A moth or a butterfly, dedicated to the god of War - Pegasus reference, and Leander has been a warrior/rogue fighter almost all his life.
Born in tropical March to April, the first of your kind - Leander ages in Birdsong.
Argent dirt, and odd-colored spectacle - Leander has brown/dirty points, and has spectacle like markings over his eyes.
Allegiant, adroit, docile, guileful - All of these traits match Leander well.
The gentle waters hold you dear - Reference to the sea that borders most of the Throat.
Watch the stars and see yourself running with them. - A possible flying reference?