For 87 years after the first specimen was collected, nobody was entirely certain whether the Campbell Island teal was a real species or a mislabelled stray from the Auckland Islands 270 kilometres away. The question was resolved in 1973 when a small population was discovered on Dent Island, a 23-hectare islet off Campbell Island that had remained free of Norway rats. There were perhaps a dozen birds. The species existed, but only just, and the arithmetic of a dozen individuals on 23 hectares is not a comfortable place from which to begin a recovery programme. The margin was thin. The risk was absolute. The species hung by a thread.
The Campbell teal is a small, flightless, nocturnal duck. Males are dark sepia with green iridescence on the head and a chestnut breast. Females are uniformly dark brown. Both have white eye-rings that sit wide on the face and give them a look of mild, permanent attention. The wings are vestigial and entirely decorative in terms of flight. The natural habitat is Poa tussock grassland, ferns, and megaherbs, with rocky shorelines and peaty streams providing foraging corridors. The species also uses the burrow networks excavated by petrels nesting across the island, moving through them as pathways and for shelter, an unusual strategy for a duck that reflects a long shared evolutionary history with those seabirds. The adaptation is specific. The niche is narrow. The survival is precarious.
Eleven birds were removed from Dent Island in stages and placed into a captive breeding programme at Pukaha Mount Bruce. In 1999 and 2000, 24 captive-bred birds were released onto Whenua Hou off Stewart Island, already managed as predator-free habitat for
kākāpō. That population established and bred without difficulty, providing a second insurance population outside the subantarctic. The effort was sustained. The result was positive. The backup was secured. The species was no longer confined to one spot. The risk was spread. The future was brighter.
The major intervention came in 2001, when Norway rats were eradicated from Campbell Island in one of the largest island rodent eradications ever attempted at the time. The operation required dropping brodifacoum bait across the entire 11,000-hectare island by helicopter. Between 2004 and 2006, 150 captive-bred and Whenua Hou-raised birds were released onto Campbell Island itself. The population has grown, and the species is no longer confined to a single 23-hectare islet. The return was successful. The habitat was ready. The birds adapted. The numbers increased. The isolation ended.
Current estimates put the total at 800 to 1,000 mature individuals. The risk that remains is straightforward and difficult to fully eliminate: a ship arriving at Campbell Island with rats aboard. The teal cannot fly away from that. Any reinvasion on an island it cannot leave would undo most of what has been achieved since 1973, and it would do so quickly. The threat is external. The vulnerability is internal. The flightlessness is a liability. The protection is human. The vigilance must be constant. No one told it otherwise.