This is an apt description, Biblically - and Lyrically for the song, of the Word of God (referring to the meaning in the original manuscripts), and those who know that it is the work of The Holy Spirit to guide the believers in that which Christ has provided through the Cross and His Resurrection, into becoming a consecrated people known as The Church. The two become One as The Living Word becomes alive in applying scriptures to daily living circumstances and that is the work of The Holy Spirit.And this is the Christian's work of living the Christian life, ie., believing and applyhing the Gospel of Jesus Christ rather than a gospel of tradition or written by man and depending upon The Holy Spirit to accomplish this goal within himself/herself,the believer, who also knows that he/she cannot be righteous in and of themselves. The Bible is explicit in explaining that Holy Men of God have written the words that the Holy Spirit has given them to record; thus the canonizing of that which is known as The Holy Bible and the truest recording of those olden scriptures are given by the Authorized Kings James Version (in my opinion). So to answer the question: it seems correct to think that this Speckled Bird reference is supposed to represent both The Holy Bible and those who follow the teachings of the Gospel of Jesus Christ - those who can be considered "True Christians" or true followers of The Lord Jesus Christ.
Another Biblical prophetic description of a true Christian comes to my mind: "Straight is the gate and narrow is the way which ledeth unto life and few there be who find it" (compared to the greater number whose gate is opened as wide as their way to whom Christ will someday say, "Go your way for I never knew you".