Flight altitude of trans-Sahara migrants in autumn: a comparison of radar observations with predictions from meteorological conditions and water and energy balance models

Klaassen, Marcel and Biebach, Herbert 2000, Flight altitude of trans-Sahara migrants in autumn: a comparison of radar observations with predictions from meteorological conditions and water and energy balance models, Journal of avian biology, vol. 31, no. 1, pp. 47-55, doi: 10.1034/j.1600-048X.2000.310107.x.

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Title Flight altitude of trans-Sahara migrants in autumn: a comparison of radar observations with predictions from meteorological conditions and water and energy balance models
Author(s) Klaassen, MarcelORCID iD for Klaassen, Marcel orcid.org/0000-0003-3907-9599
Biebach, Herbert
Journal name Journal of avian biology
Volume number 31
Issue number 1
Start page 47
End page 55
Total pages 9
Publisher Wiley
Place of publication London, Eng.
Publication date 2000-03
ISSN 0908-8857
Keyword(s) Science & Technology
Life Sciences & Biomedicine
Ornithology
Zoology
MIGRATING BIRDS
THRUSH NIGHTINGALE
LUSCINIA-LUSCINIA
LIMITATIONS
EXPENDITURE
ISRAEL
RANGE
Summary Radar observations on the altitude of bird migration and altitudinal profiles of meteorological conditions over the Sahara desert are presented for the autumn migratory period. Migratory birds fly at an average altitude of 1016 m (a.s.l.) during the day and 571 m during the night. Weather data served to calculate flight range using two models: an energy model (EM) and an energy-and-water model (EWM). The EM assumes that fuel supply limits flight range whereas the EWM assumes that both fuel and water may limit flight range. Flight ranges estimated with the EM were generally longer than those with the EWM. This indicates that trans-Sahara migrants might have more problems balancing their water than their energy budget. However, if we assume fuel stores to consist of 70% instead of 100% fat (the remainder consisting of 9% protein and 21% water), predicted flight ranges of the EM and EWM largely overlap. Increased oxygen extraction, reduced flight costs, reduced exhaled air temperature, reduced cutaneous water loss and increased tolerance to water loss are potential physiological adaptations that would improve the water budget in migrants. Both the EM and EWM predict optimal flight altitudes in agreement with radar observations in autumn. Optimal flight altitudes are differently predicted by the EM and EWM for nocturnal spring migration. During spring, the EWM predicts moderately higher and the EM substantially higher flight altitudes than during autumn. EWM predictions are therefore in better agreement with radar observations on flight altitude of migrants over the Negev desert in spring than EM predictions.
Language eng
DOI 10.1034/j.1600-048X.2000.310107.x
Field of Research 060299 Ecology not elsewhere classified
Socio Economic Objective 970105 Expanding Knowledge in the Environmental Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2000, Wiley
Persistent URL http://hdl.handle.net/10536/DRO/DU:30075856

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