Australian Bittern Acoustics Survey

BARRY SCOTT with PATRICK STEWART (Red Admiral Ecology)

In Spring of 2021 Auckland Council contracted Soundcounts to carry out a baseline autonomous acoustic distribution survey of Australasian bittern (Botaurus poiciloptilus; matuku) at 31 sites across the southern part of the Auckland region as well as on Waiheke and Aotea Great Barrier Islands. The bittern has the highest threat status of ‘nationally critical’.

Data from the acoustic recorders showed that bittern were very sparsely distributed across these sites probably reflecting the very fragmented nature of their remnant wetland habitats. Booming males were detected at just 4 of the 31 sites; two in the Awhitu Ecological District (Big Bay and Rangiriri Creek) and two on Aotea Great Barrier (Kaitoke and Whangapoua). The analysis confirms that at least six males were present and there were no instances of males competing with each other at any of the sites. An audio monitoring survey carried out in 2012 estimated at least six birds were on the island at that time(1).

Other wetland species detected included spotless crake (Porzana tabuensis) and fernbird (Bowdleria punctata vealeae). Here we report the results obtained just for Aotea although the results of the full survey are available from Council(2).

Although the method employed will not have detected all males present, the low number of booming males detected confirms that that this is a species that is just hanging on at Aotea emphasizing the need for wetland restoration and protection to improve safe habitat for this and the other wetland bird species.

References:

1. Geary A, Corin S and Ogden J (2012). Australasian Bittern. Great Barrier Island 2012. Department of Conservation monitoring report.

2. Stewart P (2021). Autonomous acoustic bittern distribution survey in the Southern Auckland region and on Waiheke and Great Barrier/Aotea Islands 2020. Contract report 2021_1 by Soundcounts for Auckland Council.