Birds of Casco Bay with Seacoast Tours August 2025 Trip Report.

Now in its 5^th year, our “Birds of Casco Bay” tour with our partners Seacoast Tours of Freeport once again headed out on an August itinerary focused on shorebirds. It sure was a beautiful day for it, and shorebirds put on a show!

Leaving the Harraseeket River and rounding Mosiers Island, we began to slowly work up the Royal River. With the approaching low tide, the mudflats were extensive and full of shorebirds. With the narrow channel, birds were often quite close to the boat, comfortably feeding at the water’s edge as we slowly motored by. We compared Greater and Lesser Yellowlegs side-by-side and sorted through the masses of Semipalmated Sandpipers to find dozens of Least Sandpipers.

Common Terns were often feeding around us. Snowy Egrets (20+) joined Great Blue Herons (10+) on the mudflats and river edges, with others seen elsewhere around the bay, while a scattered few Laughing Gulls joined the more abundant Herring, Ring-billed, and Great Black-backed Gulls. We went up the river as far as the Lower Falls Landing, then turned around and studied shorebirds as we drifted back down the river. In the end, our shorebird tallies were respectable, with an estimated 1200 Semipalmated Sandpipers, a goodly 66 Lesser Yellowlegs, 50 Semipalmated Plovers, 40 Least Sandpipers, 9 Greater Yellowlegs, and 3 White-rumped Sandpipers.

 An adult Bald Eagle (one of the 5 we saw today) greeted us as we entered the Royal River and was still standing guard as we departed.

We then motored over to the Upper Green Islands. There, we saw more Ospreys (at least 20 in total throughout the trip today!), lots of Common Eiders and Double-crested Cormorants of all ages, and most excitingly, 3 American Oystercatchers!

We first found oystercatchers out here on a tour together in 2022 and confirmed that they were in fact breeding when we found a flightless chick in 2023. This year, the smudgy-tipped bill on one of the birds (out of view in the photo at the top of the page) is indicative of another successful fledging. Who would have thought this tiny island and ledge could support one of only a dozen or so pairs in the entire state?

Someone asked what they were feeding on, especially given the lack of wild oysters here, and one bird obligingly answered the question for us, showing off a mussel it had just pulled from the intertidal zone.

We also said hello to some Harbor Seals, of course…

…And then checked out Osprey nests here and at French Island, where we studied the speckled plumage of fresh juveniles.

More Ospreys, Common Terns, and Common Eiders among others were noted as we made the trip upriver to the dock, bringing another successful tour to a close. But don’t worry, Seacoast Tours and I are back at it in October, with our waterfowl-focused edition of Birds of Casco Bay!