New paper on visual complexity & mimicry

Jul 13, 2022

Prinia and cuckoo finch egg

Our paper “Visual complexity of egg patterns predicts egg rejection according to Weber’s Law” has just been published in the journal Proceedings of the Royal Society B. This research was led by Tanmay Dixit, and carried out together with Andrei Apostol, Kuan-Chi Chen, Tony Fulford, Chris Town and Claire Spottiswoode, in a collaboration between biologists and computer scientists. We used machine learning to compute a biologically-relevant measure of egg pattern complexity, and combined this with field experiments in Zambia to investigate how complexity evolves in an arms race between host egg signatures (by tawny-flanked prinias) and parasitic egg forgeries (by cuckoo finches).

Specifically, we quantified the complexity of egg patterns of tawny-flanked prinias (hosts of cuckoo finches) using a machine learning algorithm that optimised the complexity measure such that complexity differences between eggs best predicted egg rejection, according to field data. This means that complexity was quantified in a biologically-relevant manner, and such an algorithm could be used to quantify complexity in other systems.

We also showed that complexity predicts rejection according to Weber’s Law (c.f. our earlier paper on Weber’s Law and how to test it, https://onlinelibrary.wiley.com/doi/full/10.1111/evo.14290; also see the news post at https://www.africancuckoos.com/2021/07/new-paper-published-on-webers-law-and-mimicry). Finally we showed that cuckoo finch eggs have simpler patterns than prinia eggs (see image, with a prinia egg on the left and cuckoo finch egg on the right), suggesting that high complexity in egg patterns has evolved to make forgery of these ‘signatures’ difficult.

 

News

New paper on imperfect egg mimicry

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. Together we combined mathematical tools and field experiments in Zambia to quantify a key difference – “squiggle” markings – between the eggs of hosts (tawny-flanked prinias) and parasites (cuckoo finches). We showed that suboptimal behaviour on the part of prinias allows cuckoo finches to get by with an imperfect copy of prinia eggs.

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New paper on host aggression and hawk mimicry

Our paper “Aggressive hosts are undeterred by a cuckoo’s hawk mimicry, but probably make good foster parents” has just been published in the journal Proceedings of the Royal Society B. In the paper, we investigate the costs and benefits to the African cuckoo of specializing on a highly aggressive host species, the fork-tailed drongo.

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African Cuckoos Team at the Pan-African Ornithological Congress

The African Cuckoos Team had a fantastic time at the Pan-African Ornithological Congress (PAOC15), this year held in Vic Falls, Zimbabwe. Dr Chima Nwaogu gave a plenary talk on “Differing Priorities in the Timing of Annual Life History Events”, while Professor Claire Spottiswoode and Silky Hamama presented during a roundtable session on communities in conservation and research. Silky also presented a poster, with Claire, Jess Lund, Mairenn Attwood and Cameron Blair each giving research talks as well. 

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