Yesterday while on a regular weekly shorebird survey of Rich Inlet, Tara found Orange Green is still roosting on the shoals there. He was with 43 other oystercatchers using the inlet, 146 Black Skimmers, and assorted other shorebirds. Though he has lost his satellite transmitter, his bands still identify him.
Like Oreo and the oystercatchers that were roosting on the docks in the Intracoastal Waterway, the Rich Inlet flock has gotten over their nesting seasons territoriality and are now looking for other oystercatchers, or even other shorebirds, to roost with. These flocks congregate at inlets along the North Carolina coast during fall migration, which peaks in August and September.
Audubon North Carolina has been conducting shorebird surveys at inlets including Rich Inlet since 2008, and the migrating oystercatchers are reflected in a fall increase in oystercatcher numbers at inlets. Seeing such increases indicates that new individuals are arriving in an area. Numbers drop off again in October and November. That means that the bump in numbers was from individuals that were migrating through the area, using the inlet as a place to stop, rest, and refuel, just as CFX took a pit stop at Masonboro Island on his way to South Carolina.
Inlets are so important to migrating oystercatchers and other shorebirds because they offer both feeding and roosting habitat. Orange Green and the other oystercatchers took advantage of shoals that remain dry at high tide for roosting, and they use the surrounding marsh for feeding, as we’ve seen from Orange Green’s satellite tracks. Meanwhile, other species of shorebirds like Piping Plovers and Short-billed Dowitchers use sandbars and intertidal shoals (shoals that are underwater for part of the tidal cycle) for foraging areas, since they tend to accumulate large numbers of the tiny marine worms and others invertebrates that they specialize on. This means that during migration, natural inlets like Rich that still have large shoals and varied habitat are full of migrating birds.
You may also wonder why spring migration, which takes place in February, March, and April, does not reflect a similar large bump in oystercatcher numbers. One reason may be that in the spring, migrating oystercatchers (as well as all other species of migrants) are in a race to arrive at their nesting areas and secure the best territories first. If they can make the flight in one leap, oystercatchers may choose not to stop so they won’t get behind. But for now, the oystercatchers can afford to move at a more leisurely pace as they wing towards their wintering areas.