It seems that the "calling" birds of the Fourth Day of Christmas were originally "colly" birds. Colly, meaning black, is derived from the Old World word for coal. When stitched on 16ct fabric, this design will fit a 5"w x 3"h card window. To make a Christmas card, an accessory pack containing trifold card with envelope, "window glass," printed insertable greeting page, and assembly instructions is available for purchase. Contact designer at ljjstitcher@verizon.net