How do you suppose something like this is made?

Pin cushions stuffed with steel wool are firm like this.

It looks like she’s removed the instructions from the website.

I did find her book here

I’ll keep digging, see what I can come up with

Bam! The book preview on Amazon shows enough of the inside to answer the question.

The body is made of high quality quilting cotton (so, woven, no stretch), and she uses wool stuffing. She does appear to take good care in patterning with regard to the grain, so the bird can best hold its shape.

The preview is actually enough to get a pretty decent tutorial. I suggest taking a look at it!

The wings and tail look like what I did when I made my four-year-old son a lion costume for Halloween. You can stuff something pretty firmly with cotton. I think it would be practically impossible to fit a contoured fabric body around a solid form. You’d probably have to stitch the final seams from the outside.

Or, I suppose, glue it on.

At three my son wanted to be cute, and I made him a bunny rabbit costume. At that point I hadn’t solved the ear problem, so they flopped a lot. By four he wanted to be scary. Of course he didn’t know that was twice as cute.

For the lion’s ears I stitched a narrow channel around the edges of the pointed ears and then packed it snugly with cotton batting, using a thick crochet needle to tamp it in. They held their shape and stood up well. Stuffing them right down to the attaching seam was important so they wouldn’t flop over.