Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 112, Issue 46, Pages E6331-E6338Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1503381112
Keywords
migration; ecological barrier; Gulf of Mexico; songbirds; weather
Categories
Funding
- National Science Foundation (NSF) (IOS) [1147096, 1145952, 1147022]
- National Geographic Society Committee on Research and Exploration [897111]
- American Ornithologists' Union
- Birmingham Audubon Society
- Eastern Illinois University
- University of Illinois Urbana-Champaign
- University of Southern Mississippi
- NASA [NNX11AP61G]
- NSF [0947944]
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [1147022, 1146832] Funding Source: National Science Foundation
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [1145952] Funding Source: National Science Foundation
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Approximately two thirds of migratory songbirds in eastern North America negotiate the Gulf of Mexico (GOM), where inclement weather coupled with no refueling or resting opportunities can be lethal. However, decisions made when navigating such features and their consequences remain largely unknown due to technological limitations of tracking small animals over large areas. We used automated radio telemetry to track three songbird species (Red-eyed Vireo, Swainson's Thrush, Wood Thrush) from coastal Alabama to the northern Yucatan Peninsula (YP) during fall migration. Detecting songbirds after crossing similar to 1,000 km of open water allowed us to examine intrinsic (age, wing length, fat) and extrinsic (weather, date) variables shaping departure decisions, arrival at the YP, and crossing times. Large fat reserves and low humidity, indicative of beneficial synoptic weather patterns, favored southward departure across the Gulf. Individuals detected in the YP departed with large fat reserves and later in the fall with profitable winds, and flight durations (mean = 22.4 h) were positively related to wind profit. Age was not related to departure behavior, arrival, or travel time. However, vireos negotiated the GOM differently than thrushes, including different departure decisions, lower probability of detection in the YP, and longer crossing times. Defense of winter territories by thrushes but not vireos and species-specific foraging habits may explain the divergent migratory behaviors. Fat reserves appear extremely important to departure decisions and arrival in the YP. As habitat along the GOM is degraded, birds may be limited in their ability to acquire fat to cross the Gulf.
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