Time of emergence of novel climates for North American migratory bird populations

The procedure used to estimate time of emergence (ToE) of novel climates within (a) North America and (b) South America during the week of 4 January (blue) and 5 July (red). The thin colored lines are the probability estimates from the four atmosphere-ocean general circulation models (GCMs; Supplementary material Appendix 3 Table A2). These are the probabilities that the climate will be novel in relation to historical climates during a given week and location. The black dotted lines are the three probability thresholds considered in the analysis. The fitted colored lines and 95% confidence bands are from generalize additive mixed models with GCM included as a random effect (see Material and methods for details). ToE is identified as the year that the fitted GAMM crosses each probability threshold.

Authors: Frank A. La Sorte, Daniel Fink and Alison Johnston

Year: 2019

Publication: Ecogeography

Publication Link: https://doi.org/10.1111/ecog.04408

Full-text Access: Subscription

Affiliations: F. A. La Sorte (http://orcid.org/0000-0001-8521-2501) (fal42@cornell.edu), D. Fink (http://orcid.org/0000-0002-8368-1248) and A. Johnston (http://orcid.org/orcid.org/0000-0001-8221-013X), Cornell Laboratory of Ornithology, Cornell Univ., Ithaca, NY, USA. AJ also at: Dept of Zoology, Conservation Science Group, Univ. of Cambridge, Cambridge, UK.

Corresponding Author: F. A. La Sorte, fal42@cornell.edu

Funding: Funding received from National Science Foundation, Directorate for Biological Sciences, Division of Biological Infrastructure (ABI innovation: DBI-1661329, ABI sustaining: DBI-1356308), National Aeronautics and Space Administration (NNH12ZDA001N-ECOF), The Leon Levy Foundation and The
Wolf Creek Charitable Foundation. Computing support from the National Science Foundation (CNS-1059284 and CCF-1522054) and a Microsoft Azure Research Award (CRM: 0518680).

Keywords: annual cycle, eBird, global climate change, novel climates, seasonal bird migration, time of emergence

Abstract: To better understand the ecological implications of global climate change for species that display geographically and seasonally dynamic life-history strategies, we need to determine where and when novel climates are projected to first emerge. Here, we use a multivariate approach to estimate time of emergence (ToE) of novel climates based on three climate variables (precipitation, minimum and maximum temperature) at a weekly temporal resolution within the Western Hemisphere over a 280-yr period (2021–2300) under a high emissions scenario (RCP8.5). We intersect ToE estimates with weekly estimates of relative abundance for 77 passerine bird species that migrate between temperate breeding grounds in North America and southern tropical and
subtropical wintering grounds using observations from the eBird citizen-science database. During the non-breeding season, migrants that winter within the tropics are projected to encounter novel climates during the second half of this century. Migrants that winter in the subtropics are projected to encounter novel climates during the first half of the next century. During the beginning of the breeding season, migrants on their temperate breeding grounds are projected to encounter novel climates during the first half of the next century. During the end of the breeding season, migrants are projected to encounter novel climates during the second half of this century. Thus, novel climates will first emerge ca 40–50 yr earlier during the second half of the breeding season. These results emphasize the large seasonal and spatial variation in the formation of novel climates, and the pronounced challenges migratory birds are likely to encounter during this century, especially on their tropical wintering grounds and during the transition from breeding to migration. When assessing the ecological implications of climate change, our findings emphasize the value of applying a full annual cycle perspective using standardized metrics that promote comparisons across space and time.

Supplementary Materials: Available online as Appendix ecog-04408 at < www.ecography.org/appendix/ecog-04408 >. Appendix 1–4.

Intrusive Methodologies: None

Citizen Science: eBird data source

Conservation: Not discussed



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