Gulls and Speckled Green Eggs

Several types of dummy eggs were used to know behaviour and preferences of herring gulls about size and colour.

The picture shows the influence of egg size and colour on retrieval.
The numbers indicate the relative sizes of the dummy eggs used in tests.
Thus herrings gulls:
- prefer the larger of two eggs of the same colour
- prefer the speckled egg over an unspeckled egg of the same colour
- prefer green eggs over brown egg
Curiously, the gulls prefer a green background colour to the normal speckled brown colour of gull eggs, even if inferior size. For example, a size 5 green egg is more attractive than a size 6 natural coloured egg. Because they also prefer eggs with speckles, this leads to the surprising observation that a size 5 green speckled egg is more attractive than a size 8 natural coloured egg.

Ethological Experiments - From University of Plymouth, Department of Psychology.