Coevolution is the process by which two or more species influence each other’s evolution. Brood-parasitic birds, the cheats of the bird world, give us an ideal opportunity to study coevolution in the wild. Coevolutionary “arms races” arise when hosts evolve defences such as rejecting parasitic eggs, which imposes natural selection for parasitic counter-adaptations such as mimicry of host eggs, and in turn for ever more sophisticated defences from hosts. Three long-term projects in Zambia, the Western Cape of South Africa and Finland, address different aspects of this fascinating model system for coevolution.

Claire Spottiswoode and Gabriel Jamie’s team works on a variety of brood-parasitic systems in Zambia, focusing mainly on three broad questions. First, how do interactions between species generate diversity among individuals? Specifically, how do biological arms races between hosts and parasites shape phenotypic diversity in both parties? For example, parasites diversify to mimic multiple hosts, and in response hosts sometimes diversify with defensive adaptations to foil mimicry, such as visual 'signatures' of identity. Second, how is specialisation to different coevolutionary partners maintained? The genetic basis of signature-forgery arms races is almost entirely unknown. In collaboration with Prof. Michael Sorenson (Boston University), we are using genomic approaches to ask how specialised adaptations to different host species (mimicry of host eggs) are maintained within a single parasitic species (e.g. Cuckoo Finches Anomalospiza imberbis and Greater Honeyguides Indicator indicator) in the absence of parasite speciation. We are also interested in the genetic basis of host defences, and whether convergent genetic mechanisms have evolved in their parasitic mimics. Third, what is the role of phenotypic plasticity (such as developmental differences and learning) in coevolution, and how might such plasticity facilitate exploitation of new host species in the absence of appropriate genetic adaptations? We are addressing this question for indigobirds, whydahs and honeyguides

Fitz Research Associate Jessie Walton has been studying Brown-backed Honeybirds Prodotiscus regulus, which parasitise Karoo Prinias Prinia maculosa at a high rate in the Bot River area of the Western Cape. Brown-backed Honeybirds have blue eggs, highly unusual in piciform birds, broadly mimic the blue eggs of their hosts. Moreover, up to three honeybird chicks are raised in the same host nest, despite killing host young with their bill hooks. How honeybirds escape being killed by their nestmates remains an intriguing mystery.

Robert Thomson’s team works in Finland, where their research focuses on how host pairs of Common Redstarts Phoenicurus phoenicurus can decrease the chance of a Common Cuckoo Cuculus canorus parasitising their nest. Hosts that are able to avoid parasites decrease the fitness costs of parasitism; the earlier that avoidance occurs during the breeding cycle, the lower the cost. Therefore, host adaptations before egg laying should be especially beneficial. The Finnish project investigates the redstart’s frontline defences (nest site choice, habitat selection, nest building decisions) and the cuckoo’s counter-adaptations, including prospecting and laying strategies, which have received little attention to date. Redstarts are the only regular cuckoo host that breed in cavities, which makes it difficult for female cuckoos to lay eggs and for their newly-hatched chicks to evict host eggs/chicks. This project also studies whether cuckoo females use behaviour and physiology to enhance the manipulative signals that cuckoo nestlings use to extract as much care as possible from their foster parents

Activities in 2025
  • We carried out two seasons of fieldwork in Zambia: rainy season fieldwork in January–April on Cuckoo-finches and their hosts (Dr Tanmay Dixit) and dry season fieldwork in September–November (Dr Mairenn Attwood) on African cuckoos Cuculus gularis and their hosts, together with our local field team led by Collins Moya, Silky Hamama and Onest Siakwasia.
  • Mairenn and Claire visited their cuckoo research colleague A/Prof. Rose Thorogood and her team at the University of Helsinki, where they both gave seminars. Claire presented work on the brood-parasitic Greater Honeyguide, while Mairenn presented work on African cuckoos. Both enjoyed a productive and stimulating week learning more about the work of Rose’s ‘Informed Birds’ research team and discussing opportunities for collaboration.
  • Maggie Mwale is continuing with the process of curating the remarkable ornithological collection of Zambian birds made by John Colebrook-Robjent, now housed at Livingstone Museum, supported by the Max Planck–UCT Centre for Behaviour and Coevolution. Maggie is Curator of Ornithology at the Livingstone Museum and has taken a leave of absence from this role to pursue a PhD at the Fitz, which she started in September. Maggie is studying how climate change is altering natural selection on birds’ eggs for camouflage and identity signalling, supervised by Claire Spottiswoode and A/Prof. Susie Cunningham.
  • Joel Radue carried out a successful field season in Zambia for his MSc research on the ecology and evolution of fire dependence in birds, with a special focus on Bronze-winged Coursers Rhinoptilus chalcopterus – one of the focal species at our long-term study site in Zambia. As part of the same project, Joel, together with Jess Lund, Claire Spottiswoode and colleagues Dr Eunbi Kwon and Dr Mihai Valcu from the Max Planck Institute for Biological Intelligence (MPIBI), had a very successful fieldwork trip near Hoedspruit in South Africa in February. They were fitting GPS tags onto Bronze-winged Coursers in order to track their movements in relation to fire. This collaboration is part of the Max Planck–UCT Centre for Behaviour and Coevolution.
  • The birds and fire team (Joel Radue and Claire Spottiswoode from the Fitz; Prof. Bart Kempenaers, Eunbi Kwon and Mihai Valcu from the MPIBI; and Prof. Sally Archibald from Wits University) met near Bremen, Germany, for a very stimulating and enjoyable two-day workshop as part of the collaborative work of the Max Planck–UCT Centre.
  • In November, Maggie Mwale and Claire Spottiswoode both gave presentations at the BOU’s ‘A day at the museum’ conference, at the Natural History Museum in London, on the use of collections in research (Claire in person and Maggie online). Claire introduced the Colebrook-Robjent collection at Livingstone Museum in Zambia and its use in research on brood parasite–host coevolution, and Maggie spoke about her MSc research using the collection, which looked at changes in the eggs of ground-nesting birds in response to climate change.
  • Kyra Stock carried out research into how parent birds ‘know’ what their chicks look like. She did this as part of her master’s research at University of Bonn, Germany, supervised by Dr Wolfgang Forstmeier at the MPIBI in Germany, together with Gabriel Jamie and Claire Spottiswoode and Dr Timo Thünken at Bonn. To conduct this work, she made use of the amazing aviary facilities at the MPIBI and carried out cross-fostering experiments using captive populations of zebra finches. She successfully submitted and defended her thesis in January.
  • Teresa Abaurrea represented the Redstart–Cuckoo research team and gave presentations at both the Oikos Finland conference in Jyväskylä and the Spanish National Conference of Ethology and Evolutionary Ecology in Seville, speaking about how the characteristics of host neighbourhoods affect brood-parasitism decisions of common cuckoos. 
Highlights 
  • Mairenn Attwood graduated with her PhD from the University of Cambridge, with enthusiastic feedback and no corrections from her examiners! Her thesis, focusing on interactions between African cuckoos, their drongo hosts, and the surrounding miombo woodland bird community, was entitled ‘Exploiters and exploited: antagonism, mutualism and mimicry in an ecological community’. She has now joined the Fitz as a postdoc, building on her PhD research with new questions on how mimicry evolves and is both culturally and genetically transmitted. For this, she’ll be comparing different types of vocal and visual mimicry which are either innate or acquired from the environment (starting by focusing on the begging calls of brood-parasitic chicks). She’ll also be diving deeper into sound ecology and interactions between different bird species.
  • Mairenn published part of her PhD as an article in Biological Reviews entitled ‘How do parasites and predators choose their victim? A trade-off between quality and vulnerability across antagonistic interactions’. The article brought together studies on all kinds of antagonists – brood parasites, blood-sucking lice, food-stealing gulls, pathogenic viruses, predators, and even parasitic genetic elements. Across this huge diversity of life, a common theme emerged: antagonists face the same trade-off between choosing victims that are high quality (from which they can extract a lot of resources) and high vulnerability (from which it is easy to extract those resources). The paper goes on to suggest ways of predicting how antagonists will choose their victims and how this might be affected by global change. Mairenn presented this work to colleagues internationally at the European Society for Evolutionary Biology (ESEB) conference in Barcelona.
  • Tanmay Dixit coauthored a paper published in Behavioral Ecology on how all animals, from worms to hummingbirds to primates, discriminate between stimuli. The paper was led by Megan Worsley as part of her MSc at Imperial College London (ICL), and it was supervised by Tanmay and co-supervised by A/Prof. Julia Schroeder (ICL). Their meta-analysis showed that, on average, animals tend to discriminate between stimuli based on the proportional difference between them, rather than the absolute difference, which has interesting implications for the evolution of animal signals.
  • Tanmay Dixit and Claire Spottiswoode coauthored a paper, led by Dr Daniel Hanley (George Mason University, USA) and published in Biology Letters, on the chemical basis of colour in the amazingly diverse eggs of Tawny-flanked Prinias and the Cuckoo-finches that mimic them. This paper found that the relationships between pigment and colour are complex: while the pigmentary composition of eggshells predicts colour well for bluer eggshells, it does not do so for browner eggshells. Therefore, even though birds tend to only use two pigments in generating highly variable eggshell colours, there is much to learn about the complex ways in which these pigments are used to generate these colours.
  • Tanmay, along with Dr Andrew Catherall (University of Cambridge), published a Viewpoint paper in Ecology and Evolution discussing how highly complex animal behaviour could sometimes arise without the need for positive selection, counter to what is usually assumed.
  • Tanmay was a co-author on a Commentary paper in Journal of Experimental Biology, led by Prof. Eleanor Caves, detailing emerging frontiers in the field of visual ecology.
  • Tanmay also wrote four 'OutsideJEB' articles for the Journal of Experimental Biology: these articles summarised recently published and broadly interesting scientific papers for a non-technical audience.
  • Gabriel Jamie and Claire Spottiswoode published a paper in Evolution which, by way of a comparative analysis across species, found evidence of accelerated evolution of nestling ornamentation in parasitised lineages of finches (Estrildidae). This is the first evidence that these hosts and parasites are involved in a co-evolutionary arms race, with parasites mimicking the appearance of hosts’ nestlings and hosts evolving away from parasites. To gather the data for this research they collaborated with bird breeder Jelmer Huisman to assemble nestling mouth marking photos from as many species of estrildids as possible from around the world, as well as long-term collaborators Michael Sorenson and Prof. Rebecca Kilner (University of Cambridge).
  • Gabriel Jamie wrote a Viewpoint article for Nature Ecology & Evolution on ‘The Past and Future of Mimicry Research’ together with other researchers who work on mimicry. Gabriel’s piece focused on the evolution of multimodal mimicry and drew on his research into the parasitic interactions between indigobirds, whydahs and their hosts.
  • Mairenn Attwood and Claire Spottiswoode were co-authors of a new collaborative study on vocal communication in birds led by Dr Will Feeney and Dr James Kennerley, entitled ‘Learned use of an ancient sound–meaning association across hosts of avian brood parasites’, published in Nature Ecology and Evolution. The study shows how multiple hosts of brood parasites globally seem to have converged on similar alarm calls in response to brood parasites, assisting them to recruit other species in cooperative nest defence.
  • Jess Lund and Claire Spottiswoode were co-authors of a comparative study led by Dr Ekaterina Osipova and Prof. Tim Sackton (Harvard University) and Michael Sorenson on the population genomics of honeyguides, parasitic finches and cowbirds, finding evidence for convergent genomic adaptations associated with the transition from parental care to brood parasitism. The paper was published in Nature Ecology and Evolution.
  • Claire Spottiswoode collaborated with Michael Sorenson to write a Perspectives piece in Science on a study by Justin Merondun, Jochen Wolf and colleagues on the genomics of egg mimicry in Common Cuckoos.
  • The Zambia brood-parasite team continued their diverse outreach and collaborative activities internationally. In Choma, we ran sessions with students at Popota Primary School and with communities directly at the field site, while in the UK we ran sessions with students at the Thomas Clarkson Academy and the broader public at the Cambridge Zoology Museum. Maggie organised an art exhibition at the Livingstone Museum titled ‘Birds, Nests, Eggs & Cultural Tapestry’. Each artwork brings together natural science and cultural insight, offering a beautiful reminder of how our human story is intimately connected with the lives of birds. Gabriel held a successful bird identification training workshop, also in conjunction with the Livingstone Museum.
  • Teresa Abaurrea published the first paper from her PhD thesis, with co-authors Dr Angela Moreras and Robert Thomson, which explored whether Cuckoos select Redstart hosts of better quality to raise their offspring despite potential growth consequences for nestlings. The paper was published in Animal Behaviour.
  • Angela Moreras, Dr Jere Tolvanen, Robert Thomson and their collaborators from various institutions in Czechia authored a paper entitled ‘Can nest design hinder brood parasitism success?’, which came out in 2025 in the Journal of Avian Biology. 

Key co-supporters
Max Planck–UCT Centre for Behaviour and Coevolution; Natural Environment Research Council; Jesus College, Cambridge; Societas pro Fauna et Flora Fennica; Finnish Cultural Foundation; LUOVA Doctoral Programme in Wildlife Biology at the University of Helsinki.

Research team 2025
Team leaders and collaborators:
Prof. Claire Spottiswoode (FIAO, UCT / U. Cambridge)
A/Prof. Robert Thomson (FIAO, UCT)
Dr Gabriel Jamie (FIAO, UCT)
A/Prof. Susie Cunningham (FIAO, UCT)
Dr Chima Nwaogu (FIAO, UCT)
Dr Mairenn Attwood (FIAO, UCT)
Prof. Michael Sorenson (Boston University)
Dr Tanmay Dixit (U. Cambridge/FIAO, UCT)
Prof. Bart Kempenaers (Max Planck Institute for Biological Intelligence)
Dr Eunbi Kwon (Max Planck Institute for Biological Intelligence)
Dr Mihai Valcu (Max Planck Institute for Biological Intelligence)
Dr Wolfgang Forstmeier (Max Planck Institute for Biological Intelligence)
A/Prof. Rose Thorogood (U. Helsinki, Finland)
Dr Angela Moreras (Université Laval, Canada)
Dr Jere Tolvanen (U. Oulu, Finland)
Jessie Walton (FIAO, UCT)

Students:
Teresa Abaurrea (PhD, U. Helsinki); Jess Lund (PhD, Cambridge); Joel Radue (MSc, UCT); Maggie Mwale (PhD, UCT)

Field research team:
Silky Hamama, Collins Moya, Onest Siakwasia, Sylvester Munkonko, Sanigo Mwanza, Oscar Siakwasia, Iness Liteta, Milton Simanunki, Aron Muntanga and many others