DUNZ and Bittern Research
For the past four years Ducks Unlimited NZ has been supporting a national bittern research programme to help save the critically endangered Australasian bittern.
The focus of this project is to identify threats and reverse species declines. Ducks Unlimited has been fundamental to the project so far by providing 19 VHF transmitters, 3 GPS tags and funds to support the work of researcher Emma Williams. Ducks Unlimited transmitters have already taught us a number of things:
Large network of wetlands required
Bitterns rely on a large network of wetlands rather than individual sites to sustain themselves throughout the year. For example, Hawkes Bay bitterns are known to visit several wetlands regularly through summer, autumn and winter within a 15 km radius of their breeding site at Lake Whatuma. This information is fundamental for saving the species as it shows there is a need to manage and protect wetland networks on a landscape scale. They visited lakes, swamps, spring-fed creeks and farm ponds as part of this network.
Alternative sites needed
Bitterns can move long distances. A juvenile rehabilitated female bittern in Canterbury, that was carrying a DU transmitter, moved from the Waimakariri river mouth to the Opihi river mouth. That’s over 100 kilometres! – Again, this is important information. Results to date suggest long distance movements occur when sites become unsuitable and birds are unable to find alternative sites nearby. Wetlands are naturally dynamic environments – when conditions change at one site, bitterns need access to alternative sites close by (that are safe and suitable) so they can survive.
Poor rehabilitation survival rate
DU transmitters have been fitted to sick and injured bitterns after they have been rehabilitated in Canterbury, Waikato and Bay of Plenty. These transmitters have been able to tell us that bitterns rarely survive after rehabilitation and starvation is a key cause of their demise. This has resulted in some key changes to the way that bitterns are rehabilitated.
Care needed in wetland management
The way we manage our wetlands has a direct impact on the species survival. The body of one rehabilitated bittern carrying a DU transmitter was found buried under debris removed during drain clearances.
It is hoped that this work, a collaboration between Ducks Unlimited, Department of Conservation’s Arawai Kakariki fund and Massey University, can continue to push the boundaries of what we know about bitterns, to help prevent extinction of the species.