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[oregonian1944]

DH2 is fast approaching 8 weeks old and you can see he is already well-feathered and is about 90% of his mature weight. You may see his wings drooping at times because his developing feathers are blood filled which can cause the wings to be heavy. Now is the time when we may see him begin to practice "hovering" (sustaining air briefly but remaining above the nest) and practice landing. He has already developed the aggression for grabbing or stealing food from the parents. This is the time we will see lots of activity while he is learning many things, running, jumping, trampling, wingersizing, hovering, etc. Sit back and enjoy watching him. (Note: we don't know his gender, but I always refer to our DH2 as he)

[tulsaducati]

Eaglets about 60 days old are well feathered, and have achieved more than 90 percent of their mature weight.  Their growth is so rapid that a standing eaglet may occasionally droop its wings, since the developing feathers are blood filled and the wings can be heavy. The entire set of primary and secondary feathers is growing at the same time. We have seen our eaglet's hop-flap technique improving daily, getting both feet off the nest.  https://youtu.be/6xj0nN3_8hc

DH2 will soon practice "hovering" (which is sustaining air briefly but staying above the nest - think helicopter) and practice important landings.  Wing flapping and hovering also strengthens their pectoral muscles necessary for flying.  Other exercises they can perform are treading, trampling, and prancing which might help them later in subduing prey.

[pyrmum1]

Birds vary greatly in their cognition skills, in ways that affect an individual bird's survival and reproduction.  Large brain sizes in bald eagles (9% of their total body mass) require longer incubation periods to mature.  Foraging skills, breeding, parental care, long life span and even play behavior all correlate to the brain sizes and cognitive abilities of birds

[pelmomma]

A bald eagle’s hearing is not quite as highly developed as its vision, but still extremely sensitive.  Ears are simple openings in the skull below and behind the eye.  They are only visible in the first week or two after hatch and are then covered by sparse feathers called ear coverts or auricular feathers.  These auricular feathers will protect the bird's ears in flight.  The muscles that anchor these feathers form a shallow funnel which directs sound into the ear. 

The ear opening leads to an eardrum or tympanic membrane that covers the middle ear.  Sound waves are transmitted by the eardrum to the inner ear, also known as the labyrinth, where they are transformed into nerve impulses that are transmitted to the brain.  Semicircular canals in the labyrinth also assist in equilibrium. 

Scott Nielsen makes the point that the bald eagle never reacts just to a sound but always follows any noise it hears with a close visual examination of where the sound came from—if the visual observation confirms a threat, they will leave the area.

[Iriscats]

Fishing
The bald eagle is also referred to as a fish eagle because some studies show an average of about 56-90% of its diet will consist of fish.   Bald eagles use a number of techniques to search for and catch prey. When a fish is sighted, they will usually descend quickly and smoothly from their perch.  The eagle starts at a high angle and has an idea of the location of the fish.  As it gets closer, it glides in at a bend that becomes steeper until it nears the fish.  At the water's surface the eagle will reach a foot (or both feet for a larger fish) and carry it off.  Occasionally when capturing a larger fish, the eagle will plunge into the water and may not be able to take flight with its prey. In such an instance, it will tow the fish to shore swimming awkwardly, stroking the surface of the water with its wings while pulling the fish with its talons to shore. Another less common way to fish is wading into shallow water where smaller fish are available.  According to Mark Stalmaster  in his book, The Bald Eagle,  an eagle will wade up to its belly, submerge its head and strike with its beak.  "Generally they  can carry approximately 4 pounds of weight in their talons, but I will delve deeper into that on another Fact of the Day"
 
Eagles more easily recognize fish that are upside down (white side up). White side up fish are more quickly spotted and caught as they are more visible to eagle eyes.
 
Young eagles are much more likely to "catch" fish that have washed up on shore or fish that are floating rather than swimming.

[pyrmum1]

The nervous system is divided into 2 main parts-the central nervous system (CNS) and the autonomic nervous system (ANS).  The CNS is responsible for voluntary reactions of the body, such as movement or flight.  The ANS is responsible for the coordination of involuntary actions of the organs, intestines, blood vessels and glands.  The primary function of the nervous system is to integrate the functions of the body.  Proctor & Lynch state that the central nervous system receives stimuli from within the body and from the outside world through the sense organs and peripheral nervous system.  After processing the information, the central nervous system sends motor signals through the spinal cord and peripheral nervous system to control the bird’s movements and reactions to the world around it.

[tulsaducati]

The next milestone we are watching for should occur soon, around 9 weeks of age. Branching is defined as a direct flight to another branch (vertical or horizontal limb) in the nest tree…not a walk up, not a hop-flap, but a flight. A little wind assist is fine, but the prerequisite is wing powered flight.  Scott Nielson defines this term as "the one-week period during the nine-to-ten-week age when they move out to the branches to strengthen their leg muscles and fine-tune their balance."  He also says they use this developmental phase to strengthen their grip which will be important not only for perching and landing successfully after flight, but also for grasping their own food.

[glogdog]

Here is some Eagle terminology information as it pertains to the various stages of growth and development: Eaglet - anytime from hatch to about 10 weeks after leaving the nest; Hatchling - 1st week; Nestling - after 1st week until fledge; Fledgling - While perfecting flight – after taking their first flight; Juvenile - when the 1st coat of feathering grows in and for the 1st year; Immature or Sub-adult - after 1 year until adulthood. Some of these periods of growth can overlap.

[oregonian1944]

Air pressure is what enables a bird to fly. Air passing over the top of the wing must travel faster than air going beneath it; therefore air pressure decreases above the wing generating lift. In order to have air moving over and under the wing, the wing must be moving. This is called thrust. Thrust is created when birds flap their wings using their strong breast muscles.

Tails are important to bird flight and is comparable to rudders of ships and boats. The tail feathers help the bird steer and maneuver while flying, as well as providing stability as they take off and land. By twisting the tail, they can change direction mid-flight. By flaring out the tail, it helps the bird to slow down, creating drag and decreasing the bird's velocity.

[Bob1603]

Raptors’ memory is generally very good and aids birds in migration. Like a lot of humans,
raptors’ comprehension, and ability to recall is better for sights than for sounds-but their
sharpness of vision and ability to recognize things is much better than ours.

Nick Fox’s observations on memory relate mainly to trained raptors. He tells a wonderful story
about an old goshawk that he had trained who used to sit silently on her perch outside in his yard
surrounded by his students. As soon as she saw part of Fox’s head appear in the window, she
would call to him immediately. He also says that trained hawks will recognize their owners after
more than a year of absence and remember the meaning of the lure used as bait as well as the
hood the trainers use.

[pyrmum1]

As in mammals, a bird’s skin has sensory nerve endings that detect heat, cold, pressure, and pain.  Birds don’t rely on touch as extensively as humans, but it is still an important sense to them, especially in flight.  They are very sensitive to changes in air temperature, pressure, and wind speed.  Those changes are transferred down the feathers to nerve endings in the skin. Filo-plumes are numerous around the bases of major flight feathers that have sensory corpuscles around the base of each feather shaft.  As the remiges are moved during flight, the filo-plumes assist the bird in judging what position its flight feathers are in, and give it feedback as it shifts the position of its feathers.

[pelmomma]

Dispersal is defined as the purposeful movement away from population centers that serves to separate individual members of avian populations in one area.  Juvenile bald eagles generally leave their natal nest area and begin their adventure when they are no longer dependent on their parents for food.  The results are a mixing of individuals hatched at different locations. 

Dispersals are often undertaken by recently fledged birds and serve to increase population ranges and reduce population densities so that the birds that disperse are more likely to survive and reproduce than those who do not disperse.

[Bob1603]

Triangulate means to determine a point in three dimensional space. Raptors do this by bobbing their head or moving it in circles to determine how far away an object is. 

[oregonian1944]

There are 3 areas of concern to a breeding pair of bald eagles, the nest site, the breeding/nesting territory and the home range. The breeding/nesting territory is about 1-2 square miles and the home range territory is about 10-15 square miles. The more densely populated the area is, the smaller the range is. Eagles will defend their breeding territory from would-be intruders, with the nest site being their primary focus. Gary Bortolotti points out that spending a large portion of their day perched at the top of a tall tree, with bright white head in full view, serves as a signal to unwanted visitors. A mated pair will often perch side by side facing in opposite directions for the purpose of territory defense. Eagles search for food in their home range but they do not defend it.

[pyrmum1]

Birds do not have vocal cords, but rather vocalize with a muscular organ, the syrinx, located where the trachea divides to enter each lung.  A stiff membrane protrudes into the syrinx and produces sound when it vibrates, similar to a reed in a clarinet.  Muscles along the outside of the syrinx adjust in length and tension to produce different pitches.  A raptor’s syrinx is simple and does not produce the variety of sounds as a songbird, for instance, which may have numerous thick strands of muscles at varying angles around the syrinx.