The solar owl:  it squawks , it talks, It  flashes its eyes and wiggles its head from side to side. More importantly, as tests in Kona showed, it brings in pueo native Hawaiian owls that will seek and destroy any mice and baby chickens around at dusk.  During the day it scares a number of other birds away from fruit trees.  We planted 1 inch PVC pipe in the ground and the owls sit over the pipe.