Birding the Hudson Valley

Lloyd.

The birds of the Hudson Valley live in a place that has been shaped by both nature and humans. Indeed, it is the combination of natural beauty and rich cultural heritage that makes the Hudson Valley unique and sets it apart from the rest of New York State. Though picturesque and scenic, most of the area is no longer natural. Pristine ecosystems have been replaced by a mosaic of altered lands and waters to create a modern natural and cultural landscape.

This chapter explains how glaciers formed the rivers, lakes, cliffs, drumlins, waterfalls, and soils of the Hudson Valley. It briefly explores how the activities of Native Americans and European settlers changed the Hudson River, its shoreline, its forested uplands, and its wildlife. Finally, this chapter describes the present-day landscape of the Hudson Valley, looking first at the river and then at large biophysical regions distinguished by their geology, climate, topography, and soils. This broad overview provides a sense of how the land has changed and sets the stage for understanding the distribution of birds in the Hudson Valley.

A Land Shaped by Glaciers

During the last ice age, the Hudson Valley was covered by glaciers. As the massive ice sheets advanced from north to south, they scoured and scraped the land below, destroying any living organisms in their paths. Glaciers gouged out and deepened the Hudson River channel. They robbed the ocean of water as they advanced, converting liquid water to ice and lowering sea level so much that most of the continental shelf near New York City was actually dry land. The Hudson Canyon, a deep-water gorge in the continental shelf favored by pelagic birds, is part of the river’s now submerged ancient riverbed.

Ice advanced and retreated over the Hudson Valley many times during the Pleistocene Epoch, reaching a thickness of nearly half a mile in some places. As the glaciers passed, the ice ripped off loose masses of bedrock, shaping the escarpments and cliff faces visible today on the west side of the Hudson. Underneath, the ice piles of coarse sediments were left in egg-shaped hills called drumlins, which dot pastoral farmlands throughout the Hudson Valley. The glaciers cut drainage channels to the Hudson River, forming future waterfalls. The great ice sheets bulldozed rocks and boulders ahead of them, and wherever they stopped, they deposited massive ridges of boulders, gravel, silt, and sediment known as glacial moraines.

After the last glacial advance, about twenty-two thousand years ago, the ice sheet began to melt faster than it grew; this resulted in a northward retreat. As it melted, the ice sheet carried sand and silt down its face, leaving a smooth, flat, outwash plain. The slow-moving, melting glaciers formed lakes and wetlands by scooping out areas of soft rock. Chunks of ice broke off and became buried in the sandy outwash. When this ice melted, the water-filled depressions became the valley’s kettle-hole ponds and bogs.

In the Hudson River drainage, a moraine blocked the rush of melting ice water on its way to the sea. When the thick ice was present, its sheer weight depressed the land, but its retreat northward allowed land south of the ice front to rebound, forming a large depression around the Hudson River between Glens Falls and Newburgh. The depression filled with water from the melting glacier, and created a 160-mile-long body of water called Glacial Lake Albany, which covered most of the Hudson Valley for the next four thousand to five thousand years. Ten streams flowed into the lake, forming sandy deltas at their mouths. The Mohawk River, an especially large tributary to the west, deposited the sandy sediments of the Albany Pine Bush, an inland pine barrens community that still has remnants of ancient sand dunes sculpted by winds thousands of years ago. Over time, the flat bottom of Glacial Lake Albany accumulated deep sediments of clay and loam. As the glacier continued to melt northward and the land rose with its retreat, the lake eventually drained into the sea through the Hudson River channel. It left behind rich soil for productive farmland and clay banks that provisioned a thriving brickmaking industry in the 1800s.

Beyond the shores of the ancient lake, the ice sheets left poor soils derived from ground-up rocks. The glaciers left thin layers of rocky soil on hilltops and somewhat deeper deposits in the valleys, where the ice sheets were thicker and moved more slowly. Rocks, along with the picturesque waterfalls, escarpments, farmland, lakes, ponds, and drumlins, are the legacy of glaciation in the Hudson Valley.

Glacial Lake Albany. Courtesy of New York State Museum, Albany, NY.

A Land Changed by Humans

Humans have lived in the Hudson Valley for at least seven thousand years. At first, their impacts were small. In 1609, when Henry Hudson traveled up the river that now bears his name, he encountered Native Americans living along its shores. In spring, summer, and fall, the Native Americans lived in small seasonal settlements that were close to the river. Here they fished from seasonal fish runs, gathered shellfish, and grew crops of beans, maize, pumpkin, and tobacco on the rich floodplain soils. In winter, they moved away from the river to more sheltered inland sites, where they practiced ice fishing on frozen ponds and lakes, trapped beaver, and hunted small game and deer. While it is well known that the indigenous people of the Hudson Valley burned clearings in the forest to plant crops and attract wildlife, their populations were small, and their disturbances were minor and temporary compared to those of post-European settlement.

That all began to change in 1623, when the Dutch established the settlements of New Amsterdam on Manhattan Island and Fort Orange near modern-day Albany. European settlers came to the Hudson Valley to trade and make money. Impressed with the abundant wildlife and fertile soil, they began harvesting and exporting the commodities of the New World. They established permanent settlements along the river and its tributaries, and exploited the rich soils and transportation routes the waterways provided. Over the next four hundred years, the population of the Hudson Valley grew, and its inhabitants altered the natural communities dramatically.

THE RIVER, ITS TRIBUTARIES AND SHORELINE

The Hudson River of today is nothing like the river that Henry Hudson explored in the seventeenth century. Studies have shown that the river between Athens and Troy was once a braided waterway with many secondary channels. It was dominated by intertidal and shallow water habitats of less than two meters in depth that included more than sixty islands (Miller, Ladd, and Nieder 2006). This river must have teemed with waterfowl, shorebirds, and waders. However, these shallows impeded navigation. Like many a modern boater, Hudson himself ran aground on a bank of ooze in the middle of the river near Castleton and had to wait for the next high tide to continue his journey.

After completion of the Erie Canal in 1825, efforts to improve the channel to Albany began in earnest. The state tried to reduce erosion from the riverbanks by constructing spur dikes that projected out from the shoreline into the current. The construction also blocked secondary channels to increase flow and scour a single narrow but deeper channel, through dredging where necessary. The federal government took over in 1831, and the Army Corps of Engineers built longitudinal dikes, still visible at low tide, parallel to the current to constrict the flow and increase scour (Collins and Miller 2011). Dredging increased, and the spoils were placed behind the dikes. Shallow areas were filled, and former islands were joined to each other or to the mainland, where they became part of the river’s floodplain. Today, periodic dredging continues on parts of the river between New York City and Albany to maintain the shipping channel at a depth of a little over thirty feet. The price for maintaining the Upper Hudson River estuary as a major commercial shipping channel has been the loss of nearly three thousand acres of shallows, many miles of shoreline, and more than forty islands, all natural communities that undoubtedly provided important habitat for many birds.

Like the Native Americans, European settlers lived close to the river to take advantage of the fertile soils and efficient transportation. Residential development, agriculture, industry, and transportation concentrated on the river’s shorelines. By the mid-1800s, the railroads linked Manhattan and Albany. Dependable year-round transportation made it possible to export more goods to New York City; this fueled industries such as ice harvesting and brickmaking, which further altered or degraded natural habitats.

Before refrigeration, from the early 1800s until about World War I, ice companies cut blocks of ice from the frozen river in winter. Steam-powered conveyors moved the large blocks into icehouses for storage and later distribution to consumers by boat, rail, or wagon. At its peak, the ice industry employed thousands of seasonal workers (Calandro 2005; Harris and Pickman 2000). Remnants of the more than one hundred icehouses that dotted the shoreline between New York and Albany, mostly on the middle and upper parts of the river, are still evident today.

The Hudson Valley brickmaking industry began in the mid-seventeenth century, but boomed in the mid-1800s, when horrific fires in New York City destroyed hundreds of wooden structures, and building codes required the use of more fireproof materials. Brick production made use of the clay left behind by Glacial Lake Albany along the shores of the river from Mechanicville to Haverstraw. The old clay pits are marked on topographic maps. On the landscape, the pits appear as deep hollows; and when explored, some remain littered with bricks from the past. Brickmaking continued in the Hudson Valley for nearly three and a half centuries, but declined as profits decreased when new building materials became available (Hutton 2003).

Harvesting ice on the Hudson River circa 1912.

New York State Archives.

THE UPLANDS

At the time of European settlement, land away from the river was heavily forested, except perhaps for small tracts burned by Native Americans for agriculture and wildlife (Day 1953). The warmer valley forests were dominated by oak and chestnut, while northern hardwood forests, composed of beech, maple, yellow birch, hemlock, and white pine, covered cooler sites including the Taconics and the Catskills. Some of the highest elevations supported extensive stands of spruce, fir, and paper birch (Cronon 1983).

When the Dutch and later the English arrived, they set about clearing the land for agriculture. They built dams on tributary streams, used waterpower to run sawmills, and then exported ship masts and firewood to Europe. Oak, chestnut, and especially hemlock, which grew in dense stands on north-facing slopes in the Catskills, were cut for their bark and used in the tanning industry through most of the nineteenth century. After the Civil War, farms were abandoned as agriculture moved west into the more fertile prairies of the central United States. The first farms to be abandoned were the least productive: those located on thin, marginal soil and steeper north-facing slopes. The more profitable homesteads on better soils hung on longer, but by the turn of the twentieth century, nearly all the forests in the Hudson Valley had been cut over at least once and sometimes two or three times (Swaney, Limberg, and Stainbrook 2006).

Because of farm abandonment, forest cover in the valley has increased over the last 150 years. However, because of their historic land use and past disturbance, the mature forests of today are very different from the relatively undisturbed primary forests that greeted European settlers. In today’s Hudson Valley, chestnut oak and northern red oak forests dominate the steep, rocky sites that were selectively cut but probably never used for agriculture. Poorer soils at lower elevations that were once pasture now support white and black oak and pignut hickory. Areas with the best soils, the ones used for cultivated crops, typically succeeded to woods of red maple and white pine woodlands (Glitzenstein et al. 1990).

Natural succession following farm abandonment took place in a world influenced by human activities. Abandoned farms were sometimes reforested with plantations of trees provided by government-sponsored programs. Chestnut blight and Dutch elm disease led to the decline and near elimination of the American chestnut and elm, trees that were common in the original forests. Today’s forests also contain nonnative plants that were not present on this continent before European settlement. Norway maple, tree of heaven, Japanese barberry, multiflora rose, Oriental bittersweet, and garlic mustard are all introduced exotics that are now common in many Hudson Valley forests.

Humans have also interfered with natural processes that play a key role in maintaining some kinds of forest communities. Natural fires fueled by oak leaves were important in maintaining the species composition of some forest types, especially pine barrens and oak-dominated ridges in the Hudson Highlands and Shawangunk (pronounced shawn-gum) Mountains. The elimination of fire has altered the species composition of these fire-dependent forest communities, which now favor red maples and black locust.

Along with the flora, forest wildlife has also changed. For example, without natural predators, which were removed in part by hunting activities and habitat loss, white-tailed deer populations have exploded. These herbivores devour tree seedlings, and this impedes natural regeneration of the existing forest habitat. Conversely, beaver population densities are likely lower now than during presettlement times, although these populations are on the rebound. Open beaver meadows in forest ecosystems significantly increase bird diversity (Smith and Marks 2008).

The Physical Setting of Today’s Hudson Valley

For practical reasons, the birdwatching sites in this book are chosen from the ten counties that border the Hudson River between the Troy Dam and New York City, but the Hudson River watershed extends well beyond these counties. The Hudson River collects water from a 13,326-square-mile area that includes not only most of the land in eastern New York, but also small parts of Vermont, Massachusetts, and New Jersey. The river travels 315 miles from its origins in the high peaks of the Adirondacks to the Atlantic Ocean in New York