The past week has been an eventful one for the hypothesis that thermoregulation requirements influence beak morphology, but there is still more work to be done. Peter Grant complimented the studies but wrote in an e-mail that "The hypothesis would be strengthened by a demonstration that fitness (survival) of birds in the wild varies as a result of variation in beak size–related heat dissipation."
Even if the new hypothesis continues to gather support, it does not negate the elegant studies conducted by the Grants or other researchers in the field; diet is clearly a factor that influences beak morphology, Greenberg says. Rather, the new studies emphasize that traits are often the result of compromises between many different factors.
To Thomas Smith, an evolutionary biologist at the University of California, Los Angeles, the growing support for the hypothesis "means we should reexamine a lot of the works we thought were driven by feeding ecology, and think about thermal relationships. I think it would be particularly exciting to look at this in Galápagos."
Greenberg's thoughts are along the same lines. What does he plan to do next? "I'm going to keep working to make the song sparrow the next Galápagos finch," he says.