Data from: Hosts of avian brood parasites have evolved egg signatures with elevated information content

Hosts of brood-parasitic birds must distinguish their own eggs from
parasitic mimics, or pay the cost of mistakenly raising a foreign chick.
Egg discrimination is easier when different host females of the same
species each lay visually distinctive eggs (egg ‘signatures’), which helps
to foil mimicry by parasites. Here, we ask whether brood parasitism is
associated with lower levels of correlation between different egg traits
in hosts, making individual host signatures more distinctive and
informative. We used entropy as an index of the potential information
content encoded by nine aspects of colour, pattern and luminance of eggs
of different species in two African bird families (Cisticolidae
parasitized by cuckoo finches Anomalospiza imberbis, and Ploceidae by
diederik cuckoos Chrysococcyx caprius). Parasitized species showed
consistently higher entropy in egg traits than did related, unparasitized
species. Decomposing entropy into two variation components revealed that
this was mainly driven by parasitized species having lower levels of
correlation between different egg traits, rather than higher overall
levels of variation in each individual egg trait. This suggests that
irrespective of the constraints that might operate on individual egg
traits, hosts can further improve their defensive ‘signatures' by
arranging suites of egg traits into unpredictable combinations.