Data from: Behaviorally-induced camouflage: a new mechanism of avian egg protection

When animals potentially occupy diverse microhabitats, how can camouflage
be achieved? Here we combine descriptive and experimental methods to
uncover a novel form of phenotypic plasticity in the camouflage of bird
eggs that may be present in other avian taxa. Soil from the bare substrate
adheres to the blue-footed booby´s (Sula nebouxii) pale eggs, which
parents manipulate both under and on top of their webs. Analysis of
digital images confirmed that dirtiness increases progressively during the
first 16 days of the incubation period, making eggs more similar to the
nest substrate. Observations of 3,668 single-egg clutches showed that
probability of egg loss declines progressively over the same timeframe and
then remains low for the rest of the 41-day incubation period. An
experiment showed that when chicken eggs are soiled and exposed in
artificial booby nests, they are less likely to be taken by Heermann´s
gulls (Larus heermanni) than clean eggs.