Friday- Feathers or Figures? Feathers.

The colony of chestnut-headed oropendolas looked like this right before I left- only 7 days after the birds arrived and started building.

The chestnut-headed oropendola colony looked like this 7 days after the birds arrived and started building- three complete nests and three more under construction. Barro Colorado Island, Panama. Pencil on 8 1/2″ x 11″ Robert Bateman sketchbook.

In a recent post about chestnut-headed oropendolas, I promised to get back to you with better (published) information, and after some searching found The Nesting Habits of Wagler’s Oropendola (Zarhynchus wagleri) On Barro Colorado Island, from the Bulletin of the American Museum of Natural History (1928, Vol. LVIII). Ornithologist Frank M. Chapman sat in a camp chair on BCI and watched a colony at work in a sandbox tree (Hura crepitans). He wrote with great charm about, among other things, the male oropendola’s unusual song:

The courtship, or”crash”call, which I consider the male’s real song, begins with the one just described and adds a sputtering crackle ending in an explosive crash. In my notes I have also termed this remarkable production a sputtering, masticatory, ejaculation.

…and what the bird has to go through to produce it:

It can, indeed, be seen coming as the bird’s body begins to swell from below upward and, rising on tip-toe, he delivers his vocal appeal, then sinks back deflated.

This video I took of the BCI colony shows some of what the male’s display looks like. But really, you just want to see his pretty blue eyes.

It's sort of mysterious how they lengthen their nests- when it's done, this thing will be over two feet long- because the bottom of the basket is sealed over pretty early in the process. But from what I can tell, the bottom weave is kept loose while the female is working down inside, pushing her feet, wings and body against the fibers, adding material and shoving some some more. I think she pushes the nest downward to create a big long stocking. Sketched through a scope, pencil on 8 1/2" x 11".

It’s sort of mysterious how they lengthen their nests- when it’s done, it will measure over two feet. The bottom is shut off early in the process but from what I can tell, it’s a loose, stretchy weave. As she works from inside she presses her feet, wings and body against the fibers, adds more material and shoves again. Sketched through a scope, pencil on 8 1/2″ x 11″.

Chapman’s paper is full of natural history observation and whimsical asides you rarely see in science papers, written in a narrative form about one colony, and no graphs to slow down the storyline. But that’s not all.

Growing oropendola nest, not finished but getting there. The female at right is working on what she hoped would become a nest, but never got that far. This is the "helper" bird that kept interfering and fighting with the female who wove the beautiful nest at left. Chapman observed similar competitive behavior between females, and noted that some took "helper" roles that really hindered. My guess is that this is a young, inexperienced female working on her first nest, and hasn't gotten the hang of it, even after carefully watching (and bugging the hell out of) the successful nest-builder right next to her. Drawn through the scope, 8 1/2" x 11" pencil.

Oropendola nest, not finished, but getting there. The female at right is working on a nest, too, but never got that far. She’s the “helper” who kept interfering and fighting with the weaver of the long nest at left. Chapman saw competitive behavior between females, and noted that some helpers really hindered. My guess is she’s a young, inexperienced female on her first nest who hasn’t gotten the hang of nest-weaving, even after watching (and bugging the hell out of) the female next door. Drawn through the scope, 8 1/2″ x 11″ pencil.

Chapman watched his oropendola colony on Barro Colorado Island, where its long nests hung from a tree beside the laboratory building (now the visitor center). Where did I sketch my oropendola colony? Same spot.

Frank Chapman, watching the oropendolas of BCI. Yup, same birds, different generation. Photo from My Tropical Air Castle by Frank Chapman.

Frank Chapman, watching the oropendolas of Barro Colorado Island. Same birds, same place, different century. Photo from My Tropical Air Castle by Frank Chapman, 1929, D. Appleton and Company.

Of all the chestnut-headed oropendola colonies in the world, I had to go and sketch Frank’s.

Happy Friday.

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About zeladoniac

Debby Kaspari travels the world with sketchbook and binoculars, drawing and painting in wild and not-so-wild landscapes. Norman, Oklahoma is her home base, and she lives there with her tropical ecologist husband and a mackerel tabby named Gizmo.
This entry was posted in Adventure!, Art, bird art, birding, birds, digiscoping, Drawing, Environment, field sketching, natural history, Nature, Panama, rainforest, Science, Sketching, Stupid Critter Tricks, travel, tropics, Video clips, Wildlife and tagged , , , , , , , , , , . Bookmark the permalink.

4 Responses to Friday- Feathers or Figures? Feathers.

  1. Corienne says:

    Wonderrful! Again!

  2. laura33 says:

    What a great post–I love your sketches: the way you show the light on the nest is beautiful, as are the birds (which I want to draw/paint/learn more of myself). It’s really wonderful that you’re in the same spot Chapman was … and thanks for the introduction to his work.

  3. Timothy Ryan says:

    Hey! Where is my Friday fix? It’s that time again!

  4. zeladoniac says:

    Okay, okay! I’m typing as fast as I can:-)

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