I think it is more probable at this time of year, that you appeared to be a threat to the birds mating territory more than food. I've flown with hawks, eagles, falcons and other birds of prey for years (read that decades) without incident, they are great indicators of lift. I currently fly in bald eagle and redtail territory and have both BE and redtail nests on my property. Would the color scheme of your sailplane be anywhere close to a birds coloring?