Bald Eagles spend over 90% of daylight hours perching in both winter and summer. Some have been monitored for perching and have been found to have done so, unmoving, for up to eighteen hours.

Perches have a great significance to the eagle, but they are more flexible in choosing perches than they are choosing roosting or nesting sites. Perches allow eagles to loaf or rest and give the eagles a place from which to hunt and forage.

Many times they will eat from the same branches in which they’ve perched. Eagles can use guard or sentry perches as lookout points while watching their nests, food, territory or young. Perches can also provide a way to send messages to other eagles about occupied territory, location of food or roosts, or even willingness to mate.

Typically feeding perches will be within sight of the water or even hanging over the water on exposed limbs. Sentry perches are within easy sight of a nest or a roost. Feeding perches will many times be in heavily forested areas out of the direct flight path. This is to prevent or deter other eagles from stealing their food.

Cottonwood trees are widely used as perches along the Mississippi River. Cottonwoods can reach great heights (sometimes 100 feet) and taller ones are referred to as “super canopy” trees. Eagles will perch on other things, like rocks, riprap, driftwood, ice and sometimes even fences, but they prefer natural perches.

Eagles will select the highest perch that can support their weight. They nearly always perch in the upper half of the tree and, if the branches are strong enough, the upper quarter. Relative to the surrounding tree canopy the eagle will choose those perches that tower above.

Eagles like a clear, unobstructed view of the territory they have just chosen to perch in and will choose branches that are horizontal, thick and easily accessible. Their large wingspan requires open areas for landings and takeoffs.

Roosting

A roost is an area where eagles will sleep during the night and rest or seek shelter on inclement days. They may gather in large communal roosts during the evening, but some birds remain on their daytime perches all night. If the weather is particularly bad (high winds, driving snow or rain) the eagles may choose to remain in the more sheltered roosts all day.

Roosting habitats do not need to be close to water. Eagles prefer to have sources of prey nearby, but it is not critical for them. More important is the shelter that this roost area provides.

Eagles will choose a roost for its protected “microclimate.” It typically will have tall trees that rise above the canopy of trees, and it will have clear views and open flight paths. In the winter many birds may roost together in these sheltered areas. These roost areas can contain just a few trees and attract only a few eagles, or have up to 100 trees and attract over 100 eagles.

These roost areas feature a weather pattern different from the general weather of the day, often caused by habitat and landform characteristics. The roost can be sheltered when they occur in depressions, steep-sided valleys or on the slopes of the lee side of a prevailing wind. Vegetation also helps protect the eagle from unfavorable conditions (conifers, for instance, provide much more protection from inclement weather than do deciduous trees). High winds in a roost area have proven to increase wind chill and can flush warm air from the roost, lowering the air temperature. Protection from rain and snow has proven less important than protection against wind.

Studies have shown that eagles conserve energy by roosting in protected habitat. An eagle can conserve as much as 5% of its daily energy requirement by protecting itself from adverse weather conditions. The death of an eagle as a result of cold is uncommon, but cold stress increases the demand for energy and therefore the need for food. If the food is easy to get, a cold-stressed bird simply eats more, but if prey is scarce, cold stress and food stress can be a deadly combination.

Foraging

The foraging  habitat is the most necessary habitat used by bald eagles. It must provide enough food consistently and have a minimal amount of human disturbance. This habitat needs to have large, open areas where prey can be killed and eaten. They prefer a wide visual field and need open areas to take flight and land.

Eagles require a large amount of food and may cover hundreds of miles to locate adequate supplies. This may mean that the birds will congregate below locks and dams or hydroelectric plants that have turbines churning the water. The turbines will stun or kill the fish and provide an excellent meal for the opportunistic eagle. Areas where there are large gatherings of waterfowl typically yield those that are injured or ill, also providing an excellent source of food.

Nesting

Nest sites are always located near water. If trees near water are inadequate, eagles will sometimes move farther inland.

Usually the eagle will nest in a tree. Here along the Mississippi River, eagles nest in cottonwoods. White pines are the choice in northern Minnesota, Wisconsin and Canada. No matter what species of tree is chosen it is usually one of the tallest in the surrounding forest. A tall tree allows adequate support of f a large nest, an open flight path, and an excellent surrounding view of the neighborhood.

Typically, eagles build their nests slightly below the treetop with some tree foliage and branches above them. This might help protect the adults and young from rain and sunlight. It is also believed that those trees with cover require fewer repairs each year because they are somewhat protected from the elements. However, there are a few records of eagles nesting in dead trees.