Incredible footage of Birds of Paradise

Just mind-blowing. A short film about the Birds of Paradise project run by the Cornell Lab of Ornithology. Even if you’ve seen Attenborough’s films a hundred times this will still have you gazing in awe. Thanks to the great blog Tough Little Birds, about the realities of undertaking scientific research (focused on Dark-eyed Juncos), for bringing this to my attention.


The best commute in the world, and searching for a subflava in a gold mine

One of the main questions we were investigating was the importance of rivers in structuring populations of our chosen antbird species (the Peruvian warbling antbird Hypocnemis peruviana, yellow-breasted warbling antbird H. subflava, and the chestnut-tailed antbird Myrmeciza hemimelaena). In other words, how connected are individuals on one side of a river with those on the other? Are they equally likely to mate with those on near and far sides of a river? And if there are river effects, do these differ between species, depending on their ecology and behaviour? (These are questions at a local scale, that form part of broader questions relating to the diversification of Amazonian birds; more background information about the project is given in an earlier post.)

It is possible to look at population connectedness by using genetic analysis of blood samples. In a technique analogous to DNA fingerprinting, individual patterns of genetic markers can be described for each bird. Instead of using these to work out the relationship between two birds, the distribution of markers within a whole population can be assessed. Clusters in the data reflect groups of individuals that are more closely related to each other than to other groups. These clusters can then be matched with their geographical location, and if they fall on opposite sides of a river, then this would suggest that the river is a barrier to gene-flow (interbreeding) between populations.

Our analyses are still not complete, so the final part of the story is not yet known, but all this meant that we needed to cross the river to collect samples. Instead of setting off into the forest in the morning, we would descend the 250 stairs from the high upland terra firme, down to the riverbank. We’d scramble into a boat, and if the engine started quickly, we’d be on our way in the dawn twilight, watching the sky change colour, and the mist rise from the river. It was only a short journey down river, either 10 minutes to the village of Boca Amigos, or 20 minutes to a satellite station belonging to CICRA, known as CM1. But it was a beautiful way to travel to ‘work’, one that I never failed to appreciate, and one that was always different depending on the weather and light.

Boca Amigos is a small village, home to a handful of families, with most houses also seeming to double as a shop or bar. There’s a small school, and a football pitch, as can be found in every Peruvian community no matter how small. We’d arrive before many people were up, and would quietly walk between the houses to reach the trails into the forest beyond.

The journey to Boca, and our exploration of the surrounding forest, also brought home one of the less beautiful aspects of life in the Amazon: gold mining. We would pass mining dredges on our way downriver (in fact we could hear them, generators running late into the night, from CICRA).

The price of gold keeps on rising, and the opportunity to make a decent living in the jungle by mining gold continues to attract migrants, particularly from the Andes. The work is tough and relentless, but profitable. It results in huge mounds of gravel, deforestation, and leaves behind desolate expanses of bare ground, and pits filled with polluted water.

The cheapest and easiest way to extract gold is to use mercury. Mercury is therefore being constantly washed into the river, entering the forest ecosystem and food chain, and is likely to be having a terrible effect not only on the forest species but also on human health. The whole issue of mining is complex and controversial: the needs of people and the protection and conservation of the rainforest requires a careful balance, which has not yet been reached. It is an issue right across Amazonia. Although the blue-tarpaulin covered mining camps that we walked through behind Boca were small-scale, some mining operations have an impact on a much greater scale, and anyone who has flown between Cusco and Puerto Maldonado will have seen a huge scar in the otherwise mostly unbroken rainforest canopy.

Mist-netting around a gold mine was not something I had expected when I set off for Peru. It was shocking to see the devastation of the mines. We would climb over huge felled trees, and navigate around the pits, trying to hear our species singing above the noise of the generators.

We found birds adjacent to the mines, and were defecated on from a great height by a group of howler monkeys who objected to our presence, so jungle life continues in the adjacent forest. This gave some hope that once abandoned, the mines could be reclaimed by the forest. But I have no idea how long it will take for all traces of the mines to be gone, as the ground has not simply been cleared, but excavated, and the effects of mercury – invisible and far-reaching – are likely to persist for much longer. Working there also gave us a more personal perspective on the whole situation. We exchanged buenos dias with miners as they were preparing their breakfast, bemused at the site of us with our microphones and mist-netting gear, and they came to our rescue when our boat engine wouldn’t start. It is easy to say that the mining should be stopped – and heartbreaking to learn about the extent of the destruction across Peru and beyond – but is not easy to achieve, especially whilst also ensuring the livelihoods of those who currently depend on it. A much more in-depth and eloquent report on gold mining can be found on the Smithsonian magazine website, and an award-winning new film, Amazon Gold, documents the destruction of the Peruvian rainforest for gold. The trailer below is well worth a look.

Why are there so many birds?

The main question behind my PhD research is why, and how, are there so many species in the Amazon rainforest. There really is a ridiculous number of species. Hundreds of bird and tree species can be found at single sites, dwarfing the numbers found in whole countries in Europe for example. The Amazon is not alone in being highly biodiverse, many tropical regions harbour vast numbers, but the Amazon and Andean lowlands have the greatest number found anywhere on earth.

It is mind boggling to try and grasp the magnitude of the diversity: whereas you’d be lucky to see one or two dozen bird species in your garden at home, in the rainforest hundreds of birds live in the same patch of forest. Many have had their minds boggled trying to work out why it is that diversity increases as you travel from the poles to the equator. And more still have concentrated on tropical rainforests, enthralled by the conundrum of so many species evolving in the first place, and then being able to coexist.

The particular hypothesis I am interested in is one that has roots in the earliest explorations of Amazonia. Alfred Russel Wallace, now celebrated for his insights into the theory of natural selection, set out in 1848, at 25 years old, to explore the Amazon rainforest. He noticed that some species were found on one side of a river, but never the other. The rivers themselves seemed to be the boundary, the limit of a species’ range. Since then numerous biologists have explored the extent to which rivers may limit species ranges, and more crucially, the extent to which they actually drive speciation (the evolution of two new species from one) or simply limit the distribution of species that have evolved elsewhere.

Chestnut-tailed antbird.
Photo credit: Will Minehart

My PhD tried to unravel a tiny fraction of the story, by looking at how populations of different species are structured across rivers. I was in Peru to get blood samples from my study species, so I could work out from genetic analyses the extent to which populations on opposite riverbanks were connected with each other. If rivers are barriers between populations, meaning that birds on one side very rarely mate with birds on the other, then with a great deal of time, these populations may evolve to become distinct species. The rest of my time was spent behind a desk back home, looking at hundreds of bird range distribution maps, and how they related to the many rivers that run through the Amazon basin.

Birds may seem a daft choice for investigating the ‘river barrier hypothesis’, as they have wings. But many tropical birds are surprisingly bad at flying across open spaces such as rivers. My study species the antbirds prefer to stay in the dark dense understorey, and therefore are some of the most likely to be affected by river barriers.

Although my research questions focus on the evolution of Amazonian diversity, they are part of a much broader set of questions trying to get at the root of how and why species evolve into new species. These PhD students studying coral ecosystems are dealing with the same evolutionary questions, and do a great job of explaining their research. They also convey a little of the frustration in carrying out field and lab work:

This is quite unrelated except as another brilliant example of creative science communication, prizewinning no less, by my talented colleagues at the EGI. Original music by Stuart Noah and choreography by Cedric Tan, with a cast of PhD students…