For reasons I can't find, the term "great speckled bird" was historically used in Christian metaphor to represent the Christian church on earth, conceived as the "bride" of Christ.

The complete song goes:

The Great Speckled Bird
                Written by Reverend Guy Smith

                What a beautiful thought I am thinking
                Concerning a great speckled bird
                Remember her name is recorded
                On the pages of God's Holy Word

                Desiring to lower her standards
                They watch every move that she makes
                They long to find fault with her teachings
                But really they find no mistake

                I am glad I have learned of her meekness
                I am proud that my name is in the book
                For I want to be one never fearing
                On the face of my Savior to look

                When He cometh descending from heaven
                On the clouds, as He writes in His Word
                I'll be joyfully carried to meet Him
                On the wings of the great speckled bird

                © Universal Dutchess Music Corp. (BMI)