Tides    Maine has some of the highest tides in the world. Tides are critical to certain birding opportunities, especially for shorebirds. For tide chart information, visit Maine Boats.    At high tide, shorebirds go to roost. As tides fall, the birds flock to "first mud" and begin feeding voraciously. Often, this is when they are most concentrated for viewing (and most vulnerable to disturbance!) As tides continue to fall, the peeps disperse across the wide mud flats. Viewing becomes more distant and difficult. The rising tide pushes the birds back to "last mud" and the cycle repeats.    Tide also matters on puffin trips to Machias Seal Island. It is easier to land visitors at high tide, and the captains time their visits during this period. Thus, the departure time differs every day.    Some sites where tide matters:    The best time to see concentrated shorebirds at South Lubec Sand Flats in Downeast Maine is about 2-3 hours before and after high tide.    In Mid-Coast while winter birding, Reid State Park is better at high tide and Popham Beach State Park is better at low. The water depth drops rapidly at Reid, so the variation in exposed beach is relatively small. This brings the sea ducks close to shore. At Popham, the beach is shallow and the exposed area is beach is huge at low tide. Besides making it better for shorebirds, the wide expanse also entices Snow Buntings, Horned Larks, and Lapland Longspurs in autumn.    At Weskeag Marsh, also in Mid-Coast, shorebirds and waders concentrate at high tide. As tides fall, many shorebirds head over to Thomaston to forage in the mudflats adjacent to the boat yard.     In Scarborough Marsh near Portland, high tide often pushes the sharp-tailed sparrows into closer view. As tide falls, wading birds and shorebirds move onto the salt pannes visible from the bike/pedestrian path. At about three hours before and after high tide, nearby Pine Point reaches the optimal level for good shorebirding in August and September.    All along the coast in winter, Purple Sandpipers roost at high tide, gathered closely in tight flocks just above the splashing surf. At low tide, they forage in the seaweed next to the water and can be hard to pick out.     Mergansers and goldeneyes ride the tide as it oscillates in the tidal zone of Maine's biggest rivers. The Kennebec River in Bath and the Penobscot River in Bangor enjoy large tidal changes. The best time to look for Barrow's Goldeneyes in Belfast Harbor is at low tide.