9 research outputs found
The interplay of wind and uplift facilitates over-water flight in facultative soaring birds.
Flying over the open sea is energetically costly for terrestrial birds. Despite this, over-water journeys of many birds, sometimes hundreds of kilometres long, are uncovered by bio-logging technology. To understand how these birds afford their flights over the open sea, we investigated the role of atmospheric conditions, specifically wind and uplift, in subsidizing over-water flight at a global scale. We first established that ΔT, the temperature difference between sea surface and air, is a meaningful proxy for uplift over water. Using this proxy, we showed that the spatio-temporal patterns of sea-crossing in terrestrial migratory birds are associated with favourable uplift conditions. We then analysed route selection over the open sea for five facultative soaring species, representative of all major migratory flyways. The birds maximized wind support when selecting their sea-crossing routes and selected greater uplift when suitable wind support was available. They also preferred routes with low long-term uncertainty in wind conditions. Our findings suggest that, in addition to wind, uplift may play a key role in the energy seascape for bird migration that in turn determines strategies and associated costs for birds crossing ecological barriers such as the open sea
Match between soaring modes of black kites and fine-scale distribution on updrafts
Understanding how soaring birds use updrafts at small spatial scales is important to identify ecological
constraints of movement, and may help to prevent conflicts between wind-energy development and
the conservation of wildlife. We combined high-frequency GPS animal tracking and fine-spatial-scale
uplift modelling to establish a link between flight behaviour of soaring birds and the distribution
of updrafts. We caught 21 black kites (Milvus migrans) and GPS-tracked them while flying over the
Tarifa region, on the Spanish side of the Strait of Gibraltar. This region has a diverse topography and
land cover, favouring a heterogeneous updraft spatial distribution. Bird tracks were segmented and
classified into flight modes from motion parameters. Thermal and orographic uplift velocities were
modelled from publically available remote-sensing and meteorological data. We found that birds
perform circular soaring in areas of higher predicted thermal uplift and linear soaring in areas of higher
predicted orographic uplift velocity. We show that updraft maps produced from publically available data
can be used to predict where soaring birds will concentrate their flight paths and how they will behave
in flight. We recommend the use of this methodological approach to improve environmental impact
assessments of new wind-energy installationsinfo:eu-repo/semantics/publishedVersio