Hosts of avian brood parasites have evolved egg signatures with elevated information content
Proceedings of the Royal Society of London. Series B
Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
Reason for embargo
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.
Pomona College–Downing College Student Exchange Scholarship
Royal Society Dorothy Hodgkin Fellowship
DST-NRF Centre of Excellence at the Percy FitzPatrick Institute
Copyright © 2015 The Royal Society
Electronic supplementary material is available at http://dx.doi.org/10.1098/rspb.2015.0598 or via http://rspb.royalsocietypublishing.org.
This is the author’s accepted version. Please cite the published article: Caves EM, Stevens M,Iversen ES, Spottiswoode CN. 2015 Hosts of avian brood parasites have evolved egg signatures with elevated information content. Proc. R. Soc. B 282: 20150598. http://dx.doi.org/10.1098/rspb.2015.0598 available at http://rspb.royalsocietypublishing.org/content/282/1810/20150598.
July 2015, Vol. 282, Iss.1810