Wild Side : On the wing
Much of the ecological value of the Vineyard stems from what lives here permanently: rare or highly adapted plants and animals associated with our unusual habitats. But don't overlook how important the Island is to transient animals - the birds, bats, fish, insects, and others that pause here while migrating to rest and refuel. Migration works as a lifestyle because it allows animals to exploit seasonally abundant resources while avoiding difficult conditions. But long-distance travel requires immense energy, and without productive stopping points on the way, migrants can fall fatally short of their destination. Our rich natural resources help sustain wildlife on a hemispheric scale.
August is the peak month for observing one of the most interesting groups of species that visit the Island: sandpipers, plovers, and related wading birds known collectively as shorebirds. With more than a dozen families and more than 200 species worldwide, the shorebirds are a diverse and successful group; while some of these species don't migrate or (like our beach-nesting piping plovers) travel relatively short distances, the group as a whole is highly mobile. Some of the species that pass through the Vineyard rank among the most impressive avian travelers - swift, direct, and seemingly effortless fliers, carried vast distances by their pointed wings.
The white-rumped sandpiper, for example, is a mud-brown, eight-inch visitor to our pond edges and mudflats (the ponds in the salt marsh near Bend in the Road Beach attract this species quite reliably, though white-rumps can be hard to distinguish from several similar species that also occur there). Like all of our migrant sandpipers, they spend most of their time here feeding frenetically, picking small invertebrates out of shallow water or mud. (On nocturnal beach visits, I've found that some species continue feeding even at night; their sensitive beak tips detect prey readily even in the dark.)
There is good reason for this activity: all these birds have a journey ahead of them, and in the case of the white-rumped sandpiper, the route leads from breeding grounds on the northernmost fringe of North America to wintering grounds near the southern end of South America. Much of this journey takes place in marathon flights over thousands of miles of open water. One wants to be fully fueled before taking off! Viewing one of these unimposing birds, it is hard to believe the distances and differences in habitat they traverse.
This column is too brief to address the complexities (there are many) of shorebird identification; even veteran birders struggle to distinguish some species. And their wary natures and penchant for open, often muddy habitats make most shorebirds hard to approach closely. On the other hand, shorebirds spend much of their time in the open, making their behavior easy to observe. Given the wide range of size, leg length, and bill length, it's no surprise to find that the feeding behavior varies widely from species to species. Stout-billed and relatively short-legged, plovers pick prey from the mud's surface and even round up grasshoppers in mown hay fields. At the other extreme, dowitchers and godwits (noble birds, regrettably rare here) probe deeply in the mud.
Relative to some other sites on the Massachusetts coast, the Vineyard is not a major stopover site for shorebirds (the beaches and flats around Chatham and the marshes and mud flats of the Newburyport/Plum Island area attract many more birds). But the numbers visiting the Island are significant, and seem to be increasing in the case of some species. The last decade or so, for example, has seen the short-billed dowitcher go from being a good find even in small numbers to a regular and fairly plentiful visitor.
Growth of population may cause some such changes (most shorebird species are still recovering from indiscriminate, industrial-scale market hunting practiced into the early years of the 20th century). But improving habitat may also figure: in Katama Bay, especially, sediment deposition has expanded the mud flats even as the Norton Point breach has improved water quality. Tidal flats near the openings of the great ponds, Red Beach on Menemsha Pond, agricultural fields at Katama Farm, and the flats exposed near Sarson's Island, in Sengekontacket Pond, at low tide are other prime spots for finding shorebirds.
I'm certainly fond of our breeding shorebirds: the piping plovers, oystercatchers, killdeer, and willets that are here all summer. But I have special feelings for the more migratory shorebirds, with their specialized anatomies, interesting behavior, and powerful flight. They seem to epitomize all that is admirable about birds, and their annual late summer passage is a high point of the year for me. Birding skills help but are not necessary to appreciate these visitors; binoculars, alert eyes, and a visit to nearly any beach, marsh, mud flat, or mown or plowed field will let you share their epic journey.