This discussion was first published as part of the 2013 Red List update, but remains open for comment to enable reassessment in 2015.
Brown Teal Anas chlorotis is endemic to New Zealand, where it was once widespread in the North, South, Stewart and Chatham Islands, but its range is now much reduced. It is currently listed as Endangered under criterion B1ab(iii) of the IUCN Red List, on the basis that it had a very small range, it was found at ≤5 locations and the population was in continuing decline owing to predation by introduced mammals. However, intensive management has halted the decline and populations are now increasing, with several new populations being established.
The current strongholds are on Great Barrier Island, Northland and Coromandel. On Great Barrier Island, there were 1,300-1,500 birds in the early 1990s, declining to little over 500 in the early 2000s and increasing to over 600 in 2004, and at Mimiwhangata and Teal Bay on the east coast of Northland, the population declined by 65% in the period between 1988 and 1999 to c.100 individuals in 2001 before increasing to nearly c.350 by 2007 (Williams and Dumbell 1996, M. Williams in litt. 1999, Parrish and Williams 2001, Roxburgh 2005, S. Moore and P. Battley in litt. 2012). The re-introduced population in the northern Coromandel numbered c.500 individuals in early 2008, and is now estimated at c.700 birds (N. Hayes in litt. 2012), although its estimated Area of Occupancy is only c.300-500 km2 (Callaghan et al. in prep). After a study on Great Barrier Island indicated that the population was halving every 4.1 years and could rapidly decline to extinction, intensive management was initiated which has seen populations rising again (Ferreira and Taylor 2003, Roxburgh 2005, Hayes 2006, Sim and Roxburgh 2007). Small islands where birds have previously been introduced and persisted for one to two decades may be too small for long-term survival, and some of these populations appear to be approaching extinction; however, the overall population trend is now positive (M. Williams in litt. 1999, Roxburgh 2005, Sim and Roxburgh 2007). New populations have been established at Tawharanui, Cape Kidnappers and Tuhua Island (A. Booth et al. in litt. 2012). The re-introduced population at Cape Kidnappers is now estimated to number c.135 birds (Booth 2011). By 2010, an estimated 1,700 birds were present at the three main sites (Great Barrier Island, Northland and Coromandel) and including the newly established populations, this figure was suggested to be in excess of 2,000 in 2010 (A. Booth et al. in litt. 2012). If these trends are confirmed, the Brown Teal would qualify for downlisting on the basis that it no longer has a very small range, the species’s Extent of Occurrence (EOO) and Area of Occupancy (AOO) are no longer continuing to decline, it is present at approximately 7 locations and the population has been increasing since 2003, following the establishment of new populations. If the number of mature individuals does approach as few as 1,000, and the population is restricted to 7 locations, this species would qualify as Near Threatened under criterion D1+2 on the IUCN Red List.
Further information is requested on this species’s population size, the size of the largest subpopulation, population trends and distribution. Comments on the proposed downlisting are welcome.
Ferreira, S. M. and Taylor, S. (2003) Population decline of brown teal (Anas chlorotis) on Great Barrier Island. Notornis 50: 141-147.
Hayes, N. (2006) Brown Teal released at Port Charles, New Zealand. TWSG News: 16-18.
Moore, S. J. and Battley, P. F. (2006) Differences in the digestive organ morphology of captive and wild Brown Teal Anas chlorotis and implications for releases. Bird Conservation International 16(3): 253-264.
Moore, S. J., Battley, P. F., Henderson, I. M. and Webb, C. J. (2006) The diet of Brown Teal (Anas chlorotis). New Zealand Journal of Ecology 30: 397-403
Parrish, R. and Williams, M. (2001) Decline of Brown Teal (Anas chlorotis) in Northland, New Zealand. Notornis 48: 131-136.
Roxburgh, J. (2005) Brown Teal (Pateke). Wingspan 15: 15.
Sim, J. and Roxburgh, J. (2007) Brown Teal bouncing back. Southern Bird: 8-9.
Williams, M. and Dumbell, G. (1996) Brown Teal (Pateke) Anas chlorotis recovery plan. Wellington, New Zealand: Department of Conservation.