Thursday, July 13, 2006
Galapagos Islands Finches Rise to the Challenge
Competition Drives Big Beaks Out of Business
by Elizabeth Pennisi
"When intruders started eating up all the large seeds on one of the Galápagos Islands, the resident finch population retooled, researchers report on page 224 of this issue of Science (14 July 2006). In about a year, their beaks shrank, becoming better equipped to eat smaller seeds.
"At the beginning of the study, the medium ground finch (Geospiza fortis) shared the island only with the cactus finch, which uses its pointed beak to eat cactus fruit and pollen. Lacking competition from other finches, the blunt-beaked medium ground finch depended on smallish seeds, which were easier to eat. That is, until a severe drought in 1977 devastated the plants that produced small seeds. For the most part, only those birds with beaks big enough to break open large, hard-to-crack seeds survived; in just a few generations, there was a 4% increase in average beak size (Science, 26 April 2002, p. 707)." (Read more.)
Photo credit: B. R. GRANT ET AL., SCIENCE