New paper on imperfect egg mimicry

Feb 15, 2023

Prinia and cuckoo finch egg


Our paper “Combined measures of mimetic fidelity explain imperfect mimicry in a brood parasite-host system” has just been published in the journal Biology Letters. This study was led by Tanmay Dixit, and carried out together with Gary Choi, Salem al-Mosleh, Jess Lund, Jolyon Troscianko, Collins Moya, L Mahadevan, and Claire Spottiswoode, as part of a collaboration between our group and Prof. Mahadevan and his lab at Harvard University.

Cuckoo finch (parasite) eggs mimic those of tawny-flanked prinias (their hosts), making it hard for prinias to identify and remove these imposters from their nests. However, the mimicry is strikingly imperfect (see image, with a prinia egg on the left and cuckoo finch egg on the right). Why do cuckoo finches lack the “scribbles” of pigment always present on prinia eggs? 

Using both mathematical tools and field experiments in Zambia, we showed that although scribbles are a key difference between these species’ eggs, prinias don’t use the absence of scribbles in identifying cuckoo finch eggs.

These findings explains why cuckoo finches do not mimic the scribbles of prinias – they don’t need to, because prinias don’t pay attention to this aspect of egg patterning. In general, we must test how animals themselves perceive their world, to understand why – to human eyes – such imperfection persists.


Open access link:



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