Great Barrier Island
PATEKE / BROWN TEAL RECOVERY PROGRAMME
Great Barrier Island (Aotea) is the main stronghold for pateke and this is largely because many of the introduced predators that roam the mainland are not on the island.
The 2004 island-wide count showed there was a minimum of 600 pateke, but as the count does not cover every suitable habitat, it is estimated there are more. A lack of stoats, ferrets, weasels, hedgehogs and Norway rats is a major factor in the survival of brown teal on Great Barrier. These introduced mammals are particularly tough on ground-nesting birds around New Zealand. Great Barrier is also possum-free. The ducks still have to contend with cats (feral and pets), dogs, ship rats, kiore (Polynesian rat), Australasian harrier, pukeko, vehicles and other threats.
Other species to benefit from fewer predators on Great Barrier are banded rails, New Zealand dotterel, black petrel, kaka and a variety of lizards.
The preferred habitat for pateke on Great Barrier appears to be where fresh water meets salt water. Most bays that have a reasonable amount of freshwater running into them have at least one resident pair of pateke. The ducks spend a lot of time dabbling on the stream edges and pebbled bays feeding on invertebrates and small shellfish. The major water systems, wetlands and estuaries on the east coast of the island can carry up to 100 pateke or more when feeding conditions are right. Large flocks can be seen dabbling in the tidal sand and mud over summer.
Grazed pasture is another prime feeding habitat for pateke and the coastal farms at Whangapoua, Harataonga, Awana, Kaitoke and Medlands carry much of the island’s pateke population. This fertile farming environment of short cropped grass and cow-pats has plenty of invertebrates and clover that the ducks feed on.
However, pateke are also seen deep in the bush. Hunters come across them in streams and seeps in the interior of the island and radio-transmittered ducks have been tracked deep into the bush. When the pastures of the east coast dry out in the summer months and invertebrates are less plentiful, the ducks tend to head for flock sites, which are situated around creeks, drains, estuaries or wetlands, or try their luck foraging in the bush.
Recent flock counts suggest that weather and the abundance of food influences the success of breeding. More juvenile pateke make it through to adulthood and the population grows during wet summer seasons when there are plenty of invertebrates in the moist pasture. In dry years when there is less food, fewer juvenile ducks survive and the population grows little or at all.
Interest from locals
Most Great Barrier Islanders are acutely aware of how rare pateke are and how important the island is to their survival. Many locals have pateke on their property and actively look after their ducks. Some landowners have created or enhanced ponds and wetlands. One of the larger flock sites (Blackwell’s) is a pond that has been enhanced by the landowner. Some landowners have fenced and enhanced pateke nesting habitat on their properties, while others trap rats and cats. Many locals train their dogs not to be interested in ducks and some of the largest flock sites are within a few hundred metres of farm kennels. Locals help out with the annual flock counts and phone in regularly with bits of information about the ducks on their properties. Interest from locals is vital to the survival of pateke on Great Barrier.
Outside of the breeding season (June to November) many pateke congregate at traditional flock sites around the island. As a rule these sites are on a reliable water source, are close to feeding grounds and have a source of cover from avian predators. Often the source of cover is a large pohutukawa tree overhanging the water and the ducks roost under it or in its branches during the day. Other cover might be manuka, kanuka, flax or gorse nearby or overhanging the water. The largest flock site on the island, Burrill’s drain, has up to 200 pateke in it at the height of the dry season. It is a deep, open drain with manuka scrub on the sides that runs through rough pasture down to Whangapoua Estuary.
Each year there are flock counts at most of the known flock sites around the island. All the sites are counted on the same day to lessen the chance of the same ducks being counted at two different sites. This job involves many staff and volunteers. Two counts are carried out, one in February and one in March, and the average is taken. A worrying trend between 1994 and 2000 showed pateke numbers had almost halved on the island.
Whangapoua (Okiwi) Basin Management Programme
In response the falling numbers of pateke, the Brown Teal Recovery Group and DOC set up a pest management project based on mainly conservation land in the Whangapoua Basin in the north of the island. The main pest threats were identified as cats and pukeko. Small scale cat-trapping and pukeko-culling started in 2000 and became a 40-hour a week job for a ranger in winter 2001.
More than 100 cat-traps are placed around the Basin and checked five days a week. Traps are baited with rabbit, fish-frames, jellymeat and other lures. More than 300 cats have been caught during this time. Juvenile pateke are most vulnerable to attack by cats when they are unable fly and later while they are still naïve and have little experience of predators. All pateke are vulnerable to cats when food is scarce, as they are often weak and have to spend much longer periods foraging.
Pukeko can be quite aggressive and displace pateke from their territory. Pukeko have also been seen robbing pateke nests and preying on eggs and chicks. The Recovery Group suggests keeping pukeko numbers down to four pukeko per 10 hectares to lessen their effect on pateke. More than 2000 pukeko have been culled in the Basin in the past four years.
During the management programme pateke numbers in the Basin have increased from 208 in Feb/Mar 2000 to 314 in Feb/Mar 2004.
Pateke Monitoring in Whangapoua Basin
Over the past decade the pateke population in Whangapoua has been monitored and the programme continues to be developed by the Recovery Group as more is learned. Monitoring is now concentrating on measuring nesting success and the amount of juvenile ducks that join the adult population.
To measure nesting success, adult females are fitted with small transmitters and are tracked during the breeding season. A ranger keeps an eye on the nests and inspects them when the female pateke moves off. From the egg shell remnants, the ranger can tell if the eggs successfully hatched, were eaten by a predator or were unfertile and abandoned. Most nests have between four and eight eggs, with six being the most common number. The monitoring is showing that most pairs don’t have trouble hatching eggs.
Raising chicks is another matter. Although there are no stoats, weasels, ferrets, Norway rats or hedgehogs, most broods of ducklings get whittled down quite quickly. In first month of the ducklings’ life they are the most vulnerable – from cats, pukeko, harriers, eels, getting run over or just getting separated from the parents in thick vegetation.
Difficulties don’t end there. Transmitters are placed on some juvenile ducks just after fledging and they are monitored through their first summer. The idea is to find out how many juveniles make it through to join the breeding population. The monitoring is showing that in dry summers, young pateke are starving to death. A dozen dead juvenile ducks were sent to Massey University for study in November and December 2003 during a very dry spring and early summer. After analysing the ducks’ wing fat (a measure of a bird’s condition) it showed that they were in extremely poor condition. Far fewer adult ducks died during this time. It is thought that juvenile ducks do not have the experience to successfully feed themselves when food is hard to find in dry summers.
In the 1990s DOC purchased the 514 hectare Okiwi Station in the Whangapoua Basin to manage as pateke habitat. Parts of the hill block have been retired and all riparian areas have been fenced and encouraged to regenerate. These measures are to enhance pateke nesting habitat. The remainder of the farm is leased to a local farming family who own the neighbouring farm. The pasture is grazed to try and create the best habitat for pateke to dabble for invertebrates and clover. A farm is not totally natural pateke habitat, but anecdotal reports show that pateke numbers in the Basin were much lower before Okiwi Station was developed in the 1960s. While pateke remain critically endangered, DOC will continue to provide the mix of pastoral and natural habitats in the Basin that the ducks thrive in.