The Pink Heart of the Salar

Andean Flamingos and hidden groundwater at Laguna Chaxa, Chile

In an open wetland, two Andean Flamingos (Phoenicoparrus andinus), known in Chile as parinas grandes, stand together in the shallows. Pressed closely together, their long necks intertwine until they appear joined. Their heads move back and forth around one another in rhythmic unison. The effect is intimate, although its meaning is uncertain. The display may be associated with courtship or help reinforce a bond, but a single observation cannot show whether the birds were a breeding pair. Similar rhythmic head movements have been described in captive Andean and James’s Flamingos, although their precise function remains uncertain. I would describe what I saw simply as a coordinated social interaction.

This encounter took place at Laguna Chaxa, in Los Flamencos National Reserve in Chile’s Atacama Desert. The lagoon lies within the Salar de Atacama, a vast salt flat formed in a closed desert basin, at roughly 2300 metres above sea level. Beneath a cloudless sky and an exposed desert sun, water seems improbable. Rain is rare here, yet flamingos and many other species of waterbirds gather in these shallow wetlands.

Laguna Chaxa is part of the Soncor wetland system (Sistema Hidrológico de Soncor del Salar de Atacama), an important breeding area for Andean Flamingos and a Ramsar site, a wetland recognized internationally for its ecological importance under the Convention on Wetlands. It also supports Chilean Flamingos (Phoenicopterus chilensis) and James’s Flamingos (Phoenicoparrus jamesi). During our excursion we also saw Andean Avocets (Recurvirostra andina), known locally as caitíes; Puna Plovers (Anarhynchus alticola), or chorlos de la puna; Andean Gulls (Chroicocephalus serranus), or gaviotas andinas; and Fabián’s lizard (Liolaemus fabiani), a rare desert reptile endemic to the Salar de Atacama salt flats in Chile

Most of the water sustaining these wetlands falls as rain or snow in the Andean highlands rather than over the salar itself. From there, it seeps into fractured rock and porous sediments and moves slowly underground toward the basin floor. Laguna Chaxa is the visible surface expression of water travelling unseen beneath the desert and forms a closed hydrological system. Water flows into the basin, but because there is no outflow, it leaves through evaporation while the dissolved salts remain behind. Over time, this process has produced the thick salt crust and concentrated brines beneath the salar, including brines rich in dissolved lithium. Where groundwater approaches the surface, springs and shallow lagoons persist. These waters may look nearly empty, but they support microscopic algae and small aquatic organisms. Andean Flamingos feed heavily on diatoms, filtering them from the water and soft sediment with their specialized bills.

The two flamingos stood in only a few centimetres of water. Beyond them, pale water and salt crust stretched beneath an open sky. For those few moments, their intertwined necks and pink plumage marked the heart of the salar.

Sources and further reading

• Rose and Croft: directed social interactions in flamingo flocks
• Ortiz and colleagues: water sources for the Soncor wetland system
• Marazuela and colleagues: hydrology of the Salar de Atacama
• Tobar and colleagues: diatoms in the diet of Andean Flamingos
• Mayr: the evolutionary relationship between flamingos and grebes