Following Darwin’s Finches in the Galapagos

We were fortunate to receive a grant this year from Earthwatch Institute to return to the Galapagos Islands, and follow up on an intriguing finding from Luis’ dissertation work here: that human settlement on Santa Cruz Island may be influencing the evolution of beak morphology in the medium ground finch, Geospiza fortis.  Specifically, Luis and colleagues found that there was a greater divergence between small and large-beaked morphs of G. fortis at an undisturbed site (El Garraptero) than at a site adjacent to a human settlement (Academy Bay).  They hypothesized that the abundance of novel human food types at Academy Bay (e.g. rice, potato chips, crackers) may be relaxing selection on beak morphology and resulting in a homogenization of this population of G. fortis (View the original article in Evolution here). 

We’re following up on this work by conducting detailed feeding observations of G. fortis in both perturbed and unperturbed sites, as well as continuing our multi-year program of banding and measuring all 3 species of ground finches found in the area:  the small (G. fuliginosa), medium (G. fortis), and large (G. magnirostris) ground finch.

A male G. fortis feeding on a seed of Scutia spicata near the Charles Darwin Research Station, Santa Cruz Island. Photo credit: D. Sharpe

A male G. fortis feeding on chocolate residue from a discarded Milky Way wrapper in the town of Puerto Ayora, Santa Cruz Island. Photo credit: Ken Sparrowhawk