studied one of Darwin's Finches*, (medium ground finch) in Galapagos Islands*   (UGalapagos)  

  medium ground finch lives on seeds, cracks them open via force of its beak
  the Grant's studied finches on Daphne Major, a small island (800 sq. yd) north of Santa Cruz.

   in 1977 the island had only 2mm of rain instead of its normal 130mm...
          drought (also in 2003) resulted in a loss of 84% of medium ground finch population
          most died of starvation,
                  primary food source, seeds of Tribulus cistoides --> were now hard to open   
                  unless birds had large, deep beaks, [... the survivors had deeper beaks]

    Natural Selection adaptation to changed environmental conditions for 1 trait (beak depth)
                  lead to 4% increase in average beak depth of survivors (graph of 1976-1978 data*)
                  Offspring of survivors in subsequent years had beaks 0.5mm deeper.
                  This type of evolutionary change is known as character displacement.
   
  back                                  HHMI video on finch speciation^{15 min View@home}