He says the design has been slightly refined over the years:
You might want to note that it finally succumbed to the elements after about 2-1/2 years. Also it's very windy in my backyard and I kept losing the cap off the top, so I cut the top off a 1-1/2 litre mineral-water bottle just below the neck and slipped that over the top to keep the rain out.
I like it a lot. Of course, it's not exactly a thing of beauty. But I don't put out birdfeeders to adorn the garden. I put them out to attract the birds, which are more beautiful than any garden ornament.