Efforts to save the critically endangered shore plover from extinction in New Zealand have suffered a major setback: nearly 60 of the birds have died due to unknown causes, reducing the world population of the species to just 200.

Shore plovers (also known as shore dotterels or Tuturuatu, Thinornis novaeseelandiae) lived on both of New Zealand's main islands before European settlers introduced cats and rats that nearly eradicated the species during the nineteenth century. Luckily a small population of 130 birds survived 800 kilometers away on one of the country’s smaller islands, South East Island (also known as Rangatira), from which a captive-breeding program began in the 1990s. The New Zealand Department of Conservation (DOC) has spent the last 20 years establishing small, additional populations on other New Zealand islands, including Portland Island (a.k.a. Waikawa), where the dead birds were found at the end of 2012.

Until this unexpected tragedy the birds on Portland had been doing so well that some of the eggs laid there were being moved to other predator-free islands to fortify additional assurance populations. "This has a huge impact on the viability of the species," DOC team leader for shore plover recovery on Portland Island said earlier this month in a prepared release.

Portland Island is a privately owned sanctuary that to the best of the DOC's knowledge does not contain rats, cats, stoats (a type of weasel) or other bird-killing predators. DOC has now set up cameras and recently brought in dogs capable of sniffing out any stoats, but nothing has turned up. The department is also performing disease screenings and autopsies on the dead birds. At least one previously established island population failed when the birds contracted a disease called avian pox.

The remaining 20 shore plovers on Portland Island are now being closely monitored, while 12 eggs found at the end of last year have been moved to two other wildlife centers for incubation before being released on Mana Island, which should take place in March. Additional populations are also maintained on Rangitoto and Motutapu islands, which the DOC cleared of predators in 2011 before moving 17 plovers there in 2012. Some of the released birds can be seen in this video:

Most of the island reserves are far out to sea, too far from the mainland but close enough that the birds can fly from island to island. Mana Island, however, is just three kilometers from New Zealand's north island and the birds have been known to fly back to the mainland. In 2011 a group of 30 shore plovers flew from Mana Island to a mainland beach near Wellington. They can be seen searching the tide for crustaceans in this video:

The DOC has previously asked anyone sighting shore plovers on the mainland to report them so the department can try to recapture them and remove them to safety.

Photos: An adult shore plover and a chick, courtesy of the New Zealand Department of Conservation