Lovebirds land on a flying trapeze with the greatest of ease Free

As the children's song says, trapeze artists ‘fly through the air with the greatest of ease’. This statement might be true while they are soaring from bar to bar, but trapeze artists need to time their release perfectly so that they meet the oncoming bar as it slows down and then brace themselves for impact or risk falling from death-defying heights. In nature, birds need similar grace when coming in to land on a branch that's swaying in the wind. So, how do these feathered trapeze artists approach a swinging perch and stop themselves from toppling over it when they want to land? With this question in mind, Partha Bhagavatula and Andrew Biewener of Harvard University, USA, turned to the peach-faced lovebird (Agapornis roseicollis) – a small parrot-like bird native to the deserts and shrublands of southwestern Africa, but also a popular pet – to see what the birds are doing when landing on a moving target.

After the laborious task of training four lovebirds to fly through a corridor and land on a swinging perch, Bhagavatula and Biewener recorded 100 flights from each bird using two high-speed video cameras (filming at 200 frames s⁻¹), and another video camera (60 frames s⁻¹) mounted on the perch. After looking at 400 flights, they found that, just like a trapeze artist, the small parrots preferred to land on the moving perch at the top of its swing. As the perch reaches this part of the swing, it slows down, which could help the lovebirds grip the perch better. Also, the birds seemed to prefer to land on the swinging perch when it was moving in the same direction as they were flying rather than when the perch was coming towards them. When the researchers tested why this might happen, they found that if the birds landed on the perch as it was moving towards them, the force the birds applied to the swinging perch was nearly twice as high as when they landed on a perch that was moving away from them. ‘If they land when the perch and bird are moving in the same direction, then they face less force upon impact, which is naturally more convenient for the bird’, explains Bhagavatula. While the scientists now knew that the lovebirds preferred to land when their trapeze-like perch was near its apex, they still weren't sure what the birds were doing as they landed to keep their balance.

Because the trapeze sensed how much force the lovebirds landed with and any twisting motion they caused, the researchers discovered that the birds were applying much more force to the trapeze horizontally rather than vertically. This suggests that the birds were approaching the perch from the side rather than dropping down onto it from the top. But the question remained, how are they managing to keep themselves from tumbling off the trapeze if they sometimes land with so much force?

When Bhagavatula and Biewener looked back at the videos, they found that the lovebirds were doing some things that might make their impact on the trapeze less forceful. First, they approached the trapeze at a horizontal angle, rather than approaching from the top. Each bird also pitched their body backwards to ∼82 deg every time they landed, allowing their feet to go out in front of them while using their final wing strokes to slow themselves down prior to landing. Finally, they bent their legs at the ankles and knees to absorb some of the impact. While this may not be exactly how a human would go from one trapeze to another, these acrobatic lovebirds certainly look at ease while landing on a flying trapeze.