Unfortunately, it can't. The xulrunner that the Songbird team uses is heavily patched and is required for Songbird to run properly. I've been back and forth with the developers about this multiple times. They're trying upstream as many as the changes as possible, but it is still required. You can follow the Fedora review process over at:

https://bugzilla.redhat.com/show_bug.cgi?id=453422