- researchers found no correlation with summer temperatures but a clear one for winter — the coldest winters were associated with the smallest beaks, whereas warmer winters were associated with larger beaks.
Posted: 13 Jul 2017 05:20 AM PDT see full ScienceDaily article here
…in the 1990s, researchers began to explore a new question concerning the relationship between climate and the evolution of beak size…..[before this study]… feeding habits were believed to be the greatest driving force in beak evolution…
…[comparing] differences between individuals of the same species that are living in wildly different conditions…. the researchers found no correlation with summer temperatures but a clear one for winter — the coldest winters were associated with the smallest beaks, whereas warmer winters were associated with larger beaks.
…Allen’s Rule, which states that warm-blooded animals living in cold climates will have shorter limbs and appendages than those that live in warmer climates. The biological mechanism behind this rule is thermoregulation — more body surface area helps animals to shed heat better whereas less surface area helps them to conserve it. Since a bird’s beak plays a large role in thermoregulation — it has lots of blood vessels and is not covered in feathers — researchers wondered whether hotter climates beget larger beaks and colder climates beget smaller ones. Indeed, studies revealed that climate has influenced beak size, but not which type of climate had more of an overall impact….
Nicholas R. Friedman, Lenka Harmáčková, Evan P. Economo, Vladimír Remeš. Smaller beaks for colder winters: Thermoregulation drives beak size evolution in Australasian songbirds. Evolution, 2017; DOI: 10.1111/evo.13274