Ask the Experts: Question #2

Welcome to Question #2 of our Ask the Experts feature where each week we pose one of your questions to our three birding experts and then see their responses.

Please welcome this week’s three birding experts:

Pepe Castiblanco: Co-owner and proprietor of Casa Botania B&B and professional birding and nature guide.

David Rodriguez Arias: Tropical Biologist and natural history guide in Monteverde, Costa Rica.

Uzvaldo Franzini: Birding guide and monthly contributor to the prestigious Zanti Journal of Zoological Sciences.

Question #2: (from San Vito Bird Club member David Fielding) ‘The Sunbittern’s wings, when spread, each have a big beautiful eye-like spot. What do you suppose is the evolutionary reason for that spot? Is it to scare away predators? Is it to attract a mate? Are the wings spread to display the spot during courtship? . . . Or is it for both reasons?’

Pepe: This is a question that goes beyond my knowledge and has to be answered based on my observations in the field. Two things trigger the bird to display the ‘sunset’ or evil eyed patterns: gliding and landing and/or deterring others to approach their nesting site by standing between the nest and the intruder and lowering its head and spreading its wings fully. Does it work now? Will it have to adapt through the next thousand years? Very likely yes to both questions. For now, all we can do is enjoy every sighting with respect and keeping our distance discreetly. 

Below, a picture of the wing display when landing on a rock in Turrialba.

(photo by Pepe Castiblanco)

David: That’s an excellent question! As far as I know, the Sunbittern (both male and female) use the spots on their wings to communicate both things. They use the spots to express their interest in each other, or to sound the alarm when there is an intruder in their territory. We can’t forget that those colours look different to them, because the spectrum of colours that birds see is wider. 

And since we’re talking about the Sunbittern, I would like to share something else interesting about its closest relative. The Kagu (Rhynochetos jubatus) is found in New Caledonia, and because of this, it is believed that at one time they shared the same habitat in Gondwana. With Continental Drift, however, the two species were separated. 

I hope one day those readers who haven’t seen the Sunbittern yet have the opportunity to marvel at this stunning species!

Uzvaldo: I am reminded of that great song by Donnie and Marie Osmond; ‘A Little Bit Country-A Little Bit Rock ‘N Roll’.

I love the Sunbittern.  It’s one of those birds existing in its very own private family (Eurypygidae).  The Sunbittern’s appearance gives us ‘a little bit of this and a little bit of that’.  Imagine if evolution tried something new…combining the best parts of a heron with the best parts of a rail.  Then, to top off the experiment, evolution added some spectacular colors and bold eye-spots on the wings.  Are the eye-spots for defensive purposes?  Are the spots there to attract a mate?  Once again we have a situation where we get ‘a little bit of this and a little bit of that’.  Most researches suspect both purposes are in play!  

I can think of another Costa Rican bird that uses the ‘a little bit of this and a little bit of that’ evolutionary strategy; our very own Rufous-tailed Jacamar.  Even though the Jacamar is not closely related to hummingbirds or to kingfishers, it looks a little like both of them.


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