Nectandra Cloud forest

Brrrrr…. It’s 52 °F in our cloud forest this morning. Not cold by northern-latitudes standard, but downright frigid for the tropics, especially for the two dozen species of Nectandra hummingbirds (of some 50 in Costa Rica).

Imagine the challenge in thermoregulation for an average size (4 in) hummingbird such as the Rufous-tailed hummer pictured below with a body weighing as little as a single grape (0.18 oz).

As most birds, it must maintain body temperatures between 100-108 °F to stay active.  For these birds, foraging for food means to be able to keep heartbeats around 1200 beats/min to sustain wingbeats of 50-70/sec to fly at average speed of 34 mph.  This flight ability allows the hummingbirds to hover about the flowers for nectar during feeding, and even to fly backward — unique acrobatic locomotion among avifauna.  (Human: 60-100 heartbeats/min and jogging speed of 4-6 mph )

Anatomically, the hummingbirds have the largest relative heart to body size.  The rufous-tailed’s heart constitutes 2.4% of its body weight (compared to ~0.5% of average human ).  Its need for oxygen during flight translates into higher red blood cell density of 6.59 million/ml (~5 million/ml for humans).

To stay fit, hummingbirds must eat and drink a lot  — more than half its body weight each day in nectar and twice in water, the equivalent of some 1000 flowers/day (favorite examples among many blossoms at Nectandra in photos below).  

Critical protein, fat and mineral supplements come from small insects, fruit flies, spiders, larvae, insect eggs, etc. (examples on Sobralia orchid, photo top right).  These food items are extra-critical during egg laying and feeding of average clutch of two young birds (when the mother birds themselves do not eat).

In addition to the extra caloric need during motherhood, some hummers must store fat (about 0.1 oz), enough for 24-26 hr of long flights (longer than the 22 hr limit for Boeing 777 non-refueling flight).   For example, the Ruby-Throated hummingbirds migrate across the 500 miles Gulf of Mexico.  They can clock at 25 mph or 650 miles maximum, enough to cross the Gulf of Mexico non-stop with energy to spare.  Rufous hummingbirds can migrate 1865 miles (with stops) between Mexico and Alaska/Canada.

The high metabolic rate creates interesting physiologic challenges. For one, the high caloric intake must be metabolized, channeled and expended fast enough not to overheat. As result, the hummingbirds have vastly efficient sugar digestion, increased tissue gas transport and matched respiration rate. To give an idea of what it takes to achieve the same high level of metabolism, an average human would have to consume 100 lb. of pure glucose per day.  The corresponding human metabolism, however, would generate lethal body temperature equivalent to ~752 °F .

The tiny-bodied hummingbirds must work at marginal and exquisitely tuned energy balance.  For example, to counteract the risk of overheating, hummingbirds do not have down feathers, even for those in the temperate-zone during winters. Instead, they rather conserve energy over long period, as during sleep, by going into a short hibernation state known as torpor — a lowering of body temperature to a steady minimum of around 60-70 °F, dropping 60-90% of its metabolic rate and >30% water loss in this torpor state. 

Hummingbirds, in sum, are superbirds. Their rapidly adjusting metabolic rates, the highest of any animals, allow them to withstand great ambient temperature swings. They may be the smallest but have the largest heart, the greatest appetite and the sweetest tongues.  They can fly the fastest and longest, besting the newest and longest range jet plane without refueling.  They can hover and fly backward like no other, birds or machines.

Most of all, hummingbirds are undeniably among the most beautiful of birds with their flashy, iridescent plumage.  Their feathers are wonders to behold — a topic worthy of another conversation.  Please join me on a eye opening chin-to-tail hummingbird feather inspection in the next blog.

By recent estimate, there are at least 500,000 fauna species in Costa Rica, of which 493,000 are invertebrates (insects, spiders, molluscs, crustaceans, crabs).  By comparison the entire US has fewer than one third the number of invertebrate species but 300X the land size of tiny Costa Rica — an effective difference of 1000 fold.

Most visitors to Nectandra Reserve have heard about the extraordinarily high biodiversity of the wet montane cloud forest.   On arrival, they expect to see a tropical jungle, teeming with animals and hopping with insects, in full view as in a zoo without cages.  Yet, all they see is the lush, thick, tangled, green vegetation behind the mist. They see few things with legs or wings, certainly not in a number or density that would impress. 

Puzzled, my visitors would politely ask “Do you have any animals?” As their guide for the day, I never get tired of seeing their eyes gradually widen in the course of our interpretive hike as they slowly realize the beauty of nature’s astounding subtlety.  It isn’t the quantity or furriness, but the compelling impact of the sightings that will convince them there is more to it than meets the eyes. By the time they leave, most visitors can grasp the phenomenal biodiversity with minimal help from me. Yes, the animals are here, thousands of them.  Many are in plain view, but only if our mind is prepared for the encounter.  One such example is captured in the photo below of a small fallen branch on the ground.

With so many animal species living in the same space, they become interdependent in a most efficient but cruel way possible.  Every species is food for other species.  To survive, every prey’s overpowering instinct is to hide, physically or visually, or both.  One most obvious way to conceal is to stay in the dark, and out of sight.  This is true for the smallest to the largest, from gnats to jaguar.  That explains why the majority of the invertebrates, reptiles, amphibians and mammals are nocturnal.   For many of the diurnal organisms, invisibility through camouflage — the ability to blend in the surroundings — is vital to survival. 

Let’s go back to the photo above. Look again with these three clues: 1) It’s in the left half of the photo, 2)  It’s in a patch of leafy plant,  3)  It’s green with 6 legs and two long antennae.  Still not visible?  If not, inspect the blow-up below of the same photo.  A katydid (Haemodiasma spp) is now revealed, perfectly camouflaged in the patch of liverwort, a cousin of the mosses. The next photo is an even closer shot of the head.

Not to be outdone, other members of this Tettigoniidae family (katydids, grasshoppers and crickets) are equally remarkable in the myriad of ways they can blend into their environment.  Take this close up photo of a dry leaf for example.  Note the pigmentation, the areas of discoloration, the flecks of tissue damage and randomly attached green vegetation. How faithfully would you guess a katydid can imitate this leaf ?

The answer is — absolutely perfectly — because the above “dried leaf” is actually a cropped view of the leaf katydid below.

Here is another example of the high art of concealment of another species of katydid. The green leaf katydid on the left is almost perfectly matched to the begonia leaf on the right.

The fierce competition for food sources in the wild tropics means every organic and proteinaceous scrap is consumed almost instantly.  Nothing is left to waste. Carcasses are rare finds.   The next photo is of such a rare item — a pair of wings from a dismembered katydid. 

At first glance, when found on the ground, they were indistinguishable from the other dried leaves nearby.  On inspection, however, that they were of two perfectly mirrored “leaves”, including discoloration and holes, left no doubt they were not of natural leaves.  The symmetry was too perfect, the ribbing and veining (see photo below), even down to every blemish.  Had we found only one wing, only a biochemical or DNA test could confirm its insect origin.

As perfect as the cryptic coloration of the katydids (at least to the human eyes), one false move is all it takes to become someone’s meal. Witness, in the photo below, the unfortunate katydid that came too close to the spider web of the orb weaver Eriophora fuliginea. In spite of the size difference, the larger katydid was no match for the stickiness and strength of multi-stranded spider silk. It was all over for the katydid within mere seconds.

Concealment as a defense tactic comes in as many forms as there are organisms. Nature is an infinitely large repository of supremely clever solutions for as many problems. It behooves us humans to learn from them.

Please join us at Serendips.net next month for more adventures and examples.

I am inaugurating this blog series with a virtual visit to Nectandra Cloud Forest, to set the stage for an introduction to an ecosystem that’s is rapidly shrinking. Thirty years ago, when the scientists first described what is a cloud forest, they estimated around 11% of the world tropical rain forests to be cloud forests — forests that are immersed in cloud most of the year. Today, it is estimated that only 1.5% is left and disappearing. At today’s rate of climate change, most of it will be gone before we know it.  Rather than lament its impending loss, I would like to use the time and opportunity to celebrate this Garden of Eden and to share with you our experiences, the highlights and the sense of wonderment living in such an environment.

Imagine yourself dangling from a parachute, floating straight down on Nectandra forest looking down through your feet at 150 m (500ft) in the air.

You are about to land on what appears to be an immense head of broccoli where each tree constitutes a floret. But unlike the florets, the trees in the canopy are not clones. No two look alike because they are likely to be of different species. They come in all shades of green, each with a different texture and coarseness.

In the image above, the tightly packed tree canopy shows hardly any gaps between trees and even less between foliage. Tree branches are not visible.  In fact, the degree of gaps in the forest can be taken as an inverse measure of the density of the forest.  The denser the trees, the less gap areas in the canopy. Scientific computer software can count the black or gap pixels per unit screen area as a way to measure and monitor forest growth in drone images .

Drop down another 50 m and look ahead to get a different view. 

The trees appear now more varying in shapes, in heights and no longer pure green.  Under the oblique light, some of the trees definitely take on a brownish hue.  Leaves changing color? Dying trees? Look closer and you will note that the brownish green is not foliage, but thick mats of plants on the branches and trunks of trees.  The brownish growth are hundreds of intergrowing species of the liverworts and mosses — the tiny iconic plants of the cloud forest known collectively as the bryophytes.

A startling different view emerges as you descend to about 15m from the ground. You are now just below the upper canopy, looking through the tangles of the branches.  The presence of the bryophytes is overwhelming.

The accumulating bryophytes and plant detritus provide the necessary nutrients and loamy support for other epiphytic flora (plants that grow on other plants). Add the steady, constant misting during the day all year to the mix, plants with aerial roots can now grow and thrive.  Well known examples are the bromeliads (air plants), orchids, ferns, lianas, even begonias, to name just a few. Shown in the photo immediately below are impressive inflorescence of hanging orchids Oncidium sp. (see inset) on the left and an endemic Columnea macrophylla on the right (in the same family as african violets). Visitors on the ground are likely to miss this floral hanging garden because of the altitude.

From this height another striking, eye-catching group of cloud forest iconic trees are the tree ferns. The dozen species of tree ferns at Nectandra are beauties to behold, with their majestically large fronds (~1.5m) and great stature (up to 10-15 m).

Let’s drop down to the forest floor. Now look up. The view is typically through thick foliage of understory plants, and through epiphytes-laden branches. From this vantage point, nearly every surface is layered with bryophytes and epiphytes.

Look down, more bryophytes, on tree trunks, branches, leaves, rocks and soil…

Zoom in on the tree trunks, now the moss (below left) can be distinguished from the intermingling liverworts on the right, two representatives species among hundreds on the reserve.

We have come to the end of our vertical tour. On your future visits, I hope to introduce you to many more forest features and riveting fellow residents. Please check in for our next blog for more unconventional virtual tours of the Nectandra Cloud Forest.

to experience Serendips!

What is a serendip?

…..a chance encounter, an unexpected discovery, a happy accident, a startling fluke, an unforeseen experience, a fortuitous involvement, an unintended contact, a sudden insight, and so many more . . .

Serendips challenge our mind’s readiness for discovery. They often give no warning, and do not advertise. Our ability to detect and experience them rests on our mind’s readiness and alertness.

Just as all irrepressible children with their memorable discoveries, we at Nectandra want to share the excitement of our numerous serendips with the family members, friends and anyone who share our love for Nature and her profoundly beautiful living creations.

Starting this August, we will post any unusual findings and observations on subjects of tropical nature in general, and of cloud forest in specific with readers of our blog serendips.net The articles will be short and entertaining (we hope) and definitely informational.  Please subscribe to register your interest in becoming a Serendipper at Nectandra — the realm of furry plants and mossy animals .