Tropical River Island Pioneers

Before morning, we dock the canoe and walk half an hour on boardwalks to the lodge's docks, where a boat captain awaits us.  Several long days, the heat, and all that trudging through rainy forests has made me deliriously tired. 

But once the motorized canoe disembarks, and we are screaming down the Napo River, my weariness fades, and I am struck with an energy whose origin I cannot immediately explain.

The Napo River is Ecuador's biggest contribution to the Amazon.  It winds, twists and flows from the valleys of the Andes through the lowlands of the Ecuadorian Oriente.  Throughout its length, the Napo River is, perhaps more than any other large Amazonian River, riddled with islands and sandbanks, giving the river a geographic character like a complex archipelago. Down here in the lowlands it is a muddy whitewater river, carrying Andean sediment, and that mud is the raw material of every island. The island specialists I've come to see are mostly birds of these sediment-heavy rivers, not the clear or tea-colored blackwater rivers, where islands are fewer and far more stable.

We are motoring towards the immense Yasuni National Park, stopping along the way at several islands.

A Sandbank Full of Birds

We pull up to an island with a wide, sandy beach, which is lined first by layers of grasses and shrubs, and then towards its interior, inhabited by cecropia trees and fast-growing palms.

You can’t escape the sheer amount of birds on this island –martins and nightjars among the grasses of the wide sandy plains for example, and hummingbirds and spinetails in the denser shrubs at the center of the island. Some of these birds live almost nowhere but on river islands like this one: Castelnau's Antshrike, White-bellied and Parker's Spinetails, Olive-spotted Hummingbird, Black-and-white Antbird, Lesser Wagtail-Tyrant, River Tyrannulet. Birders come to the Napo just to hop islands looking for them.

Although the Amazon has the largest avian diversity in the world, the birds aren't exactly abundant.  In fact, the Amazon has nothing on my backyard on an early spring morning.    Why then, is this tiny river island teeming with bird life?

I walk with Carlos and Pablo through the grasses of the island, and I realize the source of my unexpected energy.  The weather out here on the river itself is a perfect seventy-eight degrees.  There is a light breeze, no clouds in the sky.  This is the weather of the Open Amazon basin rivers, all year round.  So delightful, and this is our plan for the whole day, just me, the captain, and my two guides, just visiting islands and floating through the breeze.

Some travelers believe the Amazon holds the most perfect weather in the world.  For me, there is something about open blue sky without shade that captures me, sucks me in. 

Three Boys in the Grass

In the grasses I am surprised to find three boys, aged about three years apart.  They are playing joyfully, digging in the sand, following us, hiding in the reeds.  They are here alone without supervision.  Their canoe is parked on a sandbank on the other side of the island. But where is their village?  There is only jungle on either side of the river. 

For many in my generation and before, the clearest memories of boyhood were like this one; long hours of independence and friendship, with the landscape acting like a big white canvas, waiting to be painted.

I wander off by myself, and am surprised to again meet some people, strange since there is little evidence of humanity for miles along this river.  A birding guide and his clients from Spain.  By a bizarre coincidence, I had met this guide on the airplane from Quito.  He had just returned from his first time traveling Ecuador as an independent guide. We talk for a few minutes before Pablo emerged from the woods, stunned and surprised, both that his younger brother is here on this tiny island, and how on Earth do I know him?

Pablo and his brother spent their childhoods much like the three children hiding in the grasses, with the Napo River and all its complex geography as their blank canvas.  As adults, both earn their living by doing what they loved as children.

Temporary Islands

When we renew our focus on the island itself, I can see that the island is little more than a sandbank, which by the shifting nature of the Napo River, was able to make its hold against the river through the flood season. 

Often, the islands form as deposits of sand build-up along the curves of the river.  Sometimes, the islands are the results of the river itself subtly changing course, cutting slices out of riverside bends.

River islands on the Napo are temporary.  A strong storm, a rainy season, the shifting course of the river itself can all tear any of these islands apart in an instant.  Why have so many birds evolved to take advantage of such a peculiar, dangerous habitat?

Back home in Oregon, I can walk a quarter mile from home and run into dozens of habitats, each of which I might recognize as being suitable for a certain kind of bird.  Even the way the light falls on a place, the size of the branches, the amount of moss, the presence of steep cliffs, the species of tree, the presence of dense shrubs nearby, and so on and so forth, can tell me an abundance of information about what that might be fluttering in the distance.

But the Amazon, to us North Americans, seems unendingly the same.  Intense and awe-inspiring, yes, but not with the variation that comes with our North American habitats.

Some birds in Oregon, such as the diminutive wrentit, cannot be found in the state of Washington, simply because the mouth of the Columbia is too long a flight for a bird that rarely flies more than a few yards and seldom leaves thick brush.  In the Amazon, rivers are a natural part of the explanation for the vast avian diversity here.  Alfred Russel Wallace noticed this in 1852, when he found different monkeys on opposite banks of the Amazon's big rivers. Rivers aren't perfect walls: when researchers released birds over open water, strong-winged canopy birds crossed easily, while antbirds and wrens failed more often than not. But for many understory birds, which rarely fly far at all, a wide river is a nearly impenetrable border.  As rivers change course and form new paths through jungle, populations get split into two, creating the perfect opportunity for a species to split as well.

It is not true that all of the Amazon is the same.  There are indeed very distinct habitats, simply unrecognizable to us.   So, while rivers are important to the story of birds in the Amazon, river islands, which are fiercely different from any other type of habitat in the Amazon, play a distinct habitat role.

Young Islands and Old

We leave this island and hop to another.  This island has survived for over two decades, and so while the former island was composed mostly of reeds and grasses, this one has established a forest of fig trees and cecropias; pioneer species that have themselves cut their own evolutionary niche.  These trees specialize in taking root before anything else does.  They live fast, grow fast, die fast.  Their strategy is not to find permanent settlement, but to keep their species planted in the niche that they are best suited for. The islands age in a predictable order: bare sand, then grasses, then thickets of cane and Tessaria shrubs, then Cecropia forest, and at last a mixed floodplain forest like any along the riverbank.

Curiously, the eighteen or so bird species that specialize in river islands prefer the younger islands, composed mostly of cane, grasses and shrubs.  Older islands, with larger and more established trees, begin to collect birds that you might find along the river edge.  But why are the populations densest and most diverse in the simplest habitats?  Those reeds and grasses, adjacent the lush river water, attract a bounty of insects, and perhaps fewer of the predators that raid nests on the mainland, though no one has really proven that part.  A species which can evolve to inhabit the fast-paced and dangerous lifestyle of an island always at the edge of being swept away has a special advantage — a bounty of food like nowhere else in the Amazon, with less trouble from snakes, monkeys and other nest robbers. 

River island pioneers are adapted to moving along the rivers from island to island, so their habitat stretches over thousands of miles of Amazonian waterways. It is tempting to think such mobile birds buffered the Amazon against past climate swings, reseeding it after droughts. The genetic evidence tells a more interesting story. DNA studies of floodplain birds, Castelnau's Antshrike among them, show their populations rose and fell with the rivers themselves: in drier glacial times the floodplains shrank and populations were cut apart and began to diverge, and over the last twenty thousand years, as rising seas and a stronger monsoon piled up sediment and built new islands, the island birds spread fast and long-separated populations met again.  So while these tiny river islands may be the least likely place to look for life, they may, in part, help explain why there is so much of it here.

Oil on the Napo

We continue downriver, into the water that borders the Yasuni National Park, believed by some scientists to be the most biodiverse place on Earth. A 2010 study found that Yasuni holds world diversity records for amphibians, reptiles, bats and trees, with more than 650 species of trees in a single hectare, and perhaps 100,000 species of insects in that same hectare.  Along the way, we see only a handful of small fishing canoes.  More regularly, we see oil boats.

Oil is everywhere along this river, which holds vast petroleum reserves. Texaco, which opened Ecuador's Amazon to drilling, pulled out in 1992; the boats and flares out here belong mostly to Ecuador's state oil company, now Petroecuador.  Fires rise from the jungle and barges ply the open water, from extraction site to extraction site. But the history of conflict between oil and indigenous populations in the Ecuadorian Amazon, the pressure of international environmental groups, and a President, Rafael Correa, who had made a public cause of how oil interests exploited indigenous populations, has advanced a peculiar strategy to keep the rich Yasuni free of oil extraction.  The Yasuni-ITT Initiative, launched in 2007, offered to leave untouched the oil beneath the park's Ishpingo-Tambococha-Tiputini (ITT) field, about 20 percent of the nation’s proven reserves, in exchange for international payments of roughly half the oil's value, some $3.6 billion. When I was here, it was still gaining traction and attention worldwide. It never came close: of $336 million pledged, only about $13 million arrived, Correa abandoned the plan in August 2013, and drilling in the ITT field began in 2016. Then, on August 20, 2023, Ecuadorians voted by nearly 59 percent to stop drilling in the ITT block, and the Constitutional Court gave the government one year to shut it down. That deadline passed long ago: three years after the vote, only a fraction of the block's roughly 250 wells have been closed (the government says under a quarter, Waorani leaders say closer to a tenth), and some 40,000 barrels a day still flow.

When we again depart the boat, we walk into the vast wilderness of the Yasuni.  Moist, humid, dark, filled with life.  After climbing a ridge, we find a fresh cougar print on the trail.  Vines filled with flowers dangle from trees whose tops we cannot see.  Up there, we can hear macaws chattering. We hear noise everywhere, and the only thing we cannot hear is the sound of oil boats plying the water along this vast island of diversity.