New research shows one of our most secretive native birds, the Australasian bittern or matuku, may be rarer than previously thought.
It also highlights the importance of New Zealand’s wetlands.
GPS tracking of matuku/bittern has, for the first time, revealed that this threatened swamp dweller flies more than 300 km between wetlands in the eastern South Island as well as large distances between North Island wetland sites.
Previously it was thought bittern ranged only small distances from their home wetlands.
The Department of Conservation-led study shows that bittern rely on a network of wetlands, to feed and breed in.
It also means matuku/bittern may be rarer than previously thought as birds have probably been double-counted in local counts in different parts of the country.
Conservation Minister Eugenie Sage says Bittern are secretive birds that use a freeze pose to hide among wetland vegetation and are expert at evading people.
“The GPS tracking has given new insights into their behavior and habitat requirements,” sash says.
In the study male bittern were tracked flying 330 km from Te Waihora/Lake Ellesmere in Canterbury to wetlands near Blenheim during the breeding season last spring.
They also flew 117km from Whangamarino wetland in north Waikato to south Kaipara and from Whangamarino to Kaituna in the Bay of Plenty.
Eugenie says wetlands are home to precious wildlife and plants including rare and threatened species like bittern, Canterbury mudfish and swamp helmet orchid.
“They also act as natures ‘kidneys’ filtering sediments and nutrients from runoff and as sponges in the landscape helping sustain rivers and streams in times of drought.
“In New Zealand, we have lost 90 per cent of our natural inland wetlands since the mid-1800s.
“In addition, 74 per cent of our remaining wetlands are less than 10 ha in size, and wetland drainage and damage is continuing.
“We need to value all of our remaining wetlands and do more to protect them.”
Matuku/bittern have declined dramatically in New Zealand with their distribution shrinking by 50 per cent since records began before 1900.
Their populations are highly fragmented. It’s estimated there are less than 1000 birds in New Zealand and a similar number in Australia, where bittern are also found.
Bittern has the highest threat status of ‘nationally critical’.