Hadn't been a problem yet (and I've now owned this boat 6 years) but that thought entered my mind too when we saw an osprey take off from our upper spreaders last week. Judging by the amount of droppings on deck it was apparent (she or) he had been hanging out there, and I'm glad to see that the flash tape seems to be an effective repellent.

I have also bought plastic spike strips that I plan to tape and tie-wrap to the spreaders soon.