Eri posted a DIY tutorial for this amazing bird wings costume on her blog, Llevo el Invierno. She provides a free pattern that you can download as well, sized for children ages 18 to 36 months.
Using the template she provides, you can assemble the wings by either gluing or sewing the fabric.
According to Eri, the project isn’t all that difficult. It just takes some time and patience to cut and paste/sew all the pieces of fabric.
Isn’t her daughter Emma absolutely adorable?