Beak Heat: Evolutionary Theory of Bird Bills May Need Revision

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A finch’s beak evolves according to the size and shape of available seeds. That conventional wisdom is one of the most accepted facts in science—it has been proved again and again in research that began in the Galápagos Islands, and stretches from Charles Darwin in the 1830s through to the modern work of evolutionary biologists Peter and Rosemary Grant. Case closed—right? 


Not necessarily. Two new studies, led by Smithsonian Conservation Biology Institute ornithologist Russell Greenberg, strengthen a budding theory that beak size may also be an adaptation to regulate temperature and conserve water. “Very few people ever stop to think that maybe these birds actually need water,” Greenberg points out.

Years ago Greenberg noticed that sparrows who live in freshwater-stressed salt marshes tend to have larger bills than their relatives who live just a few kilometers inland. Then, in 2009, he read that thermal imaging revealed that toco toucans lose as much as 60 percent of their body heat through their bills. That got him thinking that maybe birds evolve larger or smaller beaks based on their need to either shed or conserve heat.

Matthew Symonds, an ecologist at Deakin University in Australia, was one of the first to investigate the relationship between beak size and latitude (a proxy for climate). “One of the arguments that was being thrown at us,” Symonds says, was that toucans have exceptionally large beaks, so the “radiator” phenomenon probably would not apply to most birds.

Written By: Sarah Fecht
continue to source article at scientificamerican.com

14 COMMENTS

  1. “That got him thinking that maybe birds evolve larger or smaller beaks based on their need to either shed or conserve heat.”
    Which got me thinking, maybe bird beaks evolved larger or smaller based on their ability to either shed or conserve heat and not for the express purpose to do the conserving or shedding. Just a thought. The other way sounds a bit too intentional and creationistic.

  2. ….strengthen a budding theory that beak size may also be an adaptation to regulate temperature and conserve water. 
    [Emphasis mine]

    I wonder whether this ‘may also’ is the heart of the difference between a change that is just a context specific advantage and an “adaptation” which is something that gives both an advantage and flexibility.

    Very possibly I have completely misunderstand – I do that a lot when talking evolutionary theory. Sigh.

  3. Not in this context, Neo. Any organism can be said to “need” to stay alive and well, after all. The “need” for a particular way of doing that is the problematic, Lamarckian sense, not this one.

  4.  Corylus, adaptations do not have to confer flexibility as well as immediate advantage. If they do happen to, then all well and good, but an adaptation can just as well be in the form of a specialisation as in the form of a general adaptation. It’s all circumstantial. The bird’s beak just turns out to be more of an advantage than was previously realised, because of the “second string” to its “bow”, so to speak. Having said that, most major traits are complex ones.

  5. “Any organism can be said to “need” to stay alive and well”

    I don’t know if I agree.

    If shedding heat improves genetic success, it will continue to improve genetic success until it has no effect or has a negative effect. It is not a requirement, just a reality.

  6. Aquilacane, I suggest you read my earlier post more carefully, because you were replying to something I didn’t say.
    EDIT: To help you, I might point out that Neodarwinian had changed the subject from birds’ beaks to Lamarkism and “need”. I was addressing that issue, not beaks or birds.

  7. Thank you David and Alan.

    I sensed I might be getting it ‘arse-uppeds” as it were!  I like it when people help me to get things correct rather than carry on being wrong.

    I think I had a problem with language there.  “Adaptation” implied “adaptability” in my brain, but – no – they need not be linked in this, or any, instance.

    Although I do wonder whether being able (or just more likely) to develop mutations could be something that is both adaptive and an adaptation?

  8. I know what you mean, Corylus, but “adaptation” is defined in evolutionary biology as a trait that improves “fitness”, not adaptability in the sense you mean. But, as I said before, some adaptations are, indeed, more adaptable than others.

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