Tropical rainforests, the facts

Tropical rainforest diversity

Although tropical rainforests cover only 6 – 7 % of the land on earth, they are host to more than half of the terrestrial species known on our planet.  No less than 70 % of all known vascular plant species are found in the tropical regions! The tropical rainforests host far more than half of all mammal and bird species known to science and every year new species are still being described.  The outrageous numbers are reflected in the weirdest forms of adaptations of species: lots of the smallest, biggest, most colourful or strangely-shaped species from specific genera are found in the tropical rainforests. The keys to this diversity success are the following facts:

  • Tropical forests are found on the equator and were much less affected by the big climate changes in the past. While during the ice-ages most of the species in other regions were eradicated or struggling to survive in small areas, species of the tropics could quietly  continue their evolutionary processes and highly specialised life-forms still originated.
  • Food supply is generally year-round available. There are no explicit dry seasons in the tropics and annual rainfall is very high. These conditions lead to the evergreen forests  as a climax vegetation, where there are year-round fruiting and flowering trees.
  • The humid conditions and hot temperature are ideal for rapid growth and decay, and causes a very high biomass production. These conditions lead to the very complex structure of a tropical rainforest with 4 strata: the forest floor, the understory, the canopy and an emergent tree layer.  Due to the rapid growth, decay and very humid conditions, micro-ecosystems are developed in every layer. You can often find on a branch in the canopy a moss and herbal layer and even small saplings growing on these branches. The complex and rich forest structure finally means, more ecological niches and more space for co-existing different species.

Tropical bird diversity

More than 5000 bird species are found in the tropics and no less than 31 bird families are endemic to the tropical rainforests. 38 bird families are dominant families. Typical examples of the endemic families, which means that all their members only occur in the tropical rainforests, are Toucans, Woodcreepers, Cotingas, Leafbirds, Cassowaries and Birds of Paradise. Dominant families are Pigeons, Parrots, Hummingbirds, Kingfishers and Hornbills, which are often numerous and have their biggest species diversity in the rainforests.

Again the rainforests are home to the most bizarre an striking forms in bird community. Species such as the diminutive Pygmy Parrots or chicken sized Crowned Pigeons for New Guinea,  Cock of the Rock, Picathartes, Nocturnal Curassow and Palawan Peacock Pheasant are just a handful of examples.

Now I am getting a little subjective, but plenty of the world’s best birds live in the rainforests: Resplendent Quetzal, King bird of paradise, Banded Pitta, Northern Cassowary, Helmet Vanga, Horned Guan, Philippine Eagle, Numfor Paradise Kingfisher, Pompadour Cotinga, just to name a few, they don’t live in the desert, do they? 

The rainforest birding experience, part 1:

birding under tough conditions - chasing the pitta

As a birder, sofar there is no reason not to visit the rainforests, but now it comes to a little persistence to reach the birders climax. Here’s an impression of what you will have to go trough.

The rainforest is plenty of birds, but you don’t see them. At least not immediately. The best birds, you have to hear them first. But they don’t sing all day, let alone all year. They sing by preference when you are still tired and just recovering from a poor night’s rest. 

Classic birder’s faith: get up at first light and listen for the birds. The best rainforests are often in remote places, so you will not be able to get breakfast before you start birding. You will have to walk an hour in the dark to reach the good forest just before sunrise. You will get hungry by the time you will come close to see a target-species.

Best period to hear the rainforest birds singing is just at the beginning of the rainy season. Theoretically there are no rainy seasons in tropical rainforests, they are characterised by a constant very high annual rainfall. Reality is that there are two seasons: a very wet one and an extremely wet one. It’s at the start of the second one that most of the interesting birds are becoming vocally active. But back to the subject, you’ve started your early morning trip, it’s already quite hot and you find yourself on the trail in the primary forest, but apparently you are not alone: around sunrise there seem to be billions of cicadas around, producing each hundreds of decibels. I suspect their only goal is to be the first one to make your eardrums explode.

Luckily sometimes the cicadas stop their chainsaw-imitations, just to give you the slight impression you might have a chance of coming close to see your wanted bird. During this silence you might hear him, you might not.

When you hear the bird and you want to localize it’s silent ventriloquial call, it is nearly impossible because: the cicadas bursted out in noise again and you can’t hear the bird anymore. Or because the bird has stopped singing after it started pouring rain, it’s the start of the ‘extremely wet season’ after all. Or simply because one of the characteristics of a ventriloquial call is that the sound seems to come from everywhere and searching for it will lead you nowhere.

But you are very lucky today, the bird keeps whistling a soft huuuuu and after a few minutes, you’ve managed to point out more or less the direction. The bird is hidden off-trail , just behind a small but steep slippery hill. The bird won’t come closer and you will have to climb it, but not before crossing a knee-deep muddy gully, where probably one of your boots will get stuck. Of course the hill is full of tangled and vicious spiny vines, in which your clothes will get stuck or worse, your arm will be thorn. You’ve lost some precious time, it’s starts to become even hotter, which might mean the bird will soon stop being vocal and will start foraging in another place, sweat is pouring down your skin, from both the heath and the increasing stress of possibly missing the precious bird.

You are a tough birder and you keep going on. After  you’ve crossed the gully and the hill, the bird is still singing and seems close enough now to start searching for it. Right from the moment you’ve stopped to walk and you want to look for the bird, your  glasses will start to get blur because of your sweat condensing. Don’t worry, if you don’t wear glasses, your binoculars will get steamy. The only thing to do is keep calm, clean quickly but gently your glasses or bins, or in my case clean them both. Do this without any abrupt movements, the bird is probably very close now, you just don’t see him, or if you wear glasses you just don’t see anything. After the cleaning, scan quickly the environment, first bare-eye, later with bins.

Your strong smell and sweat starts to attract loads of mosquitos, who seem to have a particular interest in your facial orifices. If they don’t buzz in your ears or nose they will harass your eyes for a while, before landing on an itchy place such as your nostrils. Just don’t pay any attention to them, any movement might scare the bird now! The bird is still singing at regular intervals and close by. If you first thoroughly scan the forest floor because the bird is known as a ground dweller, this bird will exceptionally be singing form a perch hidden  in the lower canopy. After losing ten minutes and giving the surrounding leeches, enough time to slowly climb your limbs, you will realize the bird is just ten metres away from you in a small but dense sapling. An explosion of scarlet and purple combined with subtle bright blue markings on a black background reveals itself now as a Black-headed Pitta!  Imagine the joy of finally finding such a delicately coloured creature in such a hostile environment and you will come close to understand the joy of birding in a tropical rainforest.

But congratulations, mission accomplished. Enjoy the bird for a few tens of seconds, he will then soon hop to the ground and quickly disappear in the open understory, but not before nicely picking up some leech from the ground. Have a nice day mister Pitta! Time to remove the three leeches, who by then had reached your belly and will unfortunately leave a red bloodspot on your only left clean shirt. Plenty of time now to hit away every mosquito within reach of your arm and start to think about walking back for breakfast.

This is what more or less happened to me and my wife in Danum Valley while chasing a Black-headed Pitta. A few minutes later when reaching the trail again, we bumped into a group of American birdwatchers, who were obviously shocked by our bewildered appearance: we were full of dirt, scars and I stood there grinning with a red stain on my shirt. After listening to our experience and hearing we went off-trail, they concluded: those Belgians, they don’t care about their health! But we couldn’t care less, we had seen our pitta!

The rainforest birding experience, part 2:

moments of easy birding - mixed species flocks

Luckily, birding is not always that tough in the tropics. Quite the opposite is the experience one goes through when observing a huge mixed species flock. My own most mindblowing experience ever took place in Manu,  a national park with the size of Switzerland and home to 10 % of all bird species of the world. The day when I had arrived at Cock of the Rock Lodge, a ‘friaje’ had started. This is the Spanish word for a sudden strong temperature drop to about 10 degrees Celsius. Moreover it was raining all the time and the entire landscape was covered in thick fog. At the same time all bird activity seemed to have dropped down, and apart from the amazing cock of the rocks who were still displaying and some birds coming to the feeders, I didn’t almost see any bird.

The next day, same scenario and I also  saw ‘confused and apparently disorientated birds’ form either the lowlands or higher altitudes. Great was my surprise to find a group of ‘frozen’ hoatzins along a tiny forest stream at 1500 metres of altitude! But I hadn’t come to the mountains to see again lowland birds...

The third morning I woke up, there was still no evolution in the weather and I was getting pretty frustrated: I was in the most species-rich environment in the world, had  only seen very few birds, and still had an amazing number of target birds to go for. Three hours later, sun started to pierce through the clouds and it quickly warmed up. Within five minutes I found myself in the middle of an incredibly huge mixed species flock, filling all the forest strata and moving on at a slow speed. This spectacle lasted for almost half an hour. I saw about a several hundreds if no a thousand of birds passing by and I was able to determine more than 45 species! And what species: the bulk consisted of strikingly coloured Tanagers and some Mountain tanagers, and they were accompanied be no less spectacular individuals such as a Highland Motmot, a Crested Quetzal, a Crimson-mantled Woodpecker and a Cock of the Rock. Some smaller Antbird species, Hummingbirds, Woodcreepers and Tyrant Flycatchers were nervously foraging  as if they all wanted to catch up with their lost time the previous days! As if this wasn’t enough a Tiny Hawk, a rarely encountered species, showed up and started chasing the tanagers. What a morning reward that was! This just to illustrate that the birding in the tropics is often unpredictable but hasn’t always to be tough.

The rainforest experience, part 3: use all your senses

All the previous descriptions deal mainly with what you see, but for understanding the complete rainforest experience you need two extra senses.

Imagine getting up at first light and walking through the wet vegetation at Danum Valley, in Borneo. The moist humus and the plenty of decaying material all spread a strong  but pleasant and typical forest smell. Early morning at the begin of the breeding season is always a guarantee for an amazing choir. You’ll hear beautiful whistles produced by Babblers, simple songs produced by Wren-babblers, monotone repetitive calls from Barbets, weird mechanical or staccato calls produced by Broadbills or forest Kingfishers and simple notes from a handful of Bulbul species. If you are lucky the king of the Southeast Asian songbirds, the Straw-headed Bulbul, will be present. From time to time you will hear the wingbeats of huge Hornbills flying over and the more subtle ticking or clicking calls from tiny frogs. Less subtle are the sudden bursts of cicadas trying to overrule every other sound, but don’t worry they will stop as suddenly as they started. Imagine then the subtle start of a duetting pair of Bornean Gibbons giving first soft and later loud, clear and outdrawn melancholic crying and bubbling calls to each other. I still have to encounter the first person who doesn’t get chicken skin from a moment like this!

But enough reading, just listen to some samples of the amazing rainforest sounds by clicking on the links under here.

Cicada 1, Borneo

Cicada 2, Borneo

Cicada 3, Mount Kinabalu - Borneo

Red Howler Monkey, Amazone

Siamang, Malaysia and Sumatra

Straw-headed Bulbul, Malaysia, Borneo and Sumatra

Musician wren, Amazone

Helmeted Hornbill, Malaysia, Borneo and Sumatra

Black-and-Yellow Broadbill, Malaysia, Borneo and Sumatra

Pale-vented Bush-hen, New Guinea and Northern Australia

Brown Oriole, New Guinea

Common Potoo, South and Central America

Capuchinbird, Amazone

Buff-spotted Flufftail, Africa

Great Blue Turaco, tropical Africa