Taxon:
Milvus migrans

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Scientific Name
Milvus migrans
Common Name
Black Kite
Taxa Group
Accipitridae
Environment
Move Mode

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2019 - 20202
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Author: Silva, João Paulo ×

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Now showing 1 - 2 of 2
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    Data package
    Data from: The gateway to Africa: what determines sea crossing performance of a migratory soaring bird at the strait of Gibraltar?
    (2020-03-08) Santos, Carlos David; Silva, João Paulo; Muñoz, Antonio-Román; Onrubia, Alejandro; Wikelski, Martin
    (1) Large bodies of water represent major obstacles for the migration of soaring birds because thermal updrafts are absent or weak over water. Soaring birds are known to time their water crossings with favourable weather conditions and there are records of birds falling into the water and drowning in large numbers. However, it is still unclear how environmental factors, individual traits and trajectory choices affect their water crossing performance, this being important to understand the fitness consequences of water barriers for this group of birds. (2) We addressed this problem using the black kite (Milvus migrans) as model species at a major migration bottleneck, the Strait of Gibraltar. (3) We recorded high‐resolution GPS and triaxial accelerometer data for 73 birds while crossing the Strait of Gibraltar, allowing the determination of sea crossing duration, length, altitude, speed and tortuosity, the flapping behaviour of birds and their failed crossing attempts. These parameters were modelled against wind speed and direction, time of the day, solar irradiance (proxy of thermal uplift), starting altitude and distance to Morocco, and age and sex of birds. (4) We found that sea crossing performance of black kites is driven by their age, the wind conditions, the starting altitude and distance to Morocco. Young birds made longer sea crossings and reached lower altitude above the sea than adults. Crosswinds promoted longer sea crossings, with birds reaching lower altitudes and with higher flapping effort. Birds starting at lower altitudes were more likely to quit or made higher flapping effort to complete the crossing. The location where birds started the sea crossings impacted crossing distance and duration. (5) We present evidence that explains why migrating soaring birds accumulate at sea passages during adverse weather conditions. Strong crosswinds during sea crossings force birds to extended flap‐powered flight at low altitude, which may increase their chances of falling in the water. We also showed that juvenile birds assume more risks than adults. Finally, the way in which birds start the sea crossing is crucial for their success, particularly the starting altitude, which dictates how far birds can reach with reduced flapping effort.
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    Data package
    Data from: Wind farm turbines cause functional habitat loss for migratory soaring birds
    (2019-02-21) Marques, Ana Teresa; Santos, Carlos David; Hanssen, Frank; Muñoz, Antonio-Román; Onrubia, Alejandro; Wikelski, Martin; Moreira, Francisco; Palmeirim, Jorge Manuel; Silva, João Paulo
    NOTE: An updated and larger version of this dataset is available. See https://doi.org/10.5441/001/1.23n2m412. ABSTRACT: (1) Wind energy production has expanded to meet climate change mitigation goals, but negative impacts of wind turbines have been reported on wildlife. Soaring birds are among the most affected groups with alarming fatality rates by collision with wind turbines and an escalating occupation of their migratory corridors. These birds have been described as changing their flight trajectories to avoid wind turbines, but this behaviour may lead to functional habitat loss, as suitable soaring areas in the proximity of wind turbines will likely be underused. (2) We modelled the displacement effect of wind turbines on black kites (Milvus migrans) tracked by GPS. We also evaluated the impact of this effect at the scale of the landscape by estimating how much suitable soaring area was lost to wind turbines. (3) We used state‐of‐art tracking devices to monitor the movements of 130 black kites in an area populated by wind turbines, at the migratory bottleneck of the Strait of Gibraltar. Landscape use by birds was mapped from GPS data using dynamic Brownian bridge movement models and generalized additive mixed modelling was used to estimate the effect of wind turbine proximity on bird use while accounting for orographic and thermal uplift availability. (4) We found that areas up to approximately 674 m away from the turbines were less used than expected given their uplift potential. Within that distance threshold, bird use decreased with the proximity to wind turbines. We estimated that the footprint of wind turbines affected 3‐14% of the areas suitable for soaring in our study area. (5) We present evidence that the impacts of wind energy industry on soaring birds are greater than previously acknowledged. In addition to the commonly reported fatalities, the avoidance of turbines by soaring birds causes habitat losses in their movement corridors. Authorities should recognize this further impact of wind energy production and establish new regulations that protect soaring habitat. We also showed that soaring habitat for birds can be modelled at a fine scale using publicly available data. Such an approach can be used to plan low‐impact placement of turbines in new wind energy developments.