From songfacts.com (an anthology of news magazine feature articles; not footnoted though) :
“In Philip Norman’s book Sir Elton: The Definitive Biography, this early Elton John/Bernie Taupin composition is described as “the wistful song of a captive bird turned loose by a prisoner.” Taupin himself describes it as a good song with a “fairly naïve lyric.”
“Skyline Pigeon” sounds as though it may have been inspired by the 1962 film “Birdman of Alcatraz”, which is a sanitized biopic of double killer Robert Stroud. Elton recorded the song for his debut album “Empty Sky”, through which the theme of imprisonment – unjust or otherwise – runs. It was first released in August 1968 though, by Roger Cook, and later that same month by Guy Darrell. Darrell had a minor hit in 1973 with “I’ve Been Hurt,” but never lived up to the hype…
“When Elton first recorded it, he used a harpsichord, and in the style of the album the song was light on production, but in 1973 it was re-released as the B-Side of “Daniel” with a full arrangement. It was also recorded by Geoff Long, a blind musician and occasional songwriter from Sydenham, London for his 2004 CD “After the Party”.
“On April 11, 1990, Elton played this at the funeral for the 18-year-old AIDS victim Ryan White, whom he had befriended. Elton was one of the pallbearers.”