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Is there an important relationship between epiphytic orchids and birds?

April 8, 2011

Yesterday at breakfast I saw a huge Black kite sailing in to Dokmai Garden from the south. When it reached the centre it began circling, using thermic winds to gain altitude. I like this kind of bird watching, a huge bird moving slowly for several minutes, giving me plenty of time to observe characters like the forked tail and white under-wing patches.

I also registered a new bird to Dokmai Garden  in a mango: The Golden-spectacled Warbler. It took me a lot of time to finally observe the characteristic grey cap with two black stripes. This little bird was constantly moving around in the crown, probably catching insects. While observing this new bird species (number 80 in our list), I also observed tailor birds, scaly-breasted munias, oriental magpie-robin and spotted dove.

I looked down at the Vanda liouvillei orchid which grows in the same tree, about one meter up from the ground. It has over 200 flowers, in spite of no nutrient additions. I kept thinking how on earth it gets the nitrogen up there. The bark is fairly smooth, no other epiphytes apart from crustose lichens. The literature usually suggests the epiphytic orchids sustain on degrading cork cells of the bark, but to my knowledge cork or suberin is exceptionally hard to break down and does not contain much of mineral nutrients. The abundance of birds and the flourishing orchid made me come up with the hypothesis that in a healthy forest ecosystem, crowded with birds, there will be plenty of bird droppings to support the orchids’ needs for nitrogen (just imagine a chicken house). Such droppings may burn leaves, but mostly the droppings would hit another branch. Morning dew and rain would dissolve the bird droppings and a diluted nutrient cocktail would coat branches and trunks, where the orchids’ aerial roots can pick up what they need.

Is anyone aware of any ecological study comparing orchid health in a living tree compared with orchid health on orchids growing on bark pieces in an equally shaded area? In a nursery the orchid grower usually sprays NPK 21-21-21 every 2-4 weeks during the growth season, but nobody sprays NPK in the forest. For the Orchid Ark this means we should absolutely focus on keeping orchids in a woodland. Orchid ecology may encompass more essential elements than fungal symbionts for seed germination and pollinators for reproduction.

Please let me know if anyone has read an actual article on this issue.

Eric Danell

For those of you who missed Bauhinia strychnifolia last year, she is in blossom now at Dokmai Garden. A true Lanna endemic!

2 Comments leave one →
  1. April 8, 2011 8:49 AM

    There is more to this story. We know why epiphytic figs grow on high rise buildings as birds poo the seeds on high. But the most prolific little poo-eer I have to deal with on the eleventh floor is that grubby little insectivore, the misnamed house lizard. These animals are surely poo-ing in the trees and on the rocks as well, to the benefit of epiphytic* and epilythic*plants including orchids which grow on trees and stone.
    * Note: my spell checker dislikes these words and suggests epileptic for the latter.

  2. sandriver permalink
    April 9, 2011 7:45 AM

    Platycerium: a bird’s nest fern.

    The best bark imitating medium for growing orchids is Platycerium roots. It keeps some moisture near the roots and is freely draining. My experience is that it also leeches nutrients to the roots and makes orchids thrive without fertilizers.

    Fallen down epiphytic orchids are turned into compost or ashes (after a fire) on the forest floor. The same happens with fallen down epiphytic Platycerium ferns. Some fall down from the weight of the water that they have absorbed. I have found dried out ones with a weight around 40 kg. They have to be cut into pieces on the spot (because of their bulk) before they can be carried away.

    My suggestion is that you use the fallen down Platyceriums to grow the salvaged orchids. Do not forget the permit!
    If you like to grow your own, more info here: Matt Opel’s Home Page

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