First-ever Regional Diademed Sandpiper-plover Survey

The Diademed Sandpiper-Plover (Phegornis mitchellii) is a unique but poorly known species of shorebird endemic to the Puna region of Argentina, Bolivia, Chile, and Peru. Here it breeds in peatlands and bogs, locally known as “bofedales” or “vegas,” at high altitudes of up to 4,800 meters. During the non-breeding season, part of the population moves to lower altitudes to escape its snow-covered habitat – however, these migration patterns are not fully understood yet.

The question of whether the species is a sandpiper or a plover has been debated for a long time and is still unresolved. Its slim bill with a somewhat swollen tip resembles that of a sandpiper (Scolopacidae sp.), but other features like plumage pattern, including those of the chicks, resemble more that of a plover (Charadriidae Sp.). And, to confuse things even further, some authors argue that the Diademed Sandpiper-Plover is related to the painted snipes (Rostratulidae sp.). For now, the species has been allocated among the plovers with its own genus Phegornis.

While its categorization is debated by experts, the Diademed Sandpiper-Plover is actually easy to identify: its chocolate brown head with clear white band (the eponymous “diadem,” which can mean a tiara or crown), chestnut hind neck and sides of neck, fine black-and-white barred chest, belly, and flanks, and bright orange legs make it distinctive. But despite these noticeable characteristics, the species is surprisingly hard to find in its habitat and often overlooked. The species is very confident and individuals are not easily flushed.

Due to its rarity, the Diademed Sandpiper-Plover is considered a conservation concern at the global level. Its population size is estimated at fewer than 10,000 birds – but this is a number based solely on expert opinion and not backed up by actual population surveys. A range-wide population survey has never been carried out, but based on scattered observations and restricted habitat preference, its population is likely much lower.

The lack of a clear population estimate for the species limits the identification of key sites on which it depends and, consequently, the development of targeted conservation actions. This is of particular importance considering the advancing mining operations for lithium in the area, which will likely have a negative impact on the species’ preferred habitat. The high volume of water used in lithium mining can result in the drying out of the peatlands and bogs on which the species depends.

But, some good news: supported by Manomet’s strategic launch fund, a first-ever range wide population survey was carried out in collaboration with our local partners in South America to gain insight into a more accurate population size of the species. During a period of 15 days in late November and early December 2023, a total of nearly 80 volunteers in Argentina, Bolivia, Chile, and Peru roamed the peatlands and bogs of the altiplano in search of the Diademed Sandpiper-Plover. A total of approximately 500 sites with potential habitat were surveyed in the four countries, and in 59 sites a combined total of 137 individuals were counted. On average, two birds were found at each site, but at two sites in Bolivia and Chile, a total of seven birds were found, including young immatures. Although the species is hard to detect in its preferred habitat type, we expected to encounter more of these birds. The low counts are alarming and might indicate that the species population is indeed much smaller than previously estimated.

Besides gathering data on the Diademed Sandpiper-Plover, data on other High Andean shorebird species sharing similar habitat were collected, including species the Rufous-bellied Seedsnipe (Attagis gayi), Grey-breasted Seedsnipe (Thinocorus orbignyianus), Least Seedsnipe (T. rumicivorus), and Puna Snipe (Gallinago andina). Also, boreal shorebirds were observed, of which the Baird’s Sandpiper (Calidris bairdii) was the most common recorded in the peatlands and bogs visited.

During the surveys, habitat data was also collected in order to discern the specific habitat requirements of the Diademed Sandpiper-Plover. A preliminary analysis of this data did not show a clear pattern of habitat selection; however, altitude and the presence of clear water from springs appear to be important. We will further explore the data and use the information to develop a habitat model that could help predict both the presence and absence of the species. This will be of use in future surveys, and help to improve ongoing species population estimates.

Special thanks to our local partners CORBIDI (Peru), Chilean Bird and Wildlife Watchers Network (Red de Observadores de Aves y Vida Silvestre de Chile-ROC), Asociación Armonía (Bolivia), and the National Parks Administration of Argentina for helping to execute the regional surveys, which will inform our conservation efforts for these South American endemics going forward.

BONUS: Take a listen to Manomet’s Arne Leisterhuis on a Dutch radio program, discussing this work!