Kingfishers, their beaks, and diving – Physical Modeling and CFD.

New paper out today in Royal Society Interface, that I’m rather excited to be a co-author on.  Led by Dr Kristen Crandell from Bangor University, and with her former undergrad Rowan Howe (I believe it start out as his undergrad project), the paper takes a look at how beak shape across kingfishers correlates with lifestyle.

You see, the thing is (and I did not initially realise this), kingfishers are actually a pretty diverse group.  And they don’t just fish.  There’s 114 species of Kingfisher in the world, and some are entirely terrestrial, some exclusively dive for fish, and some live a mixed life.

What Kristen and Rowan set out to test was how beak shape followed mode of life and phylogeny. The set-up was pretty cool – 3D printed heads of kingfishers, kindly supplied from the laser scans collected by the Mark My Bird project, were dropped into water from a consistent height, and accelerometers recorded how quickly the 3d printed beak and head slowed down when they hit the water.

The 3D models – raw scan data in pink, and cleaned models all scaled to the same beak length in blue.

We then added a simulation aspect, and this was where I came in.  We set-up a similar scenario – 3D kingfisher head in a virtual flume using Autodesk CFD, and then took a look at drag forces generated by three different beak morphologies (from terrestrial, aquatic, and mixed species), as well as the flow patterns around the beak.

Simulations around three kingfishers. The terrestrial species, Dacelo on the right clearly creates a larger bow-wave in front of the beak which would be bad for trying to catch fish.

The physical and computational experiments showed that the diving species of kingfishers had narrower, longer beaks, but also shallower (dorso-ventrally) than their terrestrial counterparts, after phylogeny was accounted for.

You can download the paper here:
https://royalsocietypublishing.org/doi/10.1098/rsif.2019.0125

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