GJ Tattersall, B Arnaout, MRE Symonds (2017) The evolution of the avian bill as a thermoregulatory organ. Biological Reviews 92: 1630-1656
What’s it about?
A review of what we know about how birds use their bills to keep cool and regulate their body temperature. It covers everything you might want to know about bill anatomy, development and physiology in relation to thermoregulation, and then investigates the ecological and evolutionary consequences of these roles – touching on aspects such as Allen’s rule (which explains the tendency for bills to be smaller in colder environments), phenotypic plasticity, and the possible effects of climate change on bird bill evolution.
What’s the story behind it?
Glenn Tattersall, an old friend from PhD days, has been working for many years on all sorts of aspects associated with animal thermoregulation (check out the link to his webpages). Most remarkably he has clearly shown (in toucans, and other less obviously ‘showy’ birds such as song sparrows), that birds use their bills as thermal radiators. Back in 2010 we had a paper that employed a comparative approach showing that one consequence of this thermoregulatory function is that bird species that live in hot climates tend to have evolved larger bills. Late in 2015, Glenn contacted me saying “hey I’m writing a review of bird bills and thermoregulation – would you like to contribute some stuff on Allen’s rule and the link between climate and bill size”. Craftily, he sent through an effectively very complete draft, just with a few choice sections not completed, ready for my input. How could I refuse?