Seagulls in city centres could be used to plan drone flight routes

Seagulls plague many city dwellers. For many, seagulls are worse than rats or pigeons. They steal sandwiches, tear up garbage bags, and even eat them. It’s interesting to note that herring gulls and lesser-black-backed gulls are decreasing in rural areas while increasing in urban ones.

There are many reasons for this, including easy access to food and nesting sites, as well as a tolerance of humans. In our study that was recently published, the ease of flying might make city centers an attractive option for birds.

Turbulent skies

It can be hard for us to imagine the feeling of traveling in a medium that is moving. It is easier to glide through water in a pool if you are swimming alone. Other swimmers have not stirred up the water. It’s not a big deal, but imagine how you would feel if you were swimming in a sea where the tide could pull you back.

Imagine that you would have to swim every day through the ocean to get to your workplace. The currents can be in your favor or against you. This, along with the choppy nature of the water, will determine how hard you need to work. You would become adept at predicting sea conditions and current directions if you did this every day. The air is never still, and this affects the flight behavior of flying animals.

Our study examined how gulls fly without flapping by using the rising air created by buildings. We conducted our study in the seaside town of Swansea and found that the gulls alter their flight patterns to take advantage of updraughts around hotels along the bay.

These energy-saving strategies have been widely studied in birds who undertake their annual migrations. However, they are not as well known as birds that move around every day.

Tracking gulls

We used laser-range-finding binoculars in order to record the flight path of the gulls as they soared on the rising air produced by the hotels. This was combined with a computer model that simulated the movement of air around the hotels on the seafront and the flight characteristics of the gulls. The results suggested that gulls adopt a flight strategy that allows them to maintain greater control when faced with cross-wind gusts.

Even small artificial structures, such as hotels that are only a few stories high, can alter bird flight patterns by changing airflows. Urban areas can be associated with low flight costs because buildings allow for ample airflow in all weather conditions.

However, taking advantage of urban airflows to get cheap rides is not without risk. Airflows are very complex in environments with difficult substrates, such as urban areas. To account for this, in order to determine whether the positions of the gulls changed with the increase in wind strength, we mapped their exact locations relative to the airflows above the hotels.

Flying ahead

This fascinating flight strategy can be used to plan flight paths of uncrewed aerial vehicles or drones in urban landscapes.

Our results demonstrate that even the airflow around small features can have profound effects on energy consumption and flight control for birds and drones. We knew that, in this case, and many others to come, biologists and engineers would benefit from working together.

The wind speed of small-scale UAVs, which have fixed wings like conventional aircraft, is similar to the airspeed. This means that they are more affected by turbulence and gusts. Most autonomous flight control systems are not designed to handle flying at low altitudes in urban environments with a highly complex flow pattern close to buildings and terrain. In order to develop flight control systems and plan UAV flight paths, it would be useful to examine how birds with similar weights and sizes overcome these challenges.

Next time you feel ill towards gulls flying in the city, perhaps shielding your ice cream as you walk along the seafront, stop for a minute to appreciate the complex choices that these feathered aviators are making second by second as they react to their constantly changing aerial environment in ways that engineers, at this point, can only dream about.