Brewing up a Scented Storm   Leave a comment

Felipe del Bosque Blog Sept 25 2010

Temp High 84°F  Low 73°F          Precipitation 4.00 ins

At the minute we are sitting under tropical storm Matthew.  The eye of the storm is currently passing over Mexico but it is still drawing a lot of rain from the ocean onto the Pacific coast which in Costa Rica has been put on a yellow alert.  So it is pouring and has been all morning.  It is the kind of weather that may have inspired Gene Kelly into a song and dance routine but it doesn’t solicit that same response from much else.

What is it that causes tropical storms to develop?  During the northern summer and into fall, the sun is more or less directly overhead in the region of The Gulf of Mexico and the Caribbean Sea.  The sun causes intense heating of the sea, which does not heat up as quickly as the land, but holds the heat a lot longer.  This heating causes water to be evaporated from the ocean surface and transferred to the atmosphere as water vapor. The evaporation causes the surface of the ocean to cool.  We now have the driving force behind the storm formation.  The hot wet air expands and rises, in doing so it cools causing cloud formation and precipitation as rain.  The precipitation now releases all the latent heat that was carried by the water vapor from the ocean.

The rapidly rising air normally causes thunderclouds to form and the latent heat released is blown away by winds.  But if there is little wind and the heat is trapped, it further expands the air and an intense area of low pressure starts to form.  Winds now swirl in to the low pressure area, a tropical depression has formed.  These winds evaporate more water vapor from the surface of the ocean, which carry more heat and serve to intensify the situation; the depression starts to feed itself.  As the pressure drops and the wind speeds build the depression becomes a tropical storm.  If the storm stays over warm ocean water it will become a hurricane.

These depressions move northwards and as they move over cooler water they lose a lot of their energy, but not before having precipitated much of the water vapor as rain.  The winds at the centre of a category 5 Hurricane can reach over 150 mph.  Thankfully tropical storm Matthew has not as yet reached Hurricane status.  At the moment it is moving North West along the Atlantic coast of Nicaragua and Honduras with sustained wind speeds of 50 mph although it brought a lot of rain to the whole of Central America as I can readily testify.

I think it is going to be another day in the cabin doing bookwork.  It will give me time to write up some more of the chapters to the souvenir guide to Bosque.  I have been stuck on the rocks and soils of the area for some time, so I need to move along.

After lunch there was the opportunity for a brief walk around.  Up in a leafless tree the bedraggled Black Vultures were holding out their wings to dry.  They are never the most elegant looking of birds and right now in the rain they look even less so.  They were joined by a Crested Caracara, also heavily preoccupied with cleaning itself.  Two pairs of Scarlet Macaws in a nearby tree were grooming and necking with one another.

This evening it is still very wet but not raining.  As the sun set, a Grey Necked Wood-rail started its rapid tick-tock, tick-tock call. Later when I went to count the frogs, the lawns were alive with fireflies, little intermittent flashes of silvery light, but tonight coming from whichever direction.  It is like walking through an enchanted landscape.  Way off in the forest I could hear a Crested Owl calling, not the familiar hoot or twit twoo of children’s stories; this is more of a guttural “uk” sound.

Philip is a biologist, writer and photographer as well as the onsite naturalist guide at Bosque del Cabo Rainforest lodge on the Osa Peninsula, Costa Rica.

Photo Feature

One day as I was walking just out of the grounds of Bosque, on the road down to Puerto Jimenez, a metallic green insect flew right in front of my face and landed at eye-level on a leaf beside me.  The insect was a gorgeously colored Orchid Bee, sporting the characteristic rich metallic greens and blues that would outshine any sequin covered red carpet celebrity.  I say it landed but that is probably not quite the correct adjective.  Its motion was halted by the bee grabbing the edge of the leaf with its mandibles, coming to an abrupt stop and now hanging pendulously like some gleaming enameled jewel about 6 inches from my face.  While it was suspended in this fashion, it proceeded to clean its proboscis by drawing it up through its front two pairs of legs.

Orchid Bee

Orchid bees, particularly the males are solitary bees; you won’t find them living in large hive communities like the Honey Bees.  The females make nests from a variety of materials; plants, resin and mud.  Like other bees, the females forage for pollen and nectar to feed their offspring.  The males, as soon as they emerge as adults leave the nest and go off in search of something different.

As their name suggests, male Orchid Bees seek out orchids.  The orchids they are searching for do not produce nectar but that is of no consequence because the bees are after a different prize.  The male Orchid Bees are perfumers; they make perfume and they need some basic ingredients to perfect their recipes, which is what the orchids supply.

The hind legs of the male Orchid Bees are a miniature chemical laboratory modified for producing heavenly scents, each fragrance specific to the species of bee that manufactures it. Different species of orchid produce different volatile compounds and so are visited by small group of bee species specific to that orchid.  It is not just orchids; there are several other families of plant that have species producing bee attractive volatile compounds too.

The bees gather the scents with brushes on the forelegs; they are then transferred by combs on the middle legs to cavities in the hind legs where they are blended into intoxicating scents.  There are no other groups of animals known to indulge in this elaborate form of perfume production.

At certain times of the year, the male bees gather in a swarm all now liberating the perfumes they have produced into the air of the forest understory.  It has to be assumed that this waft of exotic scent attracts in the females, (who do not visit the orchids or produce perfume), but this behavioral response as yet remains to be proven.

So what are the orchids doing, what do they get out of this, nothing in life is free?  When the male bees visit to collect their perfume producing ingredients, the single anther of the orchid, which is hidden under a cap, is caused by the weight of the bee to drop down and deposit upon it a sac containing the pollen, the pollinarium.  As each orchid only attracts a small number of specific bee species, that then almost guarantees the bee is going to visit an orchid of the same species where the pollen will be transferred and successful cross pollination will have been achieved.

Text and Photographs are taken from the forthcoming book:

The Natural History of Bosque del Cabo by Philip Davison

Species List for the Day


Spider Monkey


Red-tailed Squirrel


Red-lored Amazon

Scarlet Macaws

Grey-necked Wood-rail

Crested Owl

Bright-rumped Atilla

Long-billed Hermit

Chestnut-backed Antbirds

Black-hooded Antshrike

Chestnut-mandibled Toucan


Green Honeycreeper

Bay-headed Tanager

Crested Caracara

Black Vulture


Marine Toad

Red-eyed Green Treefrog

Banana Frog

Olive Treefrog

Tink Frog


Posted September 26, 2010 by felipedelbosque in Philip's Nature Diary

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