Humanoid bird
Described as a humanoid bird, this creature was encountered in 2254 by Captain Christopher Pike while in captivity on Talos IV. ()

Another individual of this species was encountered thirteen years later, in 2267, by a landing party of the , albeit dead, stuffed and on display in Trelane's mansion. It was later destroyed by Trelane with a phaser. ()

Background information 

In the script of "The Cage", this creature was described as "an incredibly thin humanoid-bird creature" with "leathery wing[s]".

The humanoid bird was played by Janos Prohaska (who also played the anthropoid ape in the same episode). The costume was a creation by master sculptor Wah Chang for "The Cage" and tailor-made for Prohaska. The costume was shortly thereafter used as the Megasoid in the second season episode "The Duplicate Man" of the television series , for which Prohaska and Chang also worked. () Incidentally, the head appliance resembled an earlier Chang creation, that of the Empyrian featured in the earlier episode "Second Chance". 

Originally, the scene with the humanoid bird for "The Cage" was to have been far more extended, as its director Robert Butler recalled. "I remember there was some chicken – some killer fowl – being locked in some cell somewhere, and I'm talking to this stuntman – it's crazy, me talking to this Janos Prohaska, [who was] Hungarian or something...[saying], 'Janos, okay that's good, baby, now try this.' And there's this big chicken – this killer chicken – or some equivalent. I mean, it was nuts." (These Are the Voyages: TOS Season One, 1st ed, p. 60) Needless to say, the extended scenes were not utilized in the pilot as presented.

That the specimen encountered in "The Squire of Gothos" was indeed a re-use of the costume used in "The Cage" was confirmed in the reference book The Outer Limits Companion (1999), where it was described that it was composed of the original costume and make-up appliances. 

Avians