Interesting speculations! I suppose this only applies to ground or open nesters in trees as the cavity nesters wouldn't have much if any light reaching the eggs. I would think that any theory would have to include the cavity nesting birds as well, wouldn't it?
Egg coloration of cavity versus non-cavity nesters would be a good test of the two general hypotheses for egg coloration. If the camouflage hypothesis is correct, you would expect cavity nesting species to tend to produce unmarked, conspicuous eggs. As most nest cavities are not totally dark, the "embryo view" hypotheses would predict that cavity nesters produce, speckled eggs at the same rate as non-cavity nesters. Now we need some data on the two groups of nesters and for that I'll have to do some research and get back.
the function of egg colour in birds
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