Acorns fall from oak trees, plinking off the roofs of houses and sheds, plunking onto dry ground and crunching underfoot during hikes. Flocks of swallows fly to winter homes, making their way south with other September air travelers. Cicadas hum and strum in the evening air, distinctly cooler now and laced with wisps of fog. Waves lap at a broad, sandy shoreline nourished by the littoral drifts of summer, gently urging Islanders to store up swims like a squirrel stores nuts for winter.