Original Research ARTICLE
Dynamic-parameter movement models reveal drivers of migratory pace in a soaring bird
- 1Department of Biology and Wildlife, College of Natural Science and Mathematics, University of Alaska Fairbanks, United States
- 2Department of Mathematics and Statistics, College of Natural Science and Mathematics, University of Alaska Fairbanks, United States
- 3Institute for the Oceans and Fisheries, University of British Columbia, Canada
- 4Department of Statistics, University of British Columbia, Canada
- 5Alaska Department of Fish and Game, United States
- 6United States Fish and Wildlife Service (USFWS), United States
- 7Institute of Arctic Biology, University of Alaska Fairbanks, United States
Long distance migration can increase lifetime fitness, but can be costly, incurring increased energetic expenses and higher mortality risks. Stopover and other en route behaviors allow animals to rest and replenish energy stores and avoid or mitigate other hazards during migration. Some animals, such as soaring birds, can subsidize the energetic costs of migration by extracting energy from flowing air. However, it is unclear how these energy sources affect or interact with behavioral processes and stopover in long-distance soaring migrants. To understand these behaviors and the effects of processes that might enhance use of flight subsidies, we developed a flexible mechanistic model to predict how flight subsidies drive migrant behavior and movement processes. The novel modeling framework incorporated time-varying parameters informed by environmental covariates to characterize a continuous range of behaviors during migration. This model framework was fit to GPS satellite telemetry data collected from a large soaring and opportunist foraging bird, the golden eagle (Aquila chrysaetos), during migration in western North America. Fitted dynamic model parameters revealed a clear circadian rhythm in eagle movement and behavior, which was directly related to thermal uplift. Behavioral budgets were complex, however, with evidence for a joint migrating/foraging behavior, resembling a slower paced fly-and-forage migration, which could facilitate efficient refueling while still ensuring migration progress. In previous work, ecological and foraging conditions are normally considered to be the key aspects of stopover location quality, but taxa, such as the golden eagle, that can tap energy sources from moving fluids to drive migratory locomotion may pace migration based on both foraging opportunities and available flight subsidies.
Keywords: Bayesian, correlated random walk, golden eagle, movement ecology, Soaring flight
Received: 11 Mar 2019;
Accepted: 07 Aug 2019.
Copyright: © 2019 Eisaguirre, Auger-Méthé, Barger, Lewis, Booms and Breed. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Mr. Joseph M. Eisaguirre, Department of Biology and Wildlife, College of Natural Science and Mathematics, University of Alaska Fairbanks, Fairbanks, 99775, Alaska, United States, email@example.com