Robert I. Bowman and Anne Carter, "Egg-Pecking Behavior in Galapagos Mockingbirds," The Living Bird, Tenth Annual, 1971

SHELL PATTERNS OF CHICKEN EGGS USED IN PECKING EXPERIMENTS

A, plain white; B, plain white with one red oval mark; C, plain white with black "crack" lines; D, black spots on pale blue ground-color; E, plain chalky blue; and F, plain yellow on blunt half and plain red on pointed half.