title: Challenging claims in the study of migratory birds and climate change.
abstract: Recent shifts in phenology in response to climate change are well established but often poorly understood. Many animals integrate climate change across a spatially and temporally dispersed annual life cycle, and effects are modulated by ecological interactions, evolutionary change and endogenous control mechanisms. Here we assess and discuss key statements emerging from the rapidly developing study of changing spring phenology in migratory birds. These well-studied organisms have been instrumental for understanding climate-change effects, but research is developing rapidly and there is a need to attack the big issues rather than risking affirmative science. Although we agree poorly on the support for most claims, agreement regarding the knowledge basis enables consensus regarding broad patterns and likely causes. Empirical data needed for disentangling mechanisms are still scarce, and consequences at a population level and on community composition remain unclear. With increasing knowledge, the overall support ('consensus view') for a claim increased and between-researcher variability in support ('expert opinions') decreased, indicating the importance of assessing and communicating the knowledge basis. A proper integration across biological disciplines seems essential for the field's transition from affirming patterns to understanding mechanisms and making robust predictions regarding future consequences of shifting phenologies.
authors.affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Norway.
authors.forename: Endre
authors.initials: E
authors.lastname: Knudsen
authors.forename: Andreas
authors.initials: A
authors.lastname: Lindén
authors.forename: Christiaan
authors.initials: C
authors.lastname: Both
authors.forename: Niclas
authors.initials: N
authors.lastname: Jonzén
authors.forename: Francisco
authors.initials: F
authors.lastname: Pulido
authors.forename: Nicola
authors.initials: N
authors.lastname: Saino
authors.forename: William J
authors.initials: WJ
authors.lastname: Sutherland
authors.forename: Lars A
authors.initials: LA
authors.lastname: Bach
authors.forename: Timothy
authors.initials: T
authors.lastname: Coppack
authors.forename: Torbjørn
authors.initials: T
authors.lastname: Ergon
authors.forename: Phillip
authors.initials: P
authors.lastname: Gienapp
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Gill
authors.forename: Oscar
authors.initials: O
authors.lastname: Gordo
authors.forename: Anders
authors.initials: A
authors.lastname: Hedenström
authors.forename: Esa
authors.initials: E
authors.lastname: Lehikoinen
authors.forename: Peter P
authors.initials: PP
authors.lastname: Marra
authors.forename: Anders P
authors.initials: AP
authors.lastname: Møller
authors.forename: Anna L K
authors.initials: AL
authors.lastname: Nilsson
authors.forename: Guillaume
authors.initials: G
authors.lastname: Péron
authors.forename: Esa
authors.initials: E
authors.lastname: Ranta
authors.forename: Diego
authors.initials: D
authors.lastname: Rubolini
authors.forename: Tim H
authors.initials: TH
authors.lastname: Sparks
authors.forename: Fernando
authors.initials: F
authors.lastname: Spina
authors.forename: Colin E
authors.initials: CE
authors.lastname: Studds
authors.forename: Stein A
authors.initials: SA
authors.lastname: Saether
authors.forename: Piotr
authors.initials: P
authors.lastname: Tryjanowski
authors.forename: Nils Chr
authors.initials: NC
authors.lastname: Stenseth
mesh_terms: D025041:Animal Migration; D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000502:physiology*; D057231:Climate Change; D012621:Seasons