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New England Seabirds

 Wilson's Storm-petrel  Dave Jones

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Seabird Areas in New England

By Emmalee Tarry

Pelagic Birding Directory

Seabird Areas New England

The Continental Shelf Edge

Nor'easter Birding


Norfolk Canyon Under sea feature

Finding The Birds and Other Sea Animals
On a map the ocean is blue. It would seem that birds and animals would be dispersed evenly across the beautiful expanse of the ocean. Any fisherman can tell you this is not the case. Why not? Animals go where there is food and the food is not evenly distributed across the ocean. You may have heard that  Stellawagn Bank is a good place to find seabirds around here because there the birds find food. To find the birds you need to know something about the bottom of the sea which is not a flat plane but as wrinkled as the land with mountains,valleys and deep trenches.

Ocean Zones
The ocean can be divided into 4 zones:

Tidal Zone
The area covered by water at high tide and exposed at low tide.

Continental Shelf
The area from the tidal zone to the edge of the continent.   This area slopes to 200’ and varies in width. The continental shelf was dry land during the last ice age with rivers that emptied into the ocean and hills and valleys. As the glaciers melted they left deposits on the shelf which became underwater features when the water got deeper. Cape Cod is an example of glacial deposits still above water while Stellwagen Bank consists of glacial deposits now completely covered by water.

Continental Slope
The area where the depth increases rapidly. The canyons of the slope are the old valleys formed by rivers that flowed across the shelf and emptied into the ocean. See the illustration of Norfolk Canyon above.

Deep Sea
The floor of the sea is not flat and featureless. There are mountains (ridges), valleys, basins and  very deep trenches.

Gulf of Maine - Ocean Zones
In this map of the Gulf of Maine and the area directly south of Cape Cod, the shallow areas are lighter blue. The darker the shading, the deeper the water. All of the Gulf of Maine is on the continental shelf. The continental shelf edge south of Cape Cod is labeled "The Canyons".

During the last ice age when the ocean was some 300' lower, the continental shelf was dry land. The canyons were formed by rivers that flowed into the ocean.

Banks are shallow areas some of which were formed by glacial deposits. Cape Cod was the terminal morraine of a large glacier that is still above water.

Stellwagen Bank which is the fat "C" shaped area just north of the lower arm of Cape Cod is also a glacial deposit that is now covered with water. It was formed by the same glacer that formed Cape Cod.

Other banks represent rocky ridges on the ocean bottom. Jeffreys Ledge the light blue snake like area off the coast of New Hampshire is such a ridge.  These ridges are hill or  mountains that at one time would have been dry land when the ocean was 300' shallower.

Gulf of Maine  Ocean Zones

What is Necessary for Life?
Life needs energy which it get from food. Plants take carbon dioxide, water and sunlight and make plant parts in a process called Photosynthesis.  Plants need sunlight to grow and light only penatrates water to a certain depth. Plants also need certain minerals such as Nitrogen, Potassium, Phosphorus etc. Minerals that gardeners frequently add as fertilizer to their gardens. These salts and minerals are found in the land and they wash into the oceans from run off and in rivers.

Animals cannot absorb sunlight and create their own food. Animals eat plants or they eat other animals that eat plants so they must go where plants can grow.

The problem in the ocean is that when a plant or animal dies, the minerals make their way to the bottom of the ocean. Here there is no light and no plant can utilize the minerals. They remain unavailable to plants. The animals that live on the bottom of the very deep ocean must depend upon dead plants and animals that sink to the bottom.

So the problem is the fertilizer in the ocean is near the bottom where the plants can't get it. The light only penetrates a few hundred feet into the ocean. Plants need both fertilizer and light. So much of the ocean is limited in supporting photosynthesis..

Certain structural features of the ocean bottom cause bottom water to rise to the top. These upwellings bring bottom water containing minerals into the light zone where they can be utilized by plants. Here where phytoplankton (small plants) grows we find birds, mammals, and fish.

Upwellings can be caused by an underwater current flowing into a ridge or mountain on the ocean bottom. Like wind hitting a tall building, the current is deflected toward the surface. The drawing to the right illustrates such an upwelling.

Upwellings can also be caused by a cold current meeting a warm current. The colder water slides under the warm water causing the warm water carrying minerals to rise. This explains the Antarctic convergence where the cold water from the south moves north to meet the warm water of the tropics. Birding trips to Antarctica usually sail along the Antarctic convergence because of the life to be found there.

When the water rises it brings nutrients to the surface where small plants (Phytoplankton) get sunlight and can utilized the nutrients to carry on photosynthesis. As these small plants grow they feed small animals (Zooplankton) which in turn feed larger animals and up the food chain.

Sea Mountains cause upwellings

Stellwagen Bank - Upwellings and Birds

This computer generated map is used with permission of Rich Signell of the U.S. Geological Survey at Woods Hole.

The blue area to the left (west) of Stellwagen Bank is known as Stellwagen Basin. The depth in the basin is over 300 feet. Once you cross over the banks the depth decreases to 70 - 100 feet. Stellwagen Bank is steeper on the west side than it is on the east side. As the current encounters the steep sides of the bank it rises bringing nutrients to the surface. These nutrients feed phytoplanton and in turn small fish called sandlance. Larger fish, birds, and whales feed on the sandlance.

As your boat leaves the harbor of Boston or Gloucester, it will cross the blue area that is Stellwagen Basin. Here you will see few birds or mammals simply because there is little food.

Abruptly you will arrrive on the bank and if is going to be a good day, you will start to see birds.  The birds and mammals are feeding on sandlance a small fish that prefer sandy bottoms.

Stellwagon Bank

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