Or you could do what I did and use a scrap of stainless steel hardware
cloth from McMaster-Carr, shaped to the boom end and held on with gorilla tape. Decidedly low-tech, but the starlings have never returned.
Just sayin', for the benefit of other DIY'ers... though it is indeed a bit less finished looking!
Cheers and good luck with the product... I was quite amazed at how quickly a family
of starlings colonized my boom (and made a royal mess of the cockpit). Nothing like having a marina neighbor call and say "you better get down here right away" to get the heart pounding; I was relieved when it was only birds!