Tag Archives: birds

From Neotropics to Afrotropics: Rainforest birds and ecological niches

Guest writer: Luke L. Powell

Sunrise over rainforest canopy in the Brazilian Amazon.
Sunrise over rainforest canopy in the Brazilian Amazon.

Back in the fall of 2012, I was wrapping up my last of four field seasons in the Central Amazon – Manaus, Brazil. My study site, the Biological Dynamics of Forest Fragments Project, was set up for its remoteness: “MOTFA” is what we replied when asked where we worked: Middle Of The F&%*ing Amazon.

forest canopy
One of our more simple field camps near Manaus, Brazil – pretty basic living.

I spent the early part of my career very much focused on those rainforest birds of the Central Amazon – the antbirds and ovenbirds and woodcreepers and all the rest. I had previously worked in Costa Rica as well as Peru, so in Manaus I had some idea of what I was getting myself into bird-wise. In other words, within the Neotropics (tropics of the Americas), the families, and often the genera of birds that frequent rainforests are pretty consistent. Despite the diversity of Manaus, my experiences elsewhere in the Neotropics had prepared me somewhat for what to expect from the birds – which bird families were where, which would be sensitive to rainforest degradation, and which families and genera held which niches.

Fast forward a couple of years and my research has moved from the new to the old world tropics. When starting this transition, I was curious to see if the patterns that I understood from the Neotropics would hold in the Afrotropics – Equatorial Guinea in particular. Why Equatorial Guinea you say?! Well, this Massachusetts-sized country nestled squarely in western central Africa has the full complement of African rainforest fauna: elephants, chimps, gorillas and a dizzying array of colorful birds. But the wildlife is under intense threat from development: Equatorial Guinea discovered oil in the 1990’s and has since been pumping oil, laying down asphalt and putting up buildings as quickly as they can. Several parks were also set aside, but it’s not clear what the sensitive bird species even are or how good of a job those parks actually do at protecting those sensitive species. To fill the gaps of knowledge in this rapidly-developing country, colleagues and I started the Equatorial Guinea Bird Initiative – an NGO dedicated to exploration, education and ecology in the country. We’ve since expanded to mammals as well and changed the name to Biodiversity Initiative.

When I set off for my new project in Equatorial Guinea, the birds were entirely different and I pretty much had to start from scratch on understanding the community. You see, the African and South American continents split off such a long time ago that the bird communities have diverged to a tremendous agree, so much so that most of the families in the Neotropics don’t even exist in the Afrotropics. Fortunately for me, in most cases, there are very close yet unrelated analogs holding the same ecological niches—the role that an animal plays in the rainforest community.

The first place I looked was to the canopy—for an analog of those loud, colorful, Neotropical fruit-eaters with enormous bills: toucans. And immediately I was satisfied in finding that hornbills – the ecological equivalent of toucans – are both abundant and species rich in Equatorial Guinea. This represented a beautiful example of convergent evolution: when two unrelated species converge to fill a similar niche and body plan; dolphins and sharks are a classic example. Unfortunately, because of their large body size, the largest hornbills are often shot by hunters seeking bushmeat. As Africa continues to develop, fewer and fewer of these charismatic hornbills will remain.

forest canopy
Me holding an African Pied Hornbill (Tockus fasciatus) in Oyala, Equatorial Guinea

Next I looked to the understory, where in the Neotropics, ovenbirds and antthrushes accounted for much of the diversity. In the Afrotropics this primarily niche is filled by an unrelated family: the (Old World) thrushes (Turdidae). The American Robin (in the US) and European Robin are well known members of this family. These birds are stocky with a prominent chest, and strong legs and feet built for hopping and walking along on the forest floor – just like their Neotropical counterparts.

Forest Robin (Stiphrornis erythrothorax) captured and banded in Equatorial Guinea
Forest Robin (Stiphrornis erythrothorax) captured and banded in Equatorial
Guinea

But what about mixed species flocks? In the Neotropics, these multi-species groups of insectivorous species are dominated by the antbirds (Thamnophilidae) with Thamnomanes antshrikes leading the charge with their whip-crack calls. African mixed species flocks are dominated by the greenbuls (Pycnonotidae), a cryptic group of often greenish-colored birds that are ubiquotous in the mid story. Though far less is known about these Afrotropical assemblages of mixed-species flocks, in the Eastern Arc Mountains of Tanzania, The Square-tailed Drongo (Dicrurus ludwigii) has recently been found to be the flock leader. Although not a greenbul, this drongo (family Dicruridae) does make a whip-crack rallying call like its Neotropical flock-leading counterpart.

Forest canopy
Flock-leading Dusky-throated Antshrike (Thamnomanes ardesiacus) banded near Manaus, Brazil.

And what about the Neotropical warblers (Parulidae) – those nimble insect-gleaning gems? In Afrotropical rainforests, these are matched by the Old World Warblers (Sylvidae), a drabber but ecologically equivalent family that are also common tropical-temperate migrants – with many of these breeding in Europe. And the ultra-diverse aerially acrobatic Neotropical Flycatchers (Tyranidae)?

In the Afrotropics these find an ecological equivalent in the Old World Flycatchers (Musicapidae), like the oft-studied Pied Flycatcher
In the Afrotropics these find an ecological equivalent in the Old World Flycatchers (Musicapidae), like the oft-studied Pied Flycatcher

If you’ve spent enough time in Neotropical forests (or you had a great guide on your bird tour), you’ve eventually stumbled on the Old Man of the Forest – the trogon. Most are in the genus Trogon and all are frugivorous and strikingly bright, beautiful canopy birds. Much to my delight, I found that this family exists in the Afrotropics and is no less spectacular. Equatorial Guinea has two species in the genus Apaloderma, one of which was caught by my field crew just last week. I’ve since learned that the Asian tropics (my next frontier?) have a few species of trogons as well – most in the genus Harpactes.

forest canopy
Ornithologist in training Amancio Motive Etingüe holds a Bar-tailed Trogon (Apoloderma vitattum) near his home town at Ureka, Bioko Island, Equatorial Guinea

And last but certainly not least, my favorite Neotropical bird family (or subfamily, depending on your taxonomy) is the curiously-moving woodcreepers (Dendrocolaptidae). These ovenbird relatives have modified claws and stiffened tails that they use to hitch themselves vertically up trunks and branches gleaning insects from the bark as they go – not unlike creepers and nuthatches of temperate forests. In Manaus there are 13 species of woodcreeper, each of which has its own unique and curious niche. Strangely enough, this group seems to have no ecological equivalents in Afrotropical rainforests! There certainly a few woodpecker species in Equatorial Guinea, but none are particularly common aside from perhaps the Buff-spotted Woodpecker (Campethera nivosa). Why this niche is essentially empty is a mystery to me, but it sure seems there’s a big haul of Afrotropical insects on tree trunks that are not well exploited.

forest canopy
The Duke of Woodcreepers: Red-billed Woodcreeper (Hylexetastes perrotii) captured near Manaus, Brazil. Note the unusual green skin on the feet and around the eye.

So I’ve found that there are tons of cool birds in the Afrotropics – most with ecological niches similar to that of an analogous family in the Neotropics, and at least one group (the woodcreepers) without. What is a clear difference between Neotropical and Afrotropical communities is how much more poorly the Afrotropical species are understood. With development booming in Africa and human population on the continent projected to quadruple by 2100 – much faster than any other continent – there is a great need to understand and protect these African birds. For me, Equatorial Guinea is a microcosm of the situation in the rest of Africa, which is one of the reasons I am now focused there. What are the keystone species such as flock leaders (drongos?) and seed dispersers (hornbills)? Which species and ecological groups are most vulnerable to disturbance such as logging and agriculture (terrestrial insectivores? large, hunted species?). How many cryptic species exist – those that look alike but are unique species only differentiable by song? Are the birds of isolated islands such as Bioko, Equatorial Guinea, subspecies, or are they actually full (and endemic) species worthy of protection as such? With more work, we can understand the ecology, evolutionary history and habitat requirements of many of these poorly known Afrotropical gems, which will help us to protect them in this time of intense change in Sub-saharan Africa.

forest canopy
A sacred Bubi forest in Equatorial Guinea, Africa.

Treeboat in a Ceiba: When Dreams Go Wild

treeboat, rainforest, forest canopy, Dominican Republic
Treeboat is the penthouse of the tropical rainforest, and this is the view.

 

treeboat, rainforest, forest canopy, Dominican Republic
The branches holding the treeboat are an epiphyte, a strangler fig growing out of the top of the ceiba. That’s right. One of the largest trees I could see around me was sticking out of the top of another tree.

 

treeboat, rainforest, forest canopy, Dominican Republic
The rigging setup keeps the climber in the tree, even while sleeping.

Suspended on taught 1-inch straps, a treeboat is much more than a mere “hammock”: it is an out of body experience. Lie on a treeboat in the forest canopy and you float amongst the branches and birds. There is no sensation of gravity, or ground, or down, only of out, up, and air. You are weightless, and in a treeboat high in the canopy it is easy to feel as though you are in a dream.

I have been dreaming for 20 years of sleeping in the largest tropical tree I could find. Sometimes dreams are meant to come true, and sometimes they are not. Other times the dream takes on a life of its own. This is one of those stories.

The largest tree in the New World Tropics? Look up to the ceiba (Ceiba pendantra) and ask no more. Ceibas are so enormous that the Maya Indians believed them the pathway that souls take to reach heaven. Only a fool would dare to climb where angles tread, so call me a fool.

treeboat, rainforest, forest canopy, Dominican Republic
Climbing a ceiba is like climbing in a tropical garden in the sky.

 

treeboat, rainforest, forest canopy, Dominican Republic
Nearly every surface was draped in epiphytes of every variety. Here is a tank bromeliad.

This fool’s journey takes place in the Dominican Republic. Deep into Los Haitises National Park, next to a muddy watering hole called Poso Ventura, rises a ceiba that all the locals in the little town of Los Limones know. Even before I climbed the tree I was somehow famous, everyone on the street asking if I was really planning on sleeping in the giant tree. Geez, no pressure, folks.

And so it began. Two hours of hiking across the rolling limestone trails, sweat dripping from my chin in the near total humidity.   One hour to shoot ropes over limbs and climb past a vertical cascade of leaves, vines, and roots shooting out of the tree’s trunk. Another hour scrambling up and down limbs, hanging the treeboat in five different positions until one finally worked. By that time I was so filthy that my own smell was, honestly, revolting. I dined on crackers, sardines, and peanuts, enough to leave me positively starving after a day of so much work. I was rationing my water too, and the lack of real food and enough water left me dizzy. Not the best frame of mind when you are 120 feet off the ground. When dusk turned to night the mosquito swarm went rabid and with no place to go the hour of truth finally arrived. I climbed in, more than ready to rest and hoping for the treeboat to take me away to dreamland.   One thing you need to know, friends: treeboat don’t disappoint.

What a trip! It’s hard to know where “up” is when the frogs are chirping, croaking, and burping from 20 feet above your head, outward in every direction, and down 120 feet. Bats would burst into my airspace on fluttery wings, crackling over my stomach, then swooping under my back. I heard a buzz and gazed out into blackness to see pairs of tiny green headlights swerving on unseen roads until one landed on my arm and I ID’d the driver as a 2-inch beetle. After too many hours in socks, my naked toes throbbed with every heartbeat, providing the rhythm for it all. And the insects? Godalmighty – how could I hear anything over the whining cicadas and all their chorus?

treeboat, rainforest, forest canopy, Dominican Republic
The ceiba was filled with anoles, hunting, displaying, sunning, and mating.
treeboat, rainforest, forest canopy, Dominican Republic
The blurred wings in the center mark an Antillean Mango (a type of hummingbird – Anthracothorax dominicus), feeding on nectaries at about 110 feet high.
treeboat, rainforest, forest canopy, Dominican Republic
The view from my room.

All in all it was way too weird. If sleeping in a “normal” forest is an out of body experience, then sleeping in a tropical ceiba took me out of my mind. Did I sleep? In fits. The mosquitoes, held at bay by an improvised netting, shreaked for blood only a finger length from my face and did a decent job of keeping me unnerved. I remember a moment when I felt like rolling over and, unaware of my surroundings, stuck my left leg out into space. I put it right back in bed and clinched tight, determined to stay in the treeboat and live a little while longer. After nearly 11 hours of mind tripping, the dawn chorus of vireos and bananaquits announced it was time for a bathroom break. That’s right. Insufficient food and water combined with a lot of nerves is a good recipe for some “movement” and desperate measures demand desperate means. The ferns will thank me. When Chivero arrived to walk me back to Los Limones, and after a breakfast of sardines and crackers for my parched tongue, I packed my bags and rappelled down the rope to plant my feet once again in the land of sane and normal folk.

treeboat, rainforest, forest canopy, Dominican Republic
Gut check: was it good for you? Yeah, baby!

Would I do it again? Tomorrow!!

And you should too.  But first some advice. The best way to install a treeboat in a ceiba is to stand on the shoulders of giants. Thomas Hayes got me to, and into, the ceiba. Will Koomjian and Jamz Luce taught me the basics of rope wrenching and treeboating. Amanda Sills sewed the rain canopy and mosquito netting for my treeboat. Treeboats were invented and are sold by the good folks at New Tribe – required gear for tree nuts of all ages.

treeboat, rainforest, forest canopy, Dominican Republic
Thomas Hayes checking it all out. Thanks to Thomas for being a good friend.
treeboat, rainforest, forest canopy, Dominican Republic
Chivero poses at the base of the ceiba. The buttress roots alone are four times his girth.

Bald Eagles at home

I’m biased. I love Bald Eagles. There are those who will say they are just lazy eaters of carrion, glorified vultures as it were. I think they’re awesome. The white head and tail are brilliant against the brown back and wings. And lazy? I once saw a male Bald Eagle spot an anchovy floating half a mile away on the Pacific Ocean. In one long swoop, without a single wing beat, he dropped from his cliff perch, glided low over the water, and clutched that anchovy with a massive craggy foot. It was an in-your-face demo of grace and power, a display of total confidence. When I saw that I jumped up whooping and hollering.

When was the last time you got to observe Bald Eagles at the nest? If you’re not a biologist, the answer might be “never.” Unless you have friends in the right places. Early this year Bob Christensen, president of the group Friends of Deer Flat National Wildlife Refuge, asked Canopy Watch to install nest cameras at Deer Flat. He had two nests that were out of sight and whose annual fates were a mystery. Happy to oblige, Bob. Who would have guessed that simple trail cameras would take such great photos! I won’t kill the buzz of these great pics with a lot of talk. Enjoy.

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What an incredible image! One eagle, probably the male, delivering nest material in his talons.
What an incredible image! One eagle, probably the male, delivering nest material in his talons.
Can you believe this?!  One eagle perched, one flying, and three eggs in the nest.  Incredible view of eagles at home.
Can you believe this?! One eagle perched, one flying, and three eggs in the nest. Incredible view of eagles at home.

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Canopy Watch International
The eggs never hatched. By 19 May there was only one left in the nest.

All photos © Friends of Deer Flat National Wildlife Refuge, and USFWS.

A research trip on Northern Goshawks

I’d like to introduce you to the Northern Goshawk (Accipter gentilis).  This predatory bird rules the forest.  They are battleship gray with eyes that reflect the blood color of squirrel and bird meat that they eat and feed their nestlings.  Goshawks are as fearless as they are fierce.  If you get anywhere near the nest they will come at you with talons open, and you have to dodge and duck or risk getting your face raked open.  To learn more about Goshawk research in Idaho, visit the blog of Rob Miller.

Northern Goshawk, Intermountain Bird Observatory
Meet the Northern Goshawk, absolute ruler of the forest. Photo © Robert Miller.

As a biologist and tree climber, I am asked on occasion by other biologists to aid in their research.  Such is the case here, where I helped Intermountain Bird Observatory and Boise State University with research on one of the coolest raptors in North America.  It’s no lie that I admire this bird.  I weigh about 65 times more than one of these birds, but it takes a lot of nerve to climb into one of their nests because they are literally trying to rip my head off, and they have the means.  But I digress.  The few photos below tell the story of a climb into a single nest in June of 2015.

On the ground looking up a lodgepole pine (Pinus contorta) that makes up this stand.
On the ground looking up a lodgepole pine (Pinus contorta) that holds a Goshawk nest near the top.

Goshawks like to nest in mature forests with trees of different ages and sizes.  On the Sawtooth National forest that means quaking aspen and lodgepole pine.  The above tree was about two feet in diameter, and the nest was about 40 feet high.

Halfway up the tree, the view looks like this.
Halfway up the tree, the view looks like this.

Lodgepole pines aren’t usually very big, and it only takes a few, maybe 30 minutes, to get up the tree.

Getting close to the nest, and this is the first good view.  The trick is to climb high enough past the sticks and branches to be able to reach into the nest.
Getting close to the nest, and this is the first good view. The trick is to climb high enough past the sticks and branches to be able to reach into the nest.
Reaching for a Goshawk chick in the nest.  They don't like it much!  There are two more in the background, standing as far away from me as they can get.
Reaching for a Goshawk chick in the nest. They don’t like it much! There are two more in the background, standing as far away from me as they can get.

Once at the nest, the trick is trying to get my hands on a feisty bundle of feathers that wants nothing to do with the clumsy white monkey with a helmet.  They have talons and sharp beaks but don’t really know how to use them yet.  Still, it’s important to be cautious and not hurt the little guys.

There is a Goshawk chick in my right hand, and you can see the banding crew in the background.  In a few more seconds I'll lower it to the ground in a soft cotton sack attached to the climbing rope.
There is a Goshawk chick in my right hand, and you can see the banding crew in the background. In a few more seconds I’ll lower it to the ground in a soft cotton sack attached to the climbing rope.

The next task is to get squirming and angry birds to the ground.  I slide them into an elastic sleeve, slip them into a soft cotton bag, and lower them to the ground where a team of biologists is prepared to attach leg bands and take blood samples.

I'm about to return this Goshawk chick to its nest.  All that remains is to slide it out of the sleeve and lay it in the nest.
I’m about to return this Goshawk chick to its nest. All that remains is to slide it out of the sleeve and lay it in the nest.

I lower the chicks one by one, and after they are “processed” (fancy biologist word for getting banded and any needed samples taken, weighed, etc.) I raise them on the rope one by one.  Above, one chick is in the nest, and I’m about to slide another out of its sleeve and back into its home.

Northern Goshawk chick displays its new color band.  Apparently it likes the color purple.
Northern Goshawk chick displays its new color band. Apparently it likes the color purple.

This chick has realized that we mean no harm and are dishing out free jewelry, so it has calmed down a lot.  OK, just kidding.  But you can see some features of the nest in this photo: loose sticks, and lots of greenery that adults use to “decorate” (another biologist term, as if raptors really decorate their homes) the nest.  It is speculated that the fresh pine branches help repel flies that are attracted to rotting squirrels and woodpeckers in the nest.  Hint: doesn’t work!

Rappelling from the tree on a figure-8 is quick and easy.
Rappelling from the tree on a figure-8 is quick and easy.

Biologists don’t take this kind of work lightly.  We know that our intrusion has an impact on the birds.  Our goal is to be in and out of the nest in less than an hour.  Having good climbing skills and being a trained ornithologist help to reduce the time.  But honestly?  It’s a lot of fun.

As always, if you like this post please share or subscribe to the blog!

All photos © David L. Anderson, except the fine Goshawk photo at the lead, compliments of Rob Miller.

Seed dispersal in an empty forest

Scientific thinking works like this:  First, we make observations about the natural world.  Next, based on those observations we can make inferences, or hypotheses, that are possible explanations for our observations.  Finally, we can predict what will happen if we somehow alter the set of circumstances upon which our observations and hypotheses are based.  The last step is to conduct tests to see if the hypotheses and predictions are true.  This is how scientists go about learning how the natural world works.

Let’s do this with seed dispersal and see what we can learn.  Based on previous blogs, let’s start with the observations.

OBSERVATION #1:  Plants don’t fly.

Um, yeah.  I’m a reasonable guy, and I can buy that one.  Because plants don’t fly, some species in the rainforest use sheer trickery to get animals to eat their fruits and disperse the seeds all over the land where they will grow into new plants.  Think of this as survival of the fittest, plant style.  Doesn’t sound familiar?  Read some earlier blogs.

OBSERVATION #2:  The forest needs animals.

Um, wait a minute.  Isn’t it the other way around?  Without a forest the animals don’t have a place to live, therefore animals need the forest.  Right?  Perhaps, but the opposite is also true.  What we learned in two earlier blogs is that without animals like toucans to disperse seeds, many forest plants, from lofty trees to pesky mistletoes, don’t stand a chance of ever spreading their genes into a next generation.  So yes, the forest needs animals, as in winged and legged dispersers of seeds.

OK, because plants don’t fly, the forest needs animals.  Now the scientist in me asks, “What will happen to the rainforest if the animals were to disappear?”  Maybe the seed dispersers go on strike or something.  For a scientist with too much time on his hands it is simply too much drama.  Even better, it’s the subject of today’s blog, and we will give our drama a name, “Seed dispersal in an empty forest.”  I bet you can’t wait!

But first, let’s take a trip to the rainforest and meet the cast.

White-faced monkey, Cebus capuchinus, seed disperser
White-faced monkey (Cebus capuchinus). Monkeys are major dispersers of large seeds. Monkeys love to eat fruits, they clamber all around the forest canopy, and they are messy eaters who drop stuff they don’t want, like seeds. Photo © Roy Toft.
Central American agouti, Dasyprocta punctata.
Central American agouti (Dasyprocta punctata). Agoutis are rodents in the tropical forest that eat seeds, unlike other animals that are after the fruit. They carry seeds in their mouths, some get dropped here and there, and one day a lucky seed carried away by an agouti will grow into a nice sapling and later a large tree. Photo © Roy Toft.
Toco Toucan, Ramphastos toco, seed disperser
Toco Toucan (Ramphastos toco). Toucans have large bills for a reason. They use them to reach out and pluck fruits from trees. But they don’t poop the seeds out; after flying through the forest they cough them up. Many seeds actually require this type of treatment. They are evolved not to germinate unless exposed to the acid in animal stomachs. Photo © Roy Toft.

Now let’s skip ahead and visit some predictions about the empty forest.

PREDICTION #1:  If we lose our seed dispersers from a particular forest, there will be a decline in plant species with large seeds that rely on animals to “fly” their seeds for them.   Makes total sense.  Without seed dispersal those large seeds will fall under the parent tree where most will rot in piles, and the few survivors will choke each other out in a battle for sunlight.

PREDICTION #2:  In the empty forest, there will be fewer sapling trees, period.  This one is more complicated, so let’s think about it.  Seeds that are transported away from the parent tree are more likely to live, and most of those that fall under the parent will perish.  Without animal dispersers to help out, few seeds in this forest ever get to travel to safe sites, and fewer ever germinate and grow into trees.  So, overall we predict fewer total saplings than in a nearby forest with all its animal dispersers still in place.

Now for the weird part – I’m not making this stuff up!  This little drama has actually happened in real life and scientists are watching the whole thing.

Screeeech! – Rewind!  The forest lost its animals?!?  Yes.  In developing countries in the tropics like Brazil, Colombia, and Peru, food is hard to come by.  When a new road punches through the rainforest for logging, mining or oil exploration, humans move in, and hungry humans fan out with rifles and eat the fauna.  Agoutis, toucans, monkeys – that’s what is on the menu.  Given enough time, a small community of people can totally eradicate the larger wildlife species in the forest.

And come to find out, when animals disappear from the forest, the whole forest gets turned on its head.  I didn’t have to make up today’s predictions; I borrowed them from Dr. John Terborgh at Duke University.  Terborgh and his team counted animal seed dispersers and saplings in two forests in Peru.  The forests are only 90 km apart and the only difference is that in one the large wildlife that disperse seeds are basically extinct due to hunting, and in the other no hunting takes place.

The predictions turned out to be true.  There are fewer saplings in the empty forest, and of those saplings the scientists found, almost none grew from large seeds dispersed by animals.

This is bad news for biodiversity.  The preservation of biodiversity depends on natural balance.  Once we lose the trees with large fruits that animals eat, this forest will never again be home for toucans and monkeys.  Next we lose the animals that eat animals, like jaguars and eagles.  A rainforest without wildlife just isn’t a rainforest anymore.  It’s quiet, lonely, and just plain unnatural.  Biodiversity goes in the tank.

Animals need forests.  Forests need animals.  And so do we.

jaguar, Panthera onca
Jaguar (Panthera onca), largest cats of the Americas. Photo © Roy Toft.
Harpy Eagle, Harpia harpyja, The Peregrine Fund
Harpy Eagle (Harpia harpyja), largest eagle in the world. At the top of the food chain, they depend on the animals that eat seeds too. Photo © José de Jesús Vargas Gonzales of The Peregrine Fund.

Photo Credits

CWI thanks Roy Toft of Roy Toft Photography and Photo Safaris for another fine set of professional photos.

References – for more information.

Terborgh, J., G. Nuñez-Iturri, N. C. A. Pitman, F. H. C. Valverde, P. Alvarez, V. Swamy, E. G. Pringle, and C. E. T. Paine.  2008.  Tree recruitment in an empty forest.  Ecology 89(6): 1757-1768.  pdf

Seed dispersal in the rainforest canopy: mistletoe and the Lovely Cotinga

One of the tallest trees in the Neotropical rainforest, the mighty nutmeg, depends on toucans and rodents to disperse its seeds to places where they can grow. Here is a tree that can reach 150+ feet (45+ meters) in height, and without the help of rainbow-colored birds and bucktoothed mammals its seeds are doomed. What happens to small plants that grow in the forest canopy 100+ feet off the ground and don’t even have roots in the soil? Do they also need wildlife to disperse their seeds?

Mistletoe is great example of a plant that grows high up in the forest canopy and never touches the ground. Never touches the ground?? How does a plant do that? Epiphytes are those plants that grow on the surface of other plants. In a shady forest all the plants are competing for light. Some plants like the nutmeg tree win this little battle by growing head and shoulders above the rest. Other, smaller plants win by groing on the branches of trees, high up in canopy where they get all the sunlight they need. Orchids. Bromeliads. Cacti. These are just some examples of plants that bask in the sunlight on the branches of trees high in the rainforest. They get sun from above, water from the rain, and when leaves decompose around the roots that they grow along the surface of branches, they get their food. But what do these plants do with their seeds? And how did that puny plant get way up in the tree anyways? For a mistletoe, and lots of other plants, the answer is birds again.

Here is one of my favorite birds of the Neotropical rainforest, the Lovely Cotinga. This bird oozes cool! It’s a day-glow, neon turquoise blue with a plum purple throat. I bet astronauts can see these dudes from space.  And yes, the actual name of the bird is “Lovely Cotinga.”

A male Lovely Cotinga perches like a jewel atop the rainforest. Photo © James Adams of the Lodge at Pico Bonito.
A male Lovely Cotinga (Cotinga amabilis) perches like a jewel atop the rainforest. Photo © James Adams of The Lodge at Pico Bonito.

 

And here is the object of cotinga desire, Psittacanthus rhyncanthus, a species of mistletoe. There is nothing a cotinga loves more than to chow down on mistletoe fruits.

 

Mistletoe berries (purple fruits lower left) are the gas that light up a male Cotinga like this one. Photo © James Adams of the Lodge at Pico Bonito.
Mistletoe berries (purple fruits lower left) are the “juice” that light up a male Cotinga like this one. Photo © James Adams of The Lodge at Pico Bonito.

And herein lies our rainforest intrigue. The mistletoe, like the nutmeg, is a trickster. It puts out hundreds of small fruits that birds like the Lovely Cotinga love to eat, but this time the joke is on the birds. After a cotinga or other unsuspecting bird goes in for a tasty meal of fruits it finds out that its gullet is full of seeds, seeds that are so sticky, so gooey, it’s like having a mouthful of glue globs. To rid itself of these seeds the cotinga has to literally wipe its face across the surface of a tree branch until the seed sticks to the branch. Voila! Just like that a mistletoe is born. From branch, to bird, to branch, the mistletoe never leaves the forest canopy and is transplanted by an agent in electrified blue feathers. Stranger than fiction? That’s life in the rainforest.

Don’t believe it? You can see for yourself at places like The Lodge at Pico Bonito, Honduras, where Lovely Cotingas show up by the flockful every year during the rainy season from January to March. James Adams, a manager at the Lodge, witnessed an interesting dispute over some mistletoe between two cotingas.

An adult and a juvenile male Lovely Cotinga dispute a favorite perch. The tree branches are being killed by mistletoe plants spread by the contingas themselves. Photo © James Adams at the Lodge at Pico Bonito.
An adult and a juvenile male Lovely Cotinga dispute a favorite perch. The tree branches are being killed by mistletoe plants spread by the contingas themselves. Photo © James Adams at The Lodge at Pico Bonito.

James tells us: “Evidenced by the numbers of mistletoe stuck to this branch [note the little green leaves under the branch – that’s them], Cotingas have favored perches. And apparently they don’t like to share with just anyone. When this young male (note the maturing purple and blue plumage) flew in and tried to accompany this bright blue male, the older male would have none of it. And so a war of silent beak gaping ensued, with both parties opening and closing their beaks at one another, until the younger bird flew off.”

In other words, it appears from watching these colorful birds that they need the mistletoe just as much as it needs them.

Parting shot: Gotta love these guys, right?

Lovely Cotinga (Cotinga amabilis) in Pico Bonito National Park, Honduras. Photo © Roy Toft
Lovely Cotinga (Cotinga amabilis) in Pico Bonito National Park, Honduras. Photo © Roy Toft