Loons & Grebes
The loons (Gaviidae) and grebes (Podicipedidae) are most often seen during the colder months on Stellwagen Bank. Their yearly movements could be summed up as a migration from east to west: as the birds leave their breeding grounds of ponds and lakes to marine habitats along the coast. Often floating low in the water, they dive down to capture fish using good eyesight, long, flexible necks and pointed bill. None of these birds are very common on the Bank and are usually found closer to shore while heading out for research cruises and whale-watches. In flight, their long necks hang low and their large, paddle shaped feet are carried well beyond the tail, creating a very distinctive silhouette.
The common loon, Gavia immer is a large (up to 3 feet or 1 meter wing span) aquatic bird that breeds on northern lakes and winters along the Atlantic coast. On Stellwagen they are found in their non breeding plumage, a speckled black and white, between October and May. The common loon is predominantly a fish eating bird, diving from a
floating position to catch prey beneath the surface with a long, dagger like bill. Loons are awkward on land because their legs are best designed for swimming: broad paddles set far back on the body. These big feet trailing behind give them a distinctive silhouette in flight. The yodeling cry of this bird is rarely, but sometimes heard on migration.
The red-throated loon, Gavia stellata breeds in the high arctic of Eurasia, Alaska, Canada and Greenland, making them the most widely distributed loon. Its occurrence, as a migrant, on Stellwagen Bank is similar to the common loon, but in appearance the red-throated is smaller, and pale gray with a slightly upturned bill. This loon may fly in large continuous flocks during migration. Like the common, they are expert divers and have been found in fishing gear 60 meters (200 feet) below the surface.
Both the horned grebe, Podiceps auritus and the red-necked grebe, Podiceps grisegena have a Holarctic breeding distribution: nesting on fresh water lakes and ponds, then migrating south to winter along salt water shorelines especially along the coast or on protected bays. They often fly during moonlight nights or swim during the day while on migration. The red-necked grebe is more likely to be observed on Stellwagen, most likely in late winter (March). Grebes are small moonlike, diving birds, typically gray above and white below when observed here in the wintering grounds. They are arguably the best adapted birds to an aquatic existence: their lobed feet are set well back on their bodies for powerful swimming and diving; they can hold their breath for up to three minutes and are remarkably water-proof. Wads of their exquisite body feathers are commonly found in their stomachs, a behavior unique to grebes and poorly understood. Neither are common on Stellwagen Bank and are more likely to be found outside of harbors while on the way to the Bank.