Life, death and love on Onetangi

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    Two celebrity summer blow-ins have returned to Onetangi Beach to raise a family, without needing to dip a toe in the Waiheke Accommodation Facebook page. 

    Hurrumph! Considering their new digs are absolute-absolute beachfront – within an airy bespoke cube with all-day sun – some might feel the couple are molly-coddled attention-seekers.

    Mind you, they have been coming here for a while. 

    Wai and Heke are endangered New Zealand dotterels, and their ‘house’ is an enclosure designed to protect their nest. This seems, to be fair, only fitting for a species older than the beach they are nesting on. (Which isn’t hard, as Waiheke beaches are very young in geologic terms.)  A phylogenetic analysis by University of Otago researchers suggests their distant ancestor, a different bird, arrived in New Zealand in the Middle Miocene. Something looking like a New Zealand dotterel – its immediate ancestor – probably evolved in the Late Miocene, over five million years ago. 

    Wai and Heke are Northern New Zealand dotterels, Charadrius obscurus aquilonius, and scientists think they diverged from Southern New Zealand dotterels, Charadrius obscurus obscurus, in the Middle to Late Pleistocene, tens of thousands of years ago.

    The analysis of these shorebirds has revealed a poignant detail. Only two ends of the ancient New Zealand dotterel ‘continuum’ survive, in the upper North Island, and on Stewart Island. Something happened to the dotterels living in the rest of Aotearoa. 

    What can we learn about these ghost populations? How did they adapt to changing eco-systems over time? How were they different from surviving dotterels?

    “To ensure the best ongoing evidence-based conservation management [of living dotterels], ancient DNA research is needed throughout their prehistoric and historic range to resolve their evolutionary history,” Director of Otago University’s Palaeogenetics Laboratory, Dr Nic Rawlence, tells me. 

    Dotterel fossils, lying in sand dunes and museum drawers, have much to tell us. Buoyed by the success of a similar study into Otago and Foveaux shags, Dr Rawlence’s lab is looking for a postgraduate student to study ancient dotterel DNA.

    There is something mind-blowing to me about the thought that these tiny dotterels are older than Onetangi Beach itself – older, even, than Waiheke – and would once have flitted over an unimaginably different world. During the Last Glacial Maximum (LGM), 17,000 years ago, the sea level was some 125metres lower than it is now, as so much water was hoarded by ice sheets. The land which became Waiheke was miles from the shore, surrounded by a lowland plain. Dotterels once nested on a far off beach, beyond where Great Barrier Island is today. As ice sheets melted at the end of the LGM, Waiheke Island was created by rising seas sometime after 7,000 years ago. 

    Over thousands of summers the dotterels, like other shorebirds, followed the coastline as it surged inland.

    For most of their existence, these beaches were primo real estate for shore birds, who faced few threats except for predatory black-backed gulls and freak storm waves. Just how nurturing New Zealand’s coastlines and wetlands once were can be seen by the species which thrived here — 161 of New Zealand’s 252 native birds (living and recently extinct) are wetland birds, shore birds or seabirds, making Aotearoa one of the great squawking, peeping sea bird capitals of a world in which 90 percent of bird species are land birds.

    Today, many wonder why [dotterels] choose such a vulnerable place to nest. But New Zealand beaches have only been unsafe for dotterels for the blink of an evolutionary eye, not a long enough length of time to allow them to adapt. For millions of years of dotterel evolution, the shore was a place a young dotterel family could thrive. Birds, chicks and a nest constructed in a scrape of sand became, over the millennia, spectacularly well camouflaged to hide them from flying marauders. 

    Since the human sponsored arrival of egg and chick snuffling stoats, rats, cats, dogs and hedgehogs, New Zealand dotterel populations have cratered. Those that survive do so mainly thanks to the unflagging diligence of conservation groups and bird lovers. Today, the remnants of a species which once flourished from here to Rakiura needs all of us to help them survive.

    At Onetangi, the volunteer Dotterel Guardian Group have already seen three eggs and two nests disappear in the last few weeks. 

    “Last year, we had only three successful chicks out of 24 eggs [on the island] and the biggest issue is dogs,” dotterel guardian Gabrielle Young tells me. 

     Eggs aren’t as cute as a live chick [like last year’s media star, Storky] – but the stats show how difficult it is to get to that point.”

    New Zealand dotterels once saw a very different Waiheke.  Having destroyed their ecosystem, keeping our pets indoors, on a leash or simply taking them to the other end of the beach during the nesting season seems not only ridiculously easy, but the very least we can do. •

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