Title: Flight response of slope‐soaring birds to seasonal variation in thermal generation

Abstract

Summary Animals respond to a variety of environmental cues, including weather conditions, when migrating. Understanding the relationship between weather and migration behaviour is vital to assessing time‐ and energy limitations of soaring birds. Different soaring modes have different efficiencies, are dependent upon different types of subsidized lift and are weather dependent. We collected GPS locations from 47 known‐age golden eagles that moved along 83 migration tracks. We paired each location with weather to determine meteorological correlates of migration during spring and fall as birds crossed three distinct ecoregions in north‐east North America. Golden eagle migration was associated with weather conditions that promoted thermal development, regardless of season, ecoregion or age. Eagle migration showed age‐ and season‐specific responses to weather conditions that promoted orographic lift. In spring, adult eagles migrated earlier, over fewer days, and under more variable weather conditions than did pre‐adults, suggesting that adults were time limited and pre‐adults made choices to conserve energy. In fall, we found no difference in the time span of migration or when each age class migrates; however, we saw evidence that pre‐adults were less efficient migrants than adults. The decision by soaring birds to migrate when thermals developed allowed individuals to manage trade‐offsmore » between migratory speed and migratory efficiency. When time was limited (i.e. spring movement of adults speeding towards nesting territories), use of whatever lift was available decreased the time span of migration. When migration was not time limited (e.g. spring movements by pre‐adults, all movements in fall), eagles avoided suboptimal flight conditions by pausing migration, thus increasing the time span of migration while reducing energetic costs.« less

Authors:

Duerr, Adam E. ^[1]; Miller, Tricia A. ^[1]; Lanzone, Michael ^[2]; Brandes, David ^[3]; Cooper, Jeff ^[4]; O'Malley, Kieran ^[5]; Maisonneuve, Charles ^[6]; Tremblay, Junior A. ^[7]; Katzner, Todd ^[8]; Franklin, ed., Craig

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+ Show Author Affiliations

1. Division of Forestry and Natural Resources West Virginia University 322 Percival Hall Morgantown West Virginia 26506 USA
2. Cellular Tracking Technologies LLC 2405 North Center Avenue Suite B Somerset Pennsylvania 15501 USA
3. Department of Civil and Environmental Engineering Acopian Engineering Center Lafayette College Easton Pennsylvania 18042 USA
4. Virginia Department of Game and Inland Fisheries 1320 Belman Road Fredericksburg Virginia 22401 USA
5. West Virginia Division of Natural Resources 1 Depot Street Romney West Virginia 26575 USA
6. Ministère du Développement durable, de l'Environnement, de la Faune et des Parcs 92 2e Rue Ouest Rimouski Québec G5L 8B3 Canada
7. Ministère du Développement durable, de l'Environnement, de la Faune et des Parcs 880 chemin Sainte‐Foy Québec City Québec G1S 4X4 Canada
8. Division of Forestry and Natural Resources West Virginia University 322 Percival Hall Morgantown West Virginia 26506 USA, United States Department of Agriculture, Forest Service Timber and Watershed Laboratory Parsons West Virginia 26287 USA

Publication Date:

Mon Dec 22 00:00:00 EST 2014

Sponsoring Org.:

USDOE

OSTI Identifier:

1401367

Grant/Contract Number:  

DE‐EE0003538

Resource Type:

Publisher's Accepted Manuscript

Journal Name:

Functional Ecology

Additional Journal Information:

Journal Name: Functional Ecology Journal Volume: 29 Journal Issue: 6; Journal ID: ISSN 0269-8463

Publisher:

Wiley-Blackwell

Country of Publication:

United Kingdom

Language:

English