This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: On open beaches, gravel riverbeds and bare volcanic plateaus, banded dotterels—or double-banded plovers, as they are called in Australia—are a familiar and much-loved sight across New Zealand, the only country where these charismatic plovers breed. While some remain year-round, an estimated 70% make a rather unusual migration: Instead of flying north to warmer climes, as most migratory birds do, they head west, almost 3,000 kilometers (1,860 miles) across the Tasman Sea, to winter in Australia.
A new study by the Department of Ornithology at the Max Planck Institute for Biological Intelligence (MPI-BI) suggests this age-old ocean crossing could disappear due to climate change. An analysis of observations from the citizen-science platform eBird shows that the birds arrived in Australia about four days later each year on average between 2014 and 2025. With no clear change observed in their date of departure back to New Zealand, their total estimated stay on the Australian nonbreeding grounds fell by around a quarter in just over a decade.
The research, published in the journal Ibis, links the delay to a southward shift in the winds circling Antarctica, driven by human-caused global warming. This has made calm, mild fall and winter weather increasingly common in New Zealand since the 1950s. "The rapid pace of this change raises critical questions about where it could lead," said Bashar Jarayseh, first author and a doctoral student at MPI-BI.
"Most banded dotterels that migrate come from harsher inland alpine habitats, escaping the New Zealand winter for milder conditions in Australia. But the ocean crossing is dangerous, and if their stay in Australia shortens, the benefits of migration may shrink while that risk remains, so within a few decades migrating individuals may be at a disadvantage. "We predict that this could eventually lead to a behavioral extinction of migration, with the entire population remaining in New Zealand.
That would leave the species more vulnerable, for instance to a single, unusually harsh winter." The researchers used a map of the birds' Australian nonbreeding range, dividing it into areas of about 23,000 km2 (8,900 square miles). For each of these areas, they tracked how sightings in eBird built up and tailed off to estimate when the birds arrived and left again. This approach put the estimated average stay at 173 days in 2014 and 129 in 2025, a reduction of about 25%.
The team then compared each year's arrival date with monthly readings of the Southern Annular Mode, a broad climate index for the region, and found the birds arrived later in years with milder weather in New Zealand toward the end of their breeding season. "A lot of what we know about climate change and migration comes from the Northern Hemisphere, where birds are reaching their breeding grounds earlier in spring. Our results add a case from the less-studied Southern Hemisphere, where New Zealand banded dotterels are instead reaching their wintering grounds later each year," said Luke Eberhart-Hertel, a co-author of the study at MPI-BI.
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