Lovebirds, small parrots with vibrant rainbow plumage and cheeky personalities, are popular pets. They swing from ropes, hug their peers, and compete for treats waddling with all the urgency of toddlers seeing a cookie. But, along with other parrots, they also do something strange: they use their faces to climb walls.
Give these birds a vertical surface to climb on, and they will alternate between left leg, right leg, and beak as if their mouths were another limb. In fact, a new analysis of the forces exerted by the lovebirds reveals that this is precisely what they are doing. Somehow, a team of scientists wrote in the journal Proceedings of the Royal Society B on Wednesday, birds and perhaps other parrot species have reused the muscles in their necks and heads so they can walk on their beaks, using them in the same way. way climbers do. your arms
Climbing with a beak as a third limb is peculiar because third limbs are generally not something life on Earth is capable of producing, said Michael Granatosky, an assistant professor of anatomy at the New York Institute of Technology and an author of the new paper.
The fascinating world of birds
“There is this very deep aspect of our biology that everything is two-sided” in much of the animal kingdom, he said. The situation makes it unlikely that he will grow an odd number of walking limbs.
Some animals have developed alternative solutions. Kangaroos use their tails as a fifth limb when hopping slowly, pushing themselves off the ground with their butts the same way they do with their feet.
To see if parrots used their beaks in similar ways, Dr. Granatosky and a graduate student, Melody Young, and their colleagues brought six pink-faced lovebirds from a pet store to the lab. They had the birds climb up a surface that was equipped with a sensor to keep track of how much force they were exerting and in what directions. The scientists found that the propulsive force the birds applied through their beaks was similar to that provided by their legs. What had begun as a way of eating had morphed into a way of walking, with spikes as powerful as their limbs.
“For them, taking their faces and integrating them into their stride cycle is pretty incredible,” said Ms Young, who pointed out that the birds’ nervous systems would have to have changed to adapt bill movement to the rhythm of walking.
Dr. Granatosky speculates that parrots may have developed this ability because, like woodpeckers and nuthatches, they can’t jump up and down tree trunks. Parrots alternate their legs when they walk, rather than propel themselves with both legs at once. So when the challenge of moving vertically came, they had to come up with something different, something that would create the third branch that developmental biology couldn’t provide.
How often parrots do this three-legged walk in their daily lives is another question researchers have. To get an idea of the role it plays in their behavior, Dr. Granatosky has sent students to make detailed observations of the green parakeets that live in the imposing Gothic Revival gate of Green-Wood Cemetery in Brooklyn.
While the results have yet to be published, he hopes the lovebirds and monk parakeets will help shed light on how the parrots developed such an unusual way of climbing and what changes they made to their bodies to do so.