Abstract
Background: In-flight conditions are hypothesized to influence the timing and success of long-distance migration. Wind assistance and thermal uplift are thought to reduce the energetic costs of flight, humidity, air pressure and temperature may affect the migrants’ water balance, and clouds may impede navigation. Recent advances in animal-borne long-distance tracking enable evaluating the importance of these factors in determining animals’ flight altitude.
Methods: Here we determine the effects of wind, humidity, temperature, cloud cover, and altitude (as proxy for climbing costs and air pressure) on flight altitude selection of two long-distance migratory shorebirds, far eastern curlew (Numenius madagascariensis) and whimbrel (Numenius phaeopus). To reveal the predominant drivers of flight altitude selection during migration we compared the atmospheric conditions at the altitude the birds were found flying with conditions elsewhere in the air column using conditional logistic mixed effect models.
Results: Our results demonstrate that despite occasional high-altitude migrations (up to 5550 m above ground level), our study species typically forego flying at high altitudes, limiting climbing costs and potentially alleviating water loss and facilitating navigation. While mainly preferring migrating at low altitude, notably in combination with low air temperature, the birds also preferred flying with wind support to likely reduce flight costs. They avoided clouds, perhaps to help navigation or to reduce the risks from adverse weather.
Conclusions: We conclude that the primary determinant of avian migrant’s flight altitude selection is a preference for low altitude, with wind support as an important secondary factor. Our approach and findings can assist in predicting climate change effects on migration and in mitigating bird strikes with air traffic, wind farms, power lines, and other human-made structures.
| Original language | English |
|---|---|
| Article number | 32 |
| Pages (from-to) | 1-12 |
| Number of pages | 12 |
| Journal | Movement Ecology |
| Volume | 9 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 13 Jun 2021 |
Bibliographical note
Funding Information:We acknowledge and thank the Traditional Owners of the land on which our research was conducted ? the Larrakia People, the Yawuru People, the Quandamooka People and the Boon Wurrung People. We thank the Australasian Wader Studies Group, the Victorian Wader Study Group and the Queensland Wader Study Group and all the volunteers that helped in the field to catch far eastern curlew and whimbrel, with a special thanks to Chris J. Hassell, Kar-Sin K. Leung, Grace Maglio and Roz Jessop. This research received support and funding from Darwin Port and the University of Queensland. Department of Transport and Main Roads, Moreton Bay Regional Council, and Redland City Council provided access to sites in Queensland. Darwin Port and Genesee Wyoming Australia gave access to sites in the Northern Territory. ?ke Lindstr?m and two anonymous reviewers are thanked for their constructive comments on earlier versions of this manuscript.
Funding Information:
We acknowledge and thank the Traditional Owners of the land on which our research was conducted – the Larrakia People, the Yawuru People, the Quandamooka People and the Boon Wurrung People. We thank the Australasian Wader Studies Group, the Victorian Wader Study Group and the Queensland Wader Study Group and all the volunteers that helped in the field to catch far eastern curlew and whimbrel, with a special thanks to Chris J. Hassell, Kar-Sin K. Leung, Grace Maglio and Roz Jessop. This research received support and funding from Darwin Port and the University of Queensland. Department of Transport and Main Roads, Moreton Bay Regional Council, and Redland City Council provided access to sites in Queensland. Darwin Port and Genesee Wyoming Australia gave access to sites in the Northern Territory. Åke Lindström and two anonymous reviewers are thanked for their constructive comments on earlier versions of this manuscript.
Funding Information:
This research received support from the Australian Government’s National Environmental Science Program through the Threatened Species Recovery Hub, an Australian Government Endeavour Leadership Program scholarship (to BG) and the Australian Research Council (DP190101861 to MK) and the National Natural Science Foundation of China (31830089 and 31772467 to ZM).
Publisher Copyright:
© 2021, The Author(s).
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
