Migrating birds avoid flying through fog and low clouds

Authors: M. Panuccio 1,2,3 & G. Dell’Omo 2 & G. Bogliani 3 & C. Catoni2 & N. Sapir 4

Year: 2019

Publication: International Journal of Biometeorology

Publication Link: https://doi.org/10.1007/s00484-018-01656-z

Access: Subscription

Affliations: 1 MEDRAPTORS (Mediterranean Raptor Migration Network), via
Mario Fioretti 18, 00152 Rome, Italy
2 Ornis Italica, piazza Crati 15, 00199 Rome, Italy
3 DSTA—Department of Earth and Environmental Sciences,
University of Pavia, via Ferrata 9, 27100 Pavia, Italy
4 Animal Flight Laboratory, Department of Evolutionary and
Environmental Biology, University of Haifa, 3498838 Haifa, Israel

Corresponding Author: M. Panuccio, panucciomichele@gmail.com

Funding: M.P. was partially financed through a grant from Crowdfunding Platform BUniversitiamo^ of the University of Pavia for the project BWings Over the Straits^.

Keywords: Avian long-distance migration . Bird flight . Ecological barrier . Fog . Radar . Soaring raptors

Abstract: Different weather conditions are known to affect bird migration, yet the influence of fog and low clouds on migrating birds has been rarely examined so far, and hence, their impact on bird movement is not well understood. Fog avoidance could be a consequence of visual limitations within the fog or may be the outcome of deteriorated soaring conditions due to the obstruction of the sun.We carried out a radar study at the Strait of Messina, which is a bottleneck for migrating birds traversing the Central Mediterranean Sea, to determine if the intensity of diurnal soaring bird migration was influenced by fog and other weather variables. We recorded bird movements using an X-band radar, which can detect birds flying within the fog, and recorded weather conditions using local meteorological observations. We examined if bird passage rate (number of tracks/hour) at the radar site was influenced by fog, wind speed and direction, air temperature and the time of day. Our findings suggest that fog was the most important factor affecting bird migration intensity as recorded by the radar, indicating that birds actively avoided flying into fog. In addition, wind direction affected bird migration intensity, with lower numbers recorded with southerly tailwinds and higher numbers recorded with westerly crosswinds. Our findings highlight a consequence of widespread meteorological conditions, and of fog in particular, on migrating birds, with implications for bird migration navigation, path length and flight energetics.

Electronic Supplementary Material: The online version of this article (https://doi.org/10.1007/s00484-018-01656-z) contains supplementary material, which is available to authorized users.

Intrusive Methodologies: None

Citizen Science: None

Conservation: “Our findings may also be used to investigate the impact of human-built structures on birds, particularly during migration and other movements, which is of crucial importance for bird conservation (Hüppop et al. 2006; Lambertucci et al. 2015). In particular, collision risks of birds with man-made structures like wind turbines depend on different factors, among which are weather conditions. Specifically, collision prevalence increases when visibility is poor (Drewitt and Langston 2006), and therefore, this must be taken it into account when estimating collision risks in areas where fog is common.We suggest directing future research on exploring the behavioural responses of soaring versus flapping migrants under different visibility conditions because these two groups may respond differently to these conditions due to the critical role of updrafts for soaring flight, possibly leading to differences in risks of collision with man-made structures. Future studies may also explore how specific movement and flight behaviour attributes such as altitude choice, flight speed and path tortuosity vary under different weather conditions.”

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