Authors: Frank A. La Sorte| Kyle G. Horton| Cecilia Nilsson| Adriaan M. Dokter
Year: 2019
Publication: Global Change Biology
Publication Link: https://doi.org/10.1111/gcb.14531
Access: Open
Affiliations: Cornell Laboratory of Ornithology, Cornell University, Ithaca, New York
Corresponding Author: Frank A. La Sorte, Cornell Laboratory of Ornithology, Cornell University, Ithaca, NY. Email: fal42@cornell.edu
Funding: The Wolf Creek Charitable Foundation; National Science Foundation, Division of Biological Infrastructure. Grant Numbers: 1356308, 1661329; AWS Cloud Credits for Research
Keywords: global climate change, migration altitude, nocturnal migration, North America, seasonal bird migration, weather surveillance radar, wind assistance
Abstract: Current climate models and observations indicate that atmospheric circulation is being affected by global climate change. To assess how these changes may affect nocturnally migrating bird populations, we need to determine how current patterns of wind assistance at migration altitudes will be enhanced or reduced under future atmospheric conditions. Here, we use information compiled from 143 weather surveillance radars stations within the contiguous United States to estimate the daily altitude, density, and direction of nocturnal migration during the spring and autumn. We intersected this information with wind projections to estimate how wind assistance is expected to change during this century at current migration altitudes. The prevailing westerlies at midlatitudes are projected to increase in strength during spring migration and decrease in strength to a lesser degree during autumn migration. Southerly winds will increase in strength across the continent during both spring and autumn migration, with the strongest gains occurring in the center of the continent. Wind assistance is projected to increase across the central (0.44 m/s; 10.1%) and eastern portions of the continent (0.32 m/s; 9.6%) during spring migration, and wind assistance is projected to decrease within the central (0.32 m/s; 19.3%) and eastern portions of the continent (0.17 m/s; 6.6%) during autumn migration. Thus, across a broad portion of the continent where migration intensity is greatest, the efficiency of nocturnal migration is projected to increase in the spring and decrease in the autumn, potentially affecting time and energy expenditures for many migratory bird species. These findings highlight the importance of placing climate change projections within a relevant ecological context informed through empirical observations, and the need to consider the possibility that climate change may generate both positive and negative implications for natural systems.
Supplementary Material: At end of document
Intrusive Methodologies: None
Citizen Science: None
Conservation: Not discussed