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Large finches (large ground finch, Geospiza magnirostris), with large beaks,
are more likely to survive and to reproduce when conditions favor large seeds.
This was shown in a study by Peter and Rosemary Grant: a drought in 1977-1978
left only large seeds in the Galapagos, and larger birds with larger beaks were favored.
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Smaller finches (medium ground finch, G. fortis), which have smaller beaks,
are more likely to survive and reproduce when conditions lead to an excess of small seeded plants,
as occured in 1982 when an El Nino event brought rain and a bumper crop of small seeds.
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