In a major advance in understanding how human eyesight works, scientists have shown that the birds’ amazing flight and landing precision relies on their ability to detect edges.

The research suggests that edge detection is crucial in helping all animals, including humans, move around safely, and may be more important than our ability to see colour.

An international team, led by Indian-origin Partha Bhagavatula and Mandyam Srinivasan of Queensland University, found that budgerigars ignore colour and look for the edge of an object in order to ensure a smooth landing.

“Although a lot is known about the visual cues that help birds navigate when flying over long distances, this is the first study to reveal how budgies navigate from moment to moment and choose where they land.

“It makes sense that birds use contrasting edges to target their landing -- the edge of an object normally presents a good place to get a strong grip and it can help birds to avoid over or undershooting,” said Bhagavatula.

The findings, published in the ‘PLoS ONE’ journal, will help in understanding how birds fly and land so accurately, particularly in dense spaces and low light, and also provide insight into human vision.

“Our results reflect studies on edge detection in bees and primates and suggest that edge detection is critical to helping all animals, including humans, move around. Colour vision is important when it comes to recognising objects, but these findings suggest you don’t need it in order to do many day to day tasks,” said Srinivasan.

The findings also suggest that edge detection may be the key to creating unmanned aerial vehicles and flying robots that can dodge objects while travelling through cluttered environments, a feature that is in high demand, he said.

In order to test the visual features that guide budgies landing, Bhagavatula and a team placed a feeder tray in the middle of a disc on a background of blue paper.

Even though the food was in the centre of the disc, the birds landed on the edge and then walked to the middle. .

“This showed that they were using the contrasting edge of the disc to guide a safe landing, instead of just setting down close to the food,” said Bhagavatula.

“Birds can see in all three of the human primary colours -- red, blue and green -- and also ultraviolet, but their edge detection skills appear to be colour-blind,” he said.