced pests namely cats and rats. Kiore predation of Cook’s
petrel chicks resulted in a 90% failure rate of Cook’s petrel on Little
Barrier Island between 1996-2003. Following their eradication from
Codfish Island Cook’s petrel achieved 80% breeding success in a 4 year
period – the same trend is being repeated at Little Barrier now that
kiore have been eradicated.
The Department of Conservation has pioneered techniques to eradicate
rodents from islands with 100% success rates in most cases. It is
important to the survival of seabird ecosystems that D.o.C is supported in
these endeavours. Seabird colonies and the rich guano in turn support
many unique species of native plants found nowhere else. Our only
dinosaur the tuatara often shares lodgings with nesting petrels as do
many species of lizards and large invertebrates.
We can all help protect the seabird islands of the Gulf by treading
gently. Enjoy small islands from a distance. Resist the urge to go
ashore, some are nature reserves and many are privately owned. Don’t
take the dog ashore for a walk, check your boat for rats regularly and
think carefully before you run a shore line from your boat to a tree –
rats run these very easily. And above all take time to enjoy the many
seabirds that call the Hauraki Gulf home.