Hosios David, Thessaloniki. 5th C church and mosaic, 12th C frescoes. The theophany - apocalyptic appearance of the Lord - is really unusual. I love the beardless Jesus, when he shows up. There are a number of miracle legends associated with the mosaic. My favorite is that in the late days of Iconoclasm, an Egyptian monk was praying in the monastery when with a great shake of the earth, the mosaic appeared! He took it as a validation of icons and as a representation of the Real Jesus. I teach this one all the time.
Shown is a 6th century mosaic found in Madaba, Jordan. Here I will provide 3, quick lines of thought in relation to such depictions, largely following the scholarship of art historian Kristin Aavitsland (2012).
One symbolic meaning for the birdcage iconographic imagery comes from the classical world, where the bird may be viewed as a metaphor for the human soul. Neo-Platonists and Stoics (such as Porphyry, Seneca) paralleled the birdcage to human life on earth: the soul (like the bird) yearns for its freedom, wishing to return to its heavenly origin (this is achieved by death). The soul is confined within the body, like a bird in a cage.
We occasionally see a similar use of the image of the caged bird in the Jewish tradition. The interpretation of this differs, here it can given a more positive meaning: the cage being viewed as protection rather than a confining prison. The secure cage protects those inside from the dangers of the outside world. Thus, the bird within the cage can here be viewed as a metaphor for the chosen people of God, who are proceeded by the Lord.
Alluding to both classical and Jewish texts, a similar image is again found in the Judaeo-Christian tradition. For example: “We have escaped like a bird from the fowler’s snare; the snare has been broken, and we have escaped” (Psalm 124). Here the image is used as a metaphor for deliverance, and the completeness of this deliverance is portrayed not only by merely escaping, but in that the danger itself is destroyed (the snare is broken).