There are few natural sights more remarkable than a collpa, or a macaw clay lick, covered very early in the morning with dozens of brightly colored macaws, parrots, and parakeets jostling with each other for access to the mineral-rich clay mud. The world’s largest collpa is near the Tambopata Research Center, on the Río Tambopata, about a seven-hour boat ride upstream from Puerto Maldonado.

At dawn, as many as 600 birds perch on surrounding trees before they cautiously descend to the riverbank. By 7 a.m. the show is over. There are similar but smaller collpas spread throughout the Parque Nacional Manu and the Reserva Nacional Tambopata.

Why do these birds eat the clay? As scientists have recently discovered, the answer has to do with the fact that many jungle fruits contain toxins that give unripe fruit a sour taste. The toxins are designed to prevent predators from eating fruit until the seeds are fully developed. But the minerals contained in the clay eaten by macaws, parrots, and parakeets neutralize the toxins, allowing the birds to digest unripe fruit and giving them a competitive advantage over monkeys and other fruit-eating animals.

The most common macaws found in the Peruvian Amazon are the red-bellied macaw, which is mostly green with a dullish yellow color on the underside of its wings and tail, and the blue-and-yellow macaw, which is bright blue on top and yellow underneath.

Less common are the chestnut-fronted macaw, which is mostly green but with a reddish color in the underside of its wings and tail; the scarlet macaw with yellow median upper wing coverts; and the red-and-green macaw, which is deep scarlet with green median upper wing coverts.