Air traffic has increased significantly in recent years, from 1.674 billion passengers in 2000 to 4.397 billion passengers in 2019. However, this growth has come at a cost. In their latest research, Arrondo et al. review and quantify the characteristics of bird strikes in Spain, and analyse flight patterns of the species that caused aircraft crashes in Europe.
Bird strikes have been a feature of air travel since the invention of the very first motor-operated airplane – the Wright brothers collided with a seagull in 1903, just one year after patenting their invention.
Today, collisions between aircrafts and birds number in the tens of thousands annually. Most bird strikes are minor, but some can cause considerable economic losses due to aircraft damage or worse, lead to human fatalities.
Preventing bird strikes is a priority for aviation authorities. Localized mitigation measures have been effective at minimizing general risks, as most bird strikes occur during takeoff or landing. However, mitigating en-route bird strikes is more complicated because there is a lack of information on the space use of the birds involved.
En-route bird strikes are especially dangerous for general aviation as they usually involve small air crafts that crash more easily after a collision, especially if the bird is large.
In Europe for example, according to official data from the European Aviation Safety Agency, 12 aircraft have crashed since the year 2000, all of them small and all belonging to general aviation – causing a total of 15 fatalities. Moreover, all of these bird strikes occurred en-route and were caused by large birds in Spain (griffon vulture, cinereous and white stork).
Thanks to technological improvements in GPS tracking, it is now possible to know the exact flight patterns of these species and therefore work out how they interfere with aviation. With this in mind, we collected GPS information on 210 individuals of the three species mentioned above (92 griffon vulture, 15 cinereous vulture and 103 white stork) between 2006-2019 and analysed their daily and annual flight patterns.
Our results showed that these species are more active in the central hours (10:00-16:00 UTC) of the warmest months (March to September) – the same period where most of the bird strikes occurred.
The three species reached maximum flight heights of over 1500 meters above the ground – 1,931 m griffon vulture 1,646 m cinereous vulture and 2,287 m white stork, but 99% of their activity was below 1,253 m – overlapping fully with the air band in which, according to current legislation, general aviation is required to fly.
It seems clear therefore that en-route collisions occur because general aviation and these species fly not only in the same period of the year and at the same times, but also in the same air column.
Our findings indicate that it would be desirable for aviation authorities to reconsider the flight ceiling of general aviation and to adapt it to the ecological conditions of certain species. However, this is a difficult and slow legislative change, and our results should also serve to provide recommendations to pilots that allow them to take precautions at periods with the highest risk, such as flying higher or reducing speed to minimize the kinetic energy of a possible impact.
Finally, and perhaps most importantly, this work demonstrates that the study of ecology not only serves to conserve biodiversity, which in and of itself is an important objective, but something which can be applied to a real world problem that could potentially save lives.
Read the full paper Use of avian GPS tracking to mitigate human fatalities from bird strikes caused by large soaring birds in Journal of Applied Ecology.