My understanding is that megapode eggs are not
turned deliberately and, in fact, do not need to be turned at all.
Evolution of the use of external heat sources for incubation must have
included adaptations to egg/embryo physiology. Inadvertent turning may
occur in the course of mound maintenance, but is not only unnecessary but also
potentially damaging as megapode eggs have shells that are considerably thinner
and more fragile than would be expected from comparison with those of other
birds. Presumably eggs laid in burrows where incubation heat is
geothermally derived do not require substrate maintainance. To what
extent are megapodes 'aware' of their eggs, anyway? I would have thought
that (in the case of the mound-builders and maintainers) the males would focus
almost entirely on mound maintenance and be largely oblivious to eggs (as they
are to chicks). Aren't there cases of enthusiastic mound-maintainers
inadvertently kicking out eggs when opening up the mounds?
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