My fave version of this great song -Emmylou notwithstanding - is by the Original Flatlanders trio
Never was much of a Jimmy Dale fan, but Butch just kills it on, well not this specific recording, but one that I used to hear real often that I can't seem to find very readily
Special place in my heart for that song. When my oldest daughter (now almost 21) was a little baby and was having a really hard time she was crying inconsolably. The only thing I could think to do was to sing her that song. I held her and kept singing it to her over and over for about two hours until she finally settled down. It has been a really special song to both of us ever since that day. She recently (twenty years later) made me a leather wallet with "If You Were A Bluebird" stamped on it.
Coincidentally, Joe Ely is about to release an album of songs he wrote for his daughter when she was a baby. It's called Flatland Lullaby. Here's a link: http://www.ely.com/new-page
... for me, this has long been a much-loved song, so much so that I recorded it years ago.
I guess you probably don't need to listen to my recording if you already love Joe Ely's version, or Emmylou's, but if you feel that you have to hear every version out there of this sweet song, then I humbly offer up mine too...