I'm a huge Tom Rush fan too. I don't think of him as a song-writer, but as a performer. I realize that he has written some songs, but his strength is in his interpretations of other people's songs, like joanie Mitchell's Urge For Going or David Whiffen's Driving Wheel.
I've heard criticisms of Tom for being a "Cover Artist", but I've suffered through many evenings of singer/songwriters who refuse to perform the works of others, but perform only their own so-so songs. If a songwriter is truly gifted, like Fred Eaglesmith or Todd Snider or Bob Snider, then they can put on a great show using only their own material, but most singer/songwriters don't have this talent. Many of my favourites, like Pete Seeger, Billie Holiday, Jack Elliott... are better known for their performance of others songs and traditional songs, though they did write songs themselves.
I have written songs and tunes , but am not prolific enough to put on a whole performance of just my own tunes and songs. I have had two of my songs recorded by others and I find it a great honour. I'd like to extend that feeling to others by performing (and crediting) their songs. I always mention the writer in my introduction or liner notes.