Duck hunters pioneered wetland restoration long before conservation became fashionable. Recent ecological surveys indicate that the habitat they created is helping threatened native water birds.

A repeat autonomous survey across much of the Coromandel Peninsula has shown that Critically Endangered Australasian Bittern or Matuku (the general name for herons) distribution has remained stable since the baseline survey of coastal wetlands in 2016 (Stewart, 2017). This is good news as the species has declined at former strongholds in the Waikato over the last few years. Starvation and displacement due to disturbance during their breeding season are two factors adversely affecting the species. 

This season Coromandel bittern detection rates relative to other sites in the Upper North Island also appear to be good. The coarse autonomous information was obtained from 163 autonomous recorder stations.

FIGURE 1: UPPER NORTH ISLAND BITTERN DETECTION RATES (N = 163 RECORDERS)

The high Hauraki detection rates were detected from the large ponded willow areas (IMAGE 1) about the Piako River (Approximately 1,500 hectares). These were mostly developed by duck shooters in the ‘90s. Shooting clubs have spent considerable effort and money creating wetland habitat that benefits both native and introduced water birds. There are over 100 ponds and associated canals along the Piako. Individuals, farmers and clubs such as the Upper Piako Wetlands Management Association help with the maintenance of public access to the wetlands, water level structures and mentoring of junior shooters. They also control pest animals. This season one hunter caught over 3,000 possums and 20 ferrets within the area.

IMAGE 1: SURVEYING BITTERN ALONG A DUCK SHOOTING CANAL, PIAKO RIVER MARGIN WETLANDS

In early May up to 400 shooters retreat into the wetland to shoot ducks. After the annual autumn shooting season the wetland is mostly left to its own devices until the following summer. This quite period coincides with the bittern breeding season. Little is known about the species and the Department of Conservation is in the process of initiating close order studies to better understand its life history. Hopefully a mix of local on the ground knowledge and effort, combined with scientific endeavour can save the species from extinction.

Roadkill (bittern) on the Coromandel is occasionally observed, especially about Whangapoua and Hot Water Beach. Every individual counts as it is thought less than 1000 of these birds remain in New Zealand. Rural landowners can help the species by planting trees on swamp edges adjacent to roads and thus force these lumbering flyers to climb higher over traffic flows. Pond edges and even open drains are good places for young birds to forage.

The breeding season runs between September and December and it is best to stay out of wetlands during this period, as birds have been observed to abandon nests when disturbed. The autonomous survey method does not detect females or provide life history data such as juvenile survivorship rates.

Reference

Stewart, P. 2017. Eastern Coromandel cryptic avifauna species inventory for wetlands of the Waikato Region. Contract report SAS2016/2017-1758 for Waikato Regional Council, Private Bag Hamilton.

Paddy Stewart Red Admiral Ecology www.soundcounts.com