Interaction of climate change with effects of conspecific and heterospecific density on reproduction

Møller, A.P. and Balbontín, J. and Dhondt, A.A. and Adriaensen, F. and Artemyev, A. and Bańbura, J. and Barba, E. and Biard, C. and Blondel, J. and Bouvier, J.-C. and Camprodon, J. and Cecere, F. and Charter, M. and Cichoń, M. and Cusimano, C. and Dubiec, A. and Eens, M. and Eeva, T. and Ferns, P.N. and Forsman, J.T. and Goldshtein, A. and Goodenough, A.E. and Gosler, A.G. and Gustafsson, L. and Harnist, I. and Hartley, I.R. and Heeb, P. and Hinsley, S.A. and Jacob, S. and Järvinen, A. and Juškaitis, R. and Korpimäki, E. and Krams, I. and Laaksonen, T. and Leclercq, B. and Lehikoinen, E. and Loukola, O. and Mainwaring, M.C. and Mänd, R. and Massa, B. and Matthysen, E. and Mazgajski, T.D. and Merino, S. and Mitrus, C. and Mönkkönen, M. and Nager, R.G. and Nilsson, J.-Å. and Nilsson, S.G. and Norte, A.C. and von Numers, M. and Orell, M. and Pimentel, C.S. and Pinxten, R. and Priedniece, I. and Remeš, V. and Richner, H. and Robles, H. and Rytkönen, S. and Senar, J.C. and Seppänen, J.T. and da Silva, L.P. and Slagsvold, T. and Solonen, T. and Sorace, A. and Stenning, M.J. and Török, J. and Tryjanowski, P. and van Noordwijk, A.J. and Walankiewicz, W. and Lambrechts, M.M. (2020) Interaction of climate change with effects of conspecific and heterospecific density on reproduction. Oikos, 129 (12). pp. 1807-1819. ISSN 0030-1299

Abstract

We studied the relationship between temperature and the coexistence of great tit Parus major and blue tit Cyanistes caeruleus, breeding in 75 study plots across Europe and North Africa. We expected an advance in laying date and a reduction in clutch size during warmer springs as a general response to climate warming and a delay in laying date and a reduction in clutch size during warmer winters due to density-dependent effects. As expected, as spring temperature increases laying date advances and as winter temperature increases clutch size is reduced in both species. Density of great tit affected the relationship between winter temperature and laying date in great and blue tit. Specifically, as density of great tit increased and temperature in winter increased both species started to reproduce later. Density of blue tit affected the relationship between spring temperature and blue and great tit laying date. Thus, both species start to reproduce earlier with increasing spring temperature as density of blue tit increases, which was not an expected outcome, since we expected that increasing spring temperature should advance laying date, while increasing density should delay it cancelling each other out. Climate warming and its interaction with density affects clutch size of great tits but not of blue tits. As predicted, great tit clutch size is reduced more with density of blue tits as temperature in winter increases. The relationship between spring temperature and density on clutch size of great tits depends on whether the increase is in density of great tit or blue tit. Therefore, an increase in temperature negatively affected the coexistence of blue and great tits differently in both species. Thus, blue tit clutch size was unaffected by the interaction effect of density with temperature, while great tit clutch size was affected in multiple ways by these interactions terms.