title: Testing for effects of climate change on competitive relationships and coexistence between two bird species.
abstract: Climate change is expected to have profound ecological effects, yet shifts in competitive abilities among species are rarely studied in this context. Blue tits (Cyanistes caeruleus) and great tits (Parus major) compete for food and roosting sites, yet coexist across much of their range. Climate change might thus change the competitive relationships and coexistence between these two species. Analysing four of the highest-quality, long-term datasets available on these species across Europe, we extend the textbook example of coexistence between competing species to include the dynamic effects of long-term climate variation. Using threshold time-series statistical modelling, we demonstrate that long-term climate variation affects species demography through different influences on density-dependent and density-independent processes. The competitive interaction between blue tits and great tits has shifted in one of the studied sites, creating conditions that alter the relative equilibrium densities between the two species, potentially disrupting long-term coexistence. Our analyses show that long-term climate change can, but does not always, generate local differences in the equilibrium conditions of spatially structured species assemblages. We demonstrate how long-term data can be used to better understand whether (and how), for instance, climate change might change the relationships between coexisting species. However, the studied populations are rather robust against competitive exclusion.
authors.affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, PO Box 1066, Blindern, Oslo 0316, Norway n.c.stenseth@ibv.uio.no.
authors.forename: Nils Chr
authors.initials: NC
authors.lastname: Stenseth
authors.affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, PO Box 1066, Blindern, Oslo 0316, Norway.
authors.forename: Joël M
authors.identifier: http://orcid.org/0000-0002-1129-525X
authors.initials: JM
authors.lastname: Durant
authors.affiliation: Department of Biosciences, Swansea University, Singleton Park, Swansea SA2 8PP, UK Population Ecology Group, IMEDEA (CSIC-UIB), Institut Mediterrani d'Estudis Avançats C/ Miquel Marquès, 21, Esporles, Mallorca 07190, Spain.
authors.forename: Mike S
authors.identifier: http://orcid.org/0000-0003-1544-0407
authors.initials: MS
authors.lastname: Fowler
authors.affiliation: Evolutionary Ecology Group, University of Antwerp, Antwerp 2020, Belgium.
authors.forename: Erik
authors.initials: E
authors.lastname: Matthysen
authors.affiliation: Evolutionary Ecology Group, University of Antwerp, Antwerp 2020, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: Adriaensen
authors.affiliation: Department of Biology, Theoretical Population Ecology and Evolution Group, Lund University, Ecology Building, Lund 22362, Sweden.
authors.forename: Niclas
authors.initials: N
authors.lastname: Jonzén
authors.affiliation: Department of Statistics and Actuarial Science, University of Iowa, 263 Schaeffer Hall, Iowa City, IA 52242, USA.
authors.forename: Kung-Sik
authors.initials: KS
authors.lastname: Chan
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
authors.forename: Hai
authors.initials: H
authors.lastname: Liu
authors.affiliation: Terrestrial Ecology Unit, Department of Biology, Ghent University, K. L. Ledeganckstraat 35, Ghent 9000, Belgium.
authors.forename: Jenny
authors.initials: J
authors.lastname: De Laet
authors.affiliation: Edward Grey Institute, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
authors.forename: Ben C
authors.initials: BC
authors.lastname: Sheldon
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), PO Box 50, Wageningen 6700 AB, The Netherlands.
authors.forename: Marcel E
authors.initials: ME
authors.lastname: Visser
authors.affiliation: Evolutionary Ecology Group, University of Antwerp, Antwerp 2020, Belgium Laboratory of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA.
authors.forename: André A
authors.initials: AA
authors.lastname: Dhondt
mesh_terms: D000818:Animals; D057231:Climate Change; D003163:Competitive Behavior; D017753:Ecosystem; D005060:Europe; D015233:Models, Statistical; D046109:Passeriformes / Q000502:physiology*; D011156:Population Density; D011157:Population Dynamics
keywords: climate variation; coexistence and competitive exclusion; intra- and interspecific competition; statistical modelling; threshold modelling