To seal the overlaps, an aluminum adhesive tape is used.
This Frog Support has been stuck in position with double sided adhesive tape for demonstration purposes only.
Turn the bird over, then seal and secure the joint of the tail sleeve using adhesive tape.
Actually, you probably do something similar every Christmas, but this time you're going to cut off the extra bits and make a sturdier bond between the seams with fabric than you'd get with adhesive tape and paper.
Spread a bead of adhesive around the perimeter of the first panel about one inch away from the adhesive tape that comes already on the panel.