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In issue 309 -
When an Older Parrot Has Never Learned Skilful Flight – Complete Psittacine by Eb Cravens
In issue 309 -
Scarlet Macaws – were they really bred by indigenous people in the 12th century? Rosemary Low asks the question
In issue 309 -
Understanding the link between nutrition, hormonal behaviours and the avian endocrine system, Part 1 – The Holistic Parrot by Leslie Moran
In issue 309 -
The Yellow-eared Parrot – continues to expand its range in Colombia. By David Waugh, Correspondent, Loro Parque Fundación
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 The October 2023 edition of Parrots magazine (issue 309) will be available to download from 13th September via a link which will be emailed to subscribers. Single copies will be available from our online shop. You can save money by subscribing – find out more here.

Parrots and a third limb

Spreads for web Parrots 278 4

By Devorah Bennu, PhD, aka “GrrlScientist”

Humans have had an extraordinarily long fascination with the ‘triskelion motif’ whose name is derived from the Greek and translates as “three-legged”. Three-legged creatures feature in ancient Chinese mythology, a triskelion featuring three human legs joined at the hip and flexed at the knees adorns the coat of arms for the Isle of Man, and much more recently, author H.G. Wells described Martian invaders attacking Earth with massive, three-legged war machines called tripods that they modelled after their own three-legged body plan in his extraordinarily popular and influential 1898 science-fiction novel, War of the Worlds.

Despite this excess of imagination, there are no three-legged animals alive today, and nor have any such fossils ever been unearthed. Considering the immense length of geologic time during which life has evolved, and the many riotous forms life has taken, it makes one wonder why a three-legged animal never once appeared.

Studies indicate there is a developmental constraint against an animal possessing an odd number of limbs because the bilaterally symmetrical body plan only gives rise to even numbers of limbs, and this became the established body plan very early in evolutionary history. Thus, tripedalism is known to scientists as a ‘forbidden phenotype’ even though locomotion studies suggest that a three-legged phenotype would be functional and possibly advantageous over some of these other, more familiar, body plans.

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