Of the two, much more is known about Earth-Two's Skylark as opposed to Earth-One's Vulture-Man. Originally S.K. Lark, a man convicted of treason against the U.S. prohibited from setting foot again on American soil, he uses his knowledge of gliders and and aviation to become the Skylark. Vulture-Man's goal wasn't vengeance but greed, nevertheless his methods were similar.
While Skylark faced Green Arrow and Speedy twice, at the end of the second encounter there was a promise of more such confrontations that heretofore have been left unpublished, Vulture-Man was evidently a one-hit wonder. And that hit he felt when facing the Battling Bowmen clipped his wings for good!