Conserving New Zealand’s bitterns- an eleventh hour conservation attempt
05 September 2010
Bitterns are an icon of our wetlands. Few birds show such a high level of adaptation to wetlands than bitterns. In fact their plumage has evolved to allow then to merge in with reed beds, a habitat that bitterns are dependent upon for their survival. Sadly it is the bittern’s specialised habitat requirements that are now putting this species at risk in many regions in New Zealand. Only Northland and Waikato have significant bittern populations remaining. Throughout the remainder of New Zealand bitterns occur only in small and fragmented populations. In some regions such as Marlborough the birds are on the edge of regional extinction. In Canterbury, where I live the population is estimated at between 30-50 birds. The NZ population may be as low as 500 birds- perhaps a maximum of 2000. Still making the bittern rarer than the kokako!
With fragmentation many other factors now come into play with bittern conservation. For example with birds living in wetlands with more edge zones the chance of predation increases, sadly there is little data to confirm this, but the increase on the harrier population is likely to impact on bitterns as are mammalian predators such as stoats and Norwegian rats. Also bitterns are highly vulnerable to collision events such as getting hit but cars and flying into power lines. For bittern the bird’s decline may be one of death by a thousand cuts. Bitterns requite large, productive wetlands- a habitat still in decline. Sadly only about 5% of our original wetlands exist, and the few surviving wetlands are under increasing threat.
For me the experience of going to a wetland and knowing that no bitterns are left would make me feel empty. Bitterns really are that one bird that symbolises a sense of wilderness with wetlands. The reality is that bitterns are the test of our commitment to conserve biodiversity. As a species they have been left to the eleventh hour to consider in active conservation plans. Yet there is hope. We have detailed information on the habitat requirements of bitterns and with some financial backing and commitment to create suitable habitat near where the surviving populations remain this species can be saved. Its future truly does rest in our hands!