10/22/2010

Bald Eagles and Big Trees

You need big trees for birds this large

Bald eagles are forest creatures requiring large territories that contain big trees close to water for nesting and perching. Only large, old trees have the strength, height, and branching structure that eagles require. The loss of such trees has been partly responsible for their drastic drop in numbers. Eagles need big trees.

The nest of a bald eagle is known as an Eyrie. It is one of the largest bird nests in the world, and can weigh as much as 2 tons. The nest consists of sticks and branches wedged together to make a large mass of material. Only sturdy, old trees can support these heavy structures.

Bald eagles use the same nests every breeding season. They keep adding new materials year after year. They line their Eyries with twigs, moss, feathers, and grass. A new nest is typically 2 feet deep and 5 feet wide but can grow enormously over the years. If a nest is destroyed for any reason, then the bald eagles usually remake their nest in close by areas. Eagle pairs will often use the same nest site for their entire breeding life.

Eagles also use large trees that emerge from the surrounding canopy to perch on. From these emergent trees the eagle can survey their territory for prey and other eagles.

Bald eagle nesting territory

Some of the trees surrounding Sooke Harbour are large enough to support massive eagle nests. A couple of years ago the largest, tallest tree in a forested area in my neighbourhood was toppled in a storm. For many years this tree provided the scaffolding for a giant nest that a pair of eagles had used faithfully season after season. I watched several baby eagles fledge at that site, and was sad to see the tree laying on the ground when I went over to investigate. The ton of material forming the nest may have been responsible for the tree toppling over.

One year I watched a baby eagle from this nest learning to fly along the edge of the forest. It flew to a tree and landed on a branch. All of a sudden the young, inexperienced eagle lost its grip and swung upside down on the branch with its wings spread wide. It stayed hanging like this for almost a minute, not seeming to know what to do next. Then it released its grip, took flight again, and landed in a more upright position. Kids do the funniest things.

Local eagles love this big tree
After the neighbourhood nest was lost the eagle pair relocated to another large tree within their territory. Close to the new nest site is a very tall tree that was used this year by a fledgling eagle learning to fly. The eaglet, perching on a sturdy branch would spread its wings, catch the wind and hop up and down in brief mini-flights.

Most eagle nest trees on the east coast of Vancouver Island (81%+) are veteran Douglas-firs over 150 years of age, usually found within a kilometre of the shoreline.

99% of old growth Douglas-fir forests on southeast Vancouver Island have been logged, and a great deal has been developed. Until recently, enough small stands of old growth, or lone veteran trees amongst smaller second growth, have remained to support a sizable nesting eagle population. However, continued development and logging of lands have caused the loss of nest trees, threatening the long-term maintenance of their numbers. Eagles need big trees.

In British Columbia landowners having eagle nests on their property are required by law to develop a management plan showing how the nest tree is to be preserved.

4 comments:

  1. i miss sitting under my "eagle tree" as i called it, on whiffen spit... what a delight to sit under a tree with an eagle perched above me watching the sky and waves. perfection.

    ReplyDelete
  2. Lulu Rose,

    Whiffen Spit is a beautiful place, and there are always eagles around. Nice that you have been able to enjoy them at your eagle tree. Perfection, indeed.

    ReplyDelete
  3. Anonymous25/3/13

    Hi there,

    I had hoped that perhaps you'd check your blog for factual accuracy before posting it.

    You've posted that bald eagles are forest creatures; in fact they are not.

    Bald eagles are found right across across North America, in all types of landscapes-- forest, lakes, plains, prairies (reservoirs, lakes, marshes ponds), mountains, and ocean. Although they are primarily fish eaters, they will also hunt small mammals, and will eat carrion.

    I live in the middle of the prairies and today I spotted no less than four bald eagles congregating near a pond. Between February and November I see them on a regular basis, as well as golden eagles, red-tailed hawks, snowy owls, great horned owls,and Swainsons hawks. In the spring and fall trumpeter swans and snow geese pass through here by the hundreds, and pelicans are seen at my favorite fishing hole all summer.

    Just wanted to point out that bald eagles are not strictly forest creatures.
    cheers

    ReplyDelete
    Replies
    1. Bald eagles need trees for nesting, perching, and roosting. I have also seen Bald eagles on the prairies where they liked to hang out in the river valley and hunt for ducks. These birds enjoyed the Black cottonwood trees along the river and we would often see them perched on the twisted branches.

      In my area on the west coast, big trees are a major factor in the life cycle of the eagles. Since harvesting has removed most of the big trees these birds require to hold their gigantic nests (that can weigh up to a ton), eagle numbers have been dropping.

      Thanks for visiting and commenting.

      Delete

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