The beaks of the parrots were first in contact with the vertical runway at a 45-degree angle, and then sequentially in contact at a 90-degree angle. Credit: New York Institute of Technology

No vertebrates (fish, mammals, birds, reptiles or amphibians) have ever had an odd number of limbs. Despite this “forbidden phenotype,” some animals seem to use other parts of the body as a third or fifth “limb” to move from one place to another.


For example, for now parrots unable to use their wings to capture, they rise by pulling their head out and grabbing their beaks by branches or other surfaces. However, it is unclear whether it will head acts as a “third limbs“which moves the bird, or, if simply used for stabilization, the beak engages the surface for support. In addition, while many studies have highlighted the incredible intelligence of parrots, research on their musculoskeletal behavior is virtually non-existent.

Now, for the first time, a study by the New York College of Technology for Osteopathic Medicine (NYITCOM) has shown that parrots actually use their head as a motor third limb. A new study in the journal Proceedings of the Royal Society BThe authors are medical student Melody Young and Ph.D. Michael Granatoski, an associate professor of anatomy, analyzed the climbing gaits of pink-eared agapornis (Agapornis roseicollis), a species of small parrots.

The researchers developed a series of experiments in which parrots climbed an artificial vertical runway at angles from zero to 90 degrees. Two high speed cameras recorded their movement, while a small force plate mounted on the back of the runway measured the force generated by the beak, hind limbs and tail when each part of the body was in contact with the runway.

The beaks of parrots first came into contact with the runway when lifted at an angle of 45 degrees, and when lifted at an angle of 90 degrees created forces comparable to those created by the hind limbs. In fact, the forces created by parrot beaks were equal to or greater than the forces known to be created by human limbs or other large primates during climbing. On the contrary, bird tails created minimal strength, suggesting that the tail is used simply for support rather than as an additional limb.

Credit: Melody Young and Michael Granatosky

Young, who is studying Osteopathic Medicine at NYITCOM, DO / Medical & Biological Sciences, Ph.D. The program notes that the anatomy of parrots has probably evolved over the years to support this resourceful climbing behavior.

“Although many birds rise vertically, so far parrots are the only birds that are known to engage the head as a third limb. This behavior seems to have necessitated neuromuscular changes over time, including the neck flexors that create additional strength and modifications of spinal nerve circuits, ”she said.

Granatoski, an expert in the evolution of animal movement (movement), believes that innovative climbing parrots behavior can also distinguish them from other animals.

“Although juvenile pandas are known to wave their heads to the side while climbing vertical surfaces, they seem to use their head as a“ fifth limb, ”it does not come into contact with the surface. The use of the head as a moving limb is an evolutionary novelty that, “As far as we know, existed only in parrots,” said Granatoski. “We hope our findings will improve our understanding of how animals co-opt unusual anatomical structures to adopt entirely new behaviors.”

This project is the first step in a series of studies on the locomotor behavior of parrots. Parrots are an ancient tree (tree) line that has many behavioral and anatomical parallels with living primates. Over the next few years, Granatoski and his lab will work to understand the anatomical and neuromuscular underpinnings of parrots ’unusual musculoskeletal behavior, to develop bio-inspired robotic systems that simulate this movement.


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Additional information:
Melody W. Young et al., Overcoming the “forbidden phenotype”: the parrot’s head supports, moves and provides movement on three legs, Proceedings of the Royal Society B: Biological Sciences (2022). DOI: 10.1098 / rspb.2022.0245

Citation: Research shows that parrots use the head as a “third limb” (2022, May 19), obtained May 19, 2022 from https://phys.org/news/2022-05-parrots-limb.html

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