The Avon-Heathcote Estuary and the Bromley Oxidation Ponds, Christchurch, New Zealand: An important area for waterbirds.
- Author
- Crossland, A.C.
- Year
- 2010
- Journal / Source
- Stilt
- Volume
- 57
- Pages
- 5-10
- Summary
- Since the mid 1980s, the Avon-Heathcote Estuary and Bromley Oxidation Ponds have been the focus of a waterbird population monitoring programme due to their vast habitat availability. Since 2003, the Christchurch City Council has completed an annual “all species” count in these areas during the peak January-March post-breeding/moult influx period. This paper, written by ornithologist Andrew Crossland, summarises the 2003-2010 dataset from these annual waterbird counts, alongside the monthly shorebird abundance from 1989-1990. 1989-1990 peak waterbird numbers exceeded 20,000 from December through to June, corresponding with typical moulting, post-breeding migration and wintering strategies of many Aotearoa New Zealand waterbirds. During 1989-1990, the highest total counts of waterbirds occurred in December (c. 28,100), January (c. 33,360), and February (c. 28,620), which was found to be typical of the ‘peak period’ in other annual counts. From a total checklist of 136 possible bird species, 44 shorebird taxa were recorded in the Ihutai Estuary area, including 30 waders, 3 skuas, 3 gulls, and 8 terns. Of those, 17 species were native, 5 originated in Australia, and 22 were migrants from the Northern Hemisphere. 6 of the native shorebirds were resident breeders, and 5 of the Northern Hemisphere migrants occurred at least once every 2-5 years. Regarding shorebird abundance, total numbers reached 15,000 from February to May during the 1989-1990 monitoring period. Total shorebird numbers annually exceeded 10,000 birds, although gull numbers declined through the 1990s and 2000s following the closure of refuse tips near the estuary. Maximum wader numbers occurred from January to mid-March when native waders arriving from breeding overlapped with the pre-departure period of over-summering Arctic waders. Overall, the Ihutai Estuary and Bromley Oxidation Ponds supported annual concentrations of 13 waterbird species that met 1% international importance thresholds determined by Wetlands International. 13 species found in the area were also considered nationally critical, endangered, or vulnerable.