Page 196 - The Error of the Evolution of Species

The Error of the Evolution
of Species

amounts of rainfall in the hot, rainy season. Moreover, the

atmospheric phenomenon known as El Niño takes place at
irregular intervals every two and 11 years, and at different
levels of intensity, also alters the climatic balances. At such
times there is excessive rainfall; subsequent years are then
generally dry and arid.
The level of rainfall is of vital importance to the ground
finches that feed on seeds. In years of plentiful rain, ground

finches can easily obtain the seeds they need to grow and
breed. In years of drought, however, the plants on the is-
lands may produce a limited and inadequate amount of
seeds, as a result of which some finches starve.
Grant and his colleagues measured the rainfall on
Daphne Major as normal in 1976, but counted only one-fifth
of this amount a year later, in 1977. During the 18 months
of drought from the middle of 1976 to January 1978, there
was a significant drop in the quantity of seeds on the island

and a major reduction in the numbers of ground finches.
The population fell to 15% of the year before. They as-
sumed that most of the other birds had died, and that a few
had migrated.
Grant and his team made another important observation,
noting that the finches that survived the drought were rather
larger than normal and had slightly wider beaks. The aver-

age beak of the ground finches on the island in 1977 was

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