Do winged animals like birds ever suffer comparable mishaps to those of human-made aircraft, such as aerodynamic stall, wing icing or hard landing?
Chris Woolf
St Neot, Cornwall, UK
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From observation, controlled flight into terrain seems to be the most common failure. As with human-controlled aircraft, when vision becomes unexpectedly confused, birds fly into things, such as windows, with terrible regularity. Geese seem good at water landings, but I have watched them topple ignominiously when hitting a piece of weed or ice that didn’t register in their flight plan.
As for stalling, birds seem to make a virtue of it rather than it being a mishap. I am impressed by seagulls intentionally stalling one wing in order to make a fast, over-the-shoulder attack, allowing them to roll steeply to grab the ice cream or pasty held in their victim’s opposite hand. Two-wing powered flight returns shortly after, with the risk of minimum altitude, as well as beak load, to contend with.
You can frequently watch birds such as jackdaws deterring predators – including buzzards – by climbing above them and stalling both wings to begin a plummeting drop onto the target. This is usually followed by another powered climb into a stall turn to attack again as quickly as possible.
John Ford
Amersham, Buckinghamshire, UK
I have watched murmurations of starlings, awestruck at their skill in formation flying. Then, one winter’s evening off the pier in Eastbourne, UK, I discovered they aren’t infallible. The lead bird took its flock perilously close to the sea and, either due to misjudgement or an unexpected gust of wind, disaster struck. A wing glanced the surface and in it tumbled, followed by hundreds of others.
In total disarray, they managed to extricate themselves and fly to the pier. Not to their roost below the pier, but to every available drying surface above. I feared that many of the bedraggled aviators wouldn’t survive the night.
Andy Douse
Drumnadrochit, Highlands, UK
All birds have to stall when landing, not having the benefit of a long runway to manage a controlled landing. The key to doing that safely is slowing themselves down to a speed that is low enough for them to perch or safely touch down on the ground. And yes, bird wings can and do ice up, which can be a serious problem when they are flying at or near their maximum weight, for example during migration, when they are carrying high fat loads to fuel such long flights.
Hard landings are also a common occurrence, especially in young birds learning to fly. Birds landing on ice can experience a similarly uncontrolled hard landing, and it is well known that swans and other waterfowl may mistake hard surfaces for water. This is often due to refraction in the air above hot surfaces, such as roads, and causes an unexpected and probably very hard landing. We can presume this is why we see so many reports of swans on motorways, especially in summer.
Mark Parker
Sway, Hampshire, UK
Some decades ago, while working in the Kalahari desert with a helicopter crew, I was living in a large caravan with a veranda. A black potter wasp, probably Delta emarginatum, built her mud nest inside an open cupboard in the caravan and began provisioning its cells with caterpillars. She captured this prey and paralysed them, then transported them to her nest, grasped in her legs below her body and held by her mandibles near the head end.
The third caterpillar she brought was several times her size and weight. The day was hot and still, at least 35°C (95°F), and inside the caravan, it was stiller and a few degrees hotter. She couldn’t remain airborne in the lower-density, hot interior air and made a forced landing below the nest, which was on the rear wall of the cupboard, about 10 centimetres above a shelf. She was able to stay aloft just above the shelf due to the extra lift generated by being near to the surface, known in aviation circles as ground effect, but she couldn’t generate enough lift to reach the nest.
After a few goes, she flew out of the caravan, still in ground effect, across the shelf and the floor, then circled to gain height in the cooler outside air, and returned to the caravan to try again, faster than previously, obviously hoping that her height and momentum would be sufficient to reach the nest. She was unsuccessful, but tried this a few times before giving up and abandoning the big caterpillar.
This potter wasp had evidently learned how to trade height for speed and how to make use of the ground effect. The helicopter crew found this to be a fascinating lesson in aerodynamics.
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