"Things You Wouldn't Know If We Didn't Blog Intermittently."
Another reason may be that very bright coloration is often a warning to predators that the organism is poisonous. Non-poisonous organisms will sometimes mimic this signal.
They might be blue to camouflage them as the bird floats in the water. I can imagine a bird's foot and everything attached to it might be a tasty morsel for a submerged predator.
...i want to thank you for your work. You have done really very good site. Great work, great site! Thank you! :PThe Blue Footed Boobies do indeed use them for courtship displays. They do a sort of 'march' raising their legs and feet. Then I think the prospecting female(I think) joins in if satisfied by the display. The only reason I remember this, is because they were mentioned a lot on 'Galapagos' by Kurt Vonnegut :)
Ah... The March of the Blue-Footed Boobies. Sounds like a Laurel and Hardy movie.