Study finds parrots use their heads as a “third limb”
The parrots’ beaks first contacted the vertical runway when climbing at a 45-degree angle, and then consistently made contact while climbing at a 90-degree angle. Credit: New York Institute of Technology

There has never been an odd number of limbs in a fish, mammal, bird, reptile, or amphibian. Some animals seem to use other body parts as a third or fifth limb to move from one place to another.

While parrots can't use their wings for grasping, they climb by extending their heads and grasping branches or other surfaces with their beaks. It is not clear if the head is used for stabilization or if it is just used for support. Many studies have highlighted parrots' intelligence, but little research has been done on their behavior.

For the first time, research shows that parrots use their head as a third limb. A new study in the journal Proceedings of the Royal Society B was written by a medical student and an assistant professor.

The parrots climbed a man-made runway that was positioned at angles ranging from zero to 90 degrees. Two high-speed cameras captured their movement, while a small force plate mounted to the back of the runway measured the force generated by the beak, hindlimbs, and tail as each body part came into contact with the runway.

The parrots first contacted the runway when climbing at a 45 degree angle and then at a 90 degree angle. The forces produced by the beaks of the parrots were of equal or greater magnitudes than those produced by the limbs of humans. The tails of the birds produced minimal forces, suggesting that the tail is used for support and not as an additional limb.

Credit: Melody Young and Michael Granatosky

Young, who is in NYITCOM's Osteopathic Medicine, D.O./Medical and Biological Sciences, says that parrots have evolved over time to support their climbing behaviors.

Although many birds climb vertically, parrots are the only birds known to engage the head as a third limb. She said that this behavior seems to have necessitated changes to the body's muscles, including neck flexors that generate additional force.

An expert in the evolution of animal movement suggests that parrots may be different from other animals.

While juvenile pandas are known to swing their heads as they ascend vertical surfaces, they do not make contact with the surface. The head as a propulsive limb is an evolutionary novelty that has only ever existed in parrots.

The first step in the series of studies is the project. There are many parallels between parrots and living primates. Over the next few years, Granatosky and his lab will work to understand the biology of parrots and develop bio-inspired robotic systems that mimic this movement.

More information: Melody W. Young et al, Overcoming a 'forbidden phenotype': the parrot's head supports, propels and powers tripedal locomotion, Proceedings of the Royal Society B: Biological Sciences (2022). DOI: 10.1098/rspb.2022.0245 Journal information: Proceedings of the Royal Society B Citation: Study finds parrots use their heads as a 'third limb' (2022, May 19) retrieved 19 May 2022 from This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.