Visitors stopping by Middle Creek Wildlife Management Area this week found yet another post-breeding wanderer feeding in the shallows of the main lake and adjacent pond along Hopeland Road—a juvenile Little Blue Heron.
The juvenile Little Blue Heron is a white bird resembling an egret during its first year. At about one year of age, it begins molt into a deep blue adult plumage. Young birds are notorious for roaming inland and north from breeding areas along the Atlantic coast and throughout the south. They are a post-breeding wanderer nowhere near as rare as the Limpkin seen at Middle Creek a week ago; a few are found each summer in the Lower Susquehanna River Watershed.
A juvenile Little Blue Heron currently at Middle Creek Wildlife Management Area. Note the yellow legs and pale beak, field marks that help separate this species from the Great Egret and Snowy Egret.
As oft times happens, birders attracted to see one unusual bird find another in the vicinity. So with fall shorebird migration ramping up, the discovery of something out of the ordinary isn’t a total surprise, particularly where habitat is good and people are watching.
A Hudsonian Godwit (Limosa haemastica) has arrived on mudflats at Middle Creek Wildlife Management Area.
The arrival of a Hudsonian Godwit is not an unheard of occurrence in the lower Susquehanna region, but locating one that sticks around and provides abundant viewing opportunities is a rarity. This adult presumably left the species’ breeding areas in Alaska or central/western Canada in recent weeks to begin its southbound movement. Hudsonian Godwits pass through the eastern United States only during the autumn migration, and the majority fly by without being noticed along a route that mostly takes them offshore of the Mid-Atlantic States.
The Hudsonian Godwit (right) at Middle Creek W.M.A. feeding with other migrating shorebirds…a Lesser Yellowlegs (top) and a Least Sandpiper (left).To probe the muddy bottom for invertebrates, Hudsonian Godwits will often wade in deeper water than accompanying species.This godwit seemed to be capturing small snails, presumably the young of the thousands of adult Acute Bladder Snails (Physellla acuta) seen here covering the surface of the mud. This species of air-breathing freshwater snail is tolerant of low levels of dissolved oxygen and is frequently the only mollusk found in polluted waters of the lower Susquehanna valley.For feeding shorebirds, the young snails may be more edible than the adults due to their fragile shells. Small birds like the Least Sandpiper may also be consuming the gelatinous egg masses. In North America, the Acute Bladder Snail was believed to be an introduced species from Europe. DNA testing has now determined that it is actually a native species that was instead transported into Europe from North America early in the nineteenth century or before. Locally, the snails were known as Physella heterostropha and were thought to be native. However, the recent genetic tests have shown Physella heterostropha and Physella integra, a snail first described by Lancaster County naturalist Samuel S. Haldeman, to be synonyms of Physella acuta. Click the “Freshwater Snails” tab at the top of this page to learn more about these mollusks.The Hudsonian Godwit at Middle Creek W.M.A., you may never get a better look!
