Long-Distance Migratory Birds in Africa

Introduction

Great Reed Warbler

A Great Reed Warbler in Zambia, after it’s journey across the Sahara and a stop-over period in north-central Africa.

Many songbirds that breed in Europe migrate across the Sahara to spend the northern winter in tropical Africa, and many are known to be declining greatly in numbers globally. However, our understanding of their population growth and decline is limited by very sparse information on individual success during the non-breeding season in Africa. Dr Marjorie Sorensen studied the little-known African lives of Great Reed Warblers (Acrocephalus arundinaceus) and Willow Warblers (Phylloscopus trochilus) in Zambia during her PhD research. Here are some of the questions she addressed:

How do conditions at migratory staging sites affect winter success? Recently, miniaturised-light level geolocators have allowed small bodied migratory birds to be tracked for the first time, and migratory patterns to and from Africa to be illuminated. Surprisingly, rather than direct flights to single winter sites the use of multiple long-term staging sites is common. Staged migration complicates our understanding of population dynamics and raises questions about whether conditions experienced during staging may carry over to affect long term success.

Marjorie worked with Dr Jason Newton (Scottish Universities Environmental Research Centre), Dr Susanne Jenni-Eiermann (Swiss Ornithological Institute) and Dr Graham Fairhurst (University of Saskatchewan) to apply lab techniques in stable isotope, plasma metabolite, and stress hormone analysis to assess conditions experienced during staging and their possible consequences for winter success. Marjorie and team’s paper in BMC Ecology shows how environmental conditions at the Great Reed Warbler’s staging sites in the Horn of Africa appear to carry over to affect their condition at their final wintering site in Zambia.

Willow Warbler

A Willow Warbler radio-tagged by Marjorie Sorensen to establish whether despite its extravagant song, this species really is territorial on the non-breeding grounds in Africa. Read the answer here.

Why do migratory birds sing in winter?

Why do migratory birds sing in winter? High investment in expensive winter song is a puzzling behaviour for Palearctic-African migrants. Sixty-two percent of migratory songbird species sing on their wintering grounds in Africa, outside the context of breeding and mate attraction. While song quality during breeding is known to be important for overall fitness, the function of winter song has never been tested. Marjorie tested three competing hypothesis for winter song function: 1) the long-held territory defence hypothesis, that individuals sing for defence of winter feeding territories, 2) the testosterone hypothesis, that winter singing is a non-adaptive carry-over from elevated testosterone levels during breeding, and 3) the song improvement hypothesis, that winter singing functions to improve individual song quality and future reproductive success. Please see Marjorie’s papers on Willow Warblers (in Behavioural Ecology) and Great Reed Warblers (in The American Naturalist) singing in Africa, and these articles featuring her research in New Scientist, The AtlanticScience News and The Conversation; and listen to Marjorie discussing her work on the Canadian Broadcasting Corporation’s science programme, Quirks & Quarks.

Does avian malaria have negative consequences for wintering birds?

Avian malaria effects on host population dynamics in wild birds are poorly understood. This is due, in part, to the majority of studies taking place on European breeding grounds where birds have already entered the chronic stage of infection. While some slight negative effects of chronic infection have been documented for host fitness in Europe, understanding the consequences of avian malaria requires sampling individuals in areas of active parasite transmission. Some species-specific strains are transmitted in Africa and Marjorie worked with Dr Staffan Bensch (Lund University) to determine the type and intensity of these infections. Wintering birds may be in the acute stage of infection; therefore, sampling individuals in Zambia can provide valuable information on the effects of malaria infection for host winter success, survival, and population dynamics. See Majorie’s papers in Journal of Avian Biology and Ecology and Evolution for her answers so far.

Our migratory bird publications from Zambia

  • Sorensen, M.C., Dixit, T., Newton, J., Kardynal, K., Hobson, K., Bensch, S., Jenni-Eiereman, S. & Spottiswoode, C.N. 2019 Migration distance does not predict blood parasitism in a Palearctic-African migratory bird. Ecology and Evolution 9: 8294-8304. Read on journal website [Open Access]
  • Sorensen, M.C., Fairhurst, G.D., Jenni-Eiermann, D., Newton, J., Yohannes, E. & Spottiswoode, C.N. (2016) Seasonal rainfall at long-term migratory staging sites is associated with altered carry-over effects in a Palearctic-African migratory bird. BMC Ecology 16: 41. Read on journal website [Open Access]
  • Sorensen, M.C., Jenni-Eiermann, S. & Spottiswoode, C.N. (2016) Why do migratory birds sing on their tropical wintering grounds? American Naturalist187: E65–E76. Read on journal website
  • Sorensen, M.C., Asghar, M., Bensch, S., Fairhurst, G.D., Jenni-Eiermann, S. & Spottiswoode, C.N. (2016) A rare study from the wintering grounds provides insight into the costs of malaria infection for migratory birds. Journal of Avian Biology 57: 575–582. Read on journal website [Open Access]
  • El-Arabany, N., Sorensen, M.C. & Hansson, B. (2015) Inferring the links between breeding and wintering grounds in a Palearctic-African migratory bird, the Great Reed Warbler, using mitochondrial DNA data. African Zoology 50: 241-248.
  • Sorensen, M.C. (2014) Singing in Africa: no evidence for a long supposed function of winter song in a migratory songbird. Behavioral Ecology 25: 909-915. Read on journal website [Open Access]

… and from elsewhere

  • Spottiswoode, C.N. & Saino, N. (2010) Sexual selection and climate change. In: Møller, A.P., Fiedler, W. & Berthold, P. (Eds) Effects of Climate Change on Birds. Oxford University Press.
  • Coppack, T., Tøttrup, A.P. & Spottiswoode, C. (2006) Degree of protandry reflects level of extrapair paternity in migratory songbirds. Journal of Ornithology 147: 260-265.
  • Spottiswoode, C.N., Tøttrup, A.P. & Coppack, T. (2006) Sexual selection predicts advancement of avian spring migration in response to climate change. Proceedings of the Royal Society of London Series B 273: 3023-3029.
  • Spottiswoode, C. & Møller, A.P. (2004) Extra-pair paternity, migration and breeding synchrony in birds. Behavioral Ecology 15: 41-57.

News

Evolutionary Biology Crash Course

Tanmay Dixit was a member of a team organising and lecturing in the inaugural Evolutionary Biology Crash Course. This course, aimed at undergraduate or early-postgraduate students, teaches evolutionary principles to students who have had limited opportunities to be exposed to evolutionary ideas. The course is funded by the Equal Opportunities Initiative Fund of the European Society of Evolutionary Biology (ESEB). Tanmay presented lectures on behavioural ecology and evolution, focussing on kin selection, coevolution, and parasitism. Over 700 students, with the vast majority from the global South, attended the course, which was a resounding success!

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New paper on visual complexity & mimicry

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).

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Fieldwork and teaching at APLORI, Nigeria

Dr Gabriel Jamie is continuing his fieldwork on the evolution of polymorphisms in cisticolas and prinias in Nigeria, where he is also a teaching fellow at the AP Leventis Ornithological Research Institute (APLORI). The image shows the 2022 APLORI MSc class during the Global Birding Big Day on 14 May. The team recorded 135 species while walking around the nature reserve surrounding the institute.

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New paper on the genetics of cuckoo finch egg mimicry

Our paper “Genetic architecture facilitates then constrains adaptation in a host-parasite coevolutionary arms race” has been published in the Proceedings of the National Academy of Sciences of the USA. In it, we address the long-standing puzzle of how exquisite mimicry of the eggs of several different host species can evolve within a single species of brood-parasitic bird. We show that in cuckoo finches in Zambia, egg mimicry of different host egg phenotypes is maternally inherited, which allows mothers to transmit host-specific adaptations to their daughters irrespective of which host species the father was raised by. This study was a team effort from colleagues at the University of Cambridge and University of Cape Town (Claire Spottiswoode, Wenfei Tong, Gabriel Jamie), at Boston University (Katherine Stryjewski, Jeff DaCosta, Evan Kuras and Michael Sorenson) and in the Choma community in Zambia (Ailsa Green, Silky Hamama, Ian Taylor and Collins Moya).

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