Title: Effects of experimentally sustained elevated testosterone on incubation behaviour and 1 reproductive success in female great tits (Parus major) 2 Authors: Berber de Jong a,b,c , Luc Lens b , Seyed Mehdi Amininasab c,d , Kees van Oers e ,Veerle M. Darras f , 3 Marcel Eens g , Rianne Pinxten g,h , Jan Komdeur c & Ton G.G. Groothuis a 4 Affiliations: 5 a. Behavioural Biology, Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. 6 Box 11103, 9700 CC, Groningen, The Netherlands 7 b. Terrestrial Ecology Unit, Department Biology, Ghent University, BE-9000, Ghent, Belgium. 8 c. Behavioural and Physiological Ecology, Groningen Institute for ELIFES, University of Groningen, P.O. 9 Box 11103, 9700 CC, Groningen, The Netherlands 10 d. Department of Environmental Science, Behbahan Khatam Alanbia University of Technology, Iran 11 e. Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB, 12 Wageningen, The Netherlands 13 f. Laboratory of Comparative Endocrinology, K.U. Leuven, Naamsestraat 61, B-3000 Leuven, Belgium 14 g. Behavioural Ecology & Ecophysiology Research Group, Department of Biology, University of Antwerp, 15 Universiteitsplein 1, B-2610 Wilrijk, Belgium 16 h. Didactica Research Group, Faculty of Social Sciences, University of Antwerp, B-2000, Antwerp, 17 Belgium 18 Corresponding author: 19 Berber de Jong 20 Behavioural and Physiological Ecology 21 Groningen Institute for Evolutionary Life Sciences 22 University of Groningen, 23 P.O. Box 11103, 9700 CC, 24 Groningen, The Netherlands 25 Tel: +31-629478683 26 Email: berber.dejong@gmail.com 27 28