A working day started soon after 4am, so we could be at our chosen spot by sunrise. In the dark, I would scan the floor for dangerous creatures, shake any more from my clothes, and tip my boots upside down just to make sure before putting them on. Despite my fears of spiders, snakes, scorpions, cockroaches, centipedes…I think I only ever found a frog, in a boot, once.
I’d meet my field assistant in the comedor, and we’d quietly go through our morning routine, filling water bottles, stocking up on breakfast snacks, and then assembling the various bits and pieces we needed in the field: a toolbox full of needles, tubes of ethanol, capillary tubes, bird rings, rulers, and scales, speakers, mp3 players, mistnets, bird bags, bamboo poles, machetes, microphone and sound recorder.
Setting off into the forest, the low light – if any at all – would turn to almost complete darkness as we entered the trail system and walked under the canopy. It took a while for the light to reach us through the trees, so we made our way by the light of our headtorches, which would catch the blue shine of spiders’ eyes on the forest floor.
It felt exciting to head off into the forest while many were still asleep at the station, seeing the first of the new jungle day, and enjoying the sound of the nightshift merge into the dayshift. It also meant we got to walk face first into all the spiders’ webs that had been constructed across the trails over night. We’d walk waving a stick or machete in front of us to catch the webs first.
We were out to find three particular species of bird. All three are antbirds, small, insectivorous birds that lives in the understorey of the forest. One species, the chestnut-tailed antbird (Myrmeciza hemimelaena) barely gets above the ground, zipping between dense tangles of vegetation half a metre off the forest floor. The other two are usually found between 1–4 metres off the ground; one, the yellow-breasted warbling antbird (Hypocnemis subflava) has a tendency to be found in bamboo patches, while the other, the Peruvian warbling antbird (Hypocnemis peruviana) is usually in the broad-leaf forest matrix. Finding them was easy, because they are all highly territorial, defending their patch of forest against intruders. We could mimic an intruder, by playing the song of each species on our speakers, prompting an angry, defensive bird to head in our direction. Generally, this would bring both male and female birds towards us, as they defend their territories together as a pair, and sing duets to do so. The challenge once we knew where they were was to work out where to put a mist-net with the highest chance of them flying into it.
The trick was to anticipate which branches or tangles of vegetation would be most appealing to the birds, and the route they might take from one to another, and to put the net between them. Sometimes the trail itself was suitable, other times we’d need to clear enough space to fit the 12 metre long net. We’d loop it onto two bamboo poles, pull it taught, and tie the poles to suitable trees nearby. The net extended from the ground up to almost 4 metres, and consisted of 4 parallel pockets running the length of the net. It was hard to see, and if positioned out of the light would be almost invisible, to us as well as the birds (and on one occasion a furious large Amazonian squirrel that thrashed about until it thrashed itself free). The speakers would be placed on the ground in the middle of the net, with the appropriate song playing on a loop. When a bird flew into the net, it would fall into the pocket just beneath it, unhurt but slightly tangled. We’d keep a close eye on the net and quickly extract a bird once it was caught. It would be put into a small cloth bag until we were ready to process it a few minutes later.
So that we would know if we saw, or caught, the same bird again, we put small rings on their legs – one metal ring with a unique number, and then three coloured rings in a unique combination. I’d measure the length of the wing, tarsus, beak, and weigh the bird, as well as take a couple of drops of blood from the vein under the wing for genetic analysis. Within a few minutes the birds would be released back into its territory.
Taking a blood sample from a chestnut-tailed antbird. Photo credit: Frances Buerkens http://www.francesbuerkens.com
But it wasn’t always so simple, and we must have spent many hours watching birds come towards the net, fly over it, stay just next to it, and not fly into it. There was nothing we could do but watch, and will the bird to fly where we wanted it to. Sometimes we’d re-position the net and try again, sometimes it would be so close for so long that we couldn’t give up, but sometimes the birds were just not going to fall for our tricks. Add to that a swarm of ants, a nest of tiny ticks, bamboo spikes or wasps and a day in the field was often a lesson in patience and calm. We’d head back for lunch in the heat of the day, brandishing hard-won blood samples, the forest quite different to how it had felt at dawn, anticipating cold showers, ‘clean’ clothes, and tasty food.