Journal of Biogeography. 2019;00:1–13. wileyonlinelibrary.com/journal/jbi | 1 © 2019 John Wiley & Sons Ltd Received: 22 November 2018 | Revised: 8 July 2019 | Accepted: 22 July 2019 DOI: 10.1111/jbi.13688 RESEARCH PAPER Forest structure determines spatial changes in avian communities along an elevational gradient in tropical Africa David Hořák 1 | Michal Ferenc 1 | Ondřej Sedláček 1 | Francis Njie Motombi 2 | Miroslav Svoboda 3 | Jan Altman 4 | Tomáš Albrecht 5,6 | Eric Djomo Nana 1,7,8 | Štěpán Janeček 1,4 | Martin Dančák 9 | Ľuboš Majeský 10 | Elias Ndive Lltonga 11 | Jiří Doležal 4,12 1 Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic 2 Mt Cameroon NP, Buea, Cameroon 3 Department of Forest Ecology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Prague, Czech Republic 4 Institute of Botany, The Czech Academy of Sciences, Průhonice, Czech Republic 5 Institute of Vertebrate Biology, The Czech Academy of Sciences, Brno, Czech Republic 6 Department of Zoology, Faculty of Science, Charles University, Prague, Czech Republic 7 Congo Basin Institute, Yaoundé, Cameroon 8 Institute of Agricultural Research for Development - IRAD, Yaoundé, Cameroon 9 Department of Ecology and Environmental Sciences, Faculty of Science, Palacký University in Olomouc, Olomouc-Holice, Czech Republic 10 Department of Botany, Faculty of Science, Palacký University in Olomouc, Olomouc-Holice, Czech Republic 11 Limbe Botanic Garden, Limbe, Cameroon 12 Department for Botany, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic Correspondence David Hořák, Department of Ecology, Faculty of Science, Charles University, Viničná 7, CZ-128 44 Prague, Czech Republic. Email: david.horak@natur.cuni.cz Funding information Czech Science Foundation, Grant/Award Number: 14-36098G and 17-19376S Handling Editor: Camila Ribas Abstract Aim: To test if tree species richness and forest structure drive spatial variation in avian communities along a tropical elevation gradient and to present information about the role of detailed forest parameters. Location: A 2,000-m long elevational gradient of tropical forest on Mt. Cameroon, west-central Africa. Taxon: Birds and trees. Methods: We performed bird censuses and vegetation mapping at the same plots across six forested sites at elevations of 350, 650, 1,100, 1,500, 1,850, and 2,200 m a.s.l., with 16 plots per elevation. We tested the effects of elevation, forest structure and tree diversity on the species richness, functional diversity and β-diversity of birds (Bray–Curtis dissimilarity). We used conditional inference trees based on random for- ests (RF) to investigate these relationships across all elevation sites as well as within elevations. Results: Both tree and bird species richness declined monotonically with eleva- tion. Vegetation structure correlated with elevation, and all vegetation attributes