Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[tulsaducati]

5-9-23:  Hard to believe, but DH2 is already 32 days old. We're seeing lots of changes now, with the juvenile feathers coming in on the wings and tail, covert feathers covering the base of wing and tail feathers, and contour feathers appearing on DH2's back. We've often been asked about how the feathers develop, and particularly if the juvenile feathers are produced from the same pores that produce the thermal down. Reading through Amy's blog, it's a far more complicated subject than I thought! It turns out, feathers do not sprout from pores that produce down. Complex feathers grow from follicles that become active after hatch. Juvenile feather growth really takes off at about 35 days, so we should see some exciting feather changes soon. Here's a link to Amy's blog on the subject: https://www.raptorresource.org/2023/05/01/from-bobble-heads-to-eaglets-natal-down-thermal-down-and-flight-feathers/

[smileawhile]

Coming to Terms!
Digitigrade - animal or bird that walks on its toes (digits) as opposed to -
Plantigrade - foot flat on the ground (humans).
Eagles are digitigrade (what a great vocabulary word!).  We see that starting in week 4 DH2 is gaining the muscle strength to stand.  The nest is certainly not a very firm, stable surface to practice walking but the challenge will actually help them strengthen those leg muscles.  This will enable DH2 to "prance" about on those huge toes to explore his/her beautiful home high up in the cottonwood.
and here is a link for everything you could possibly want to know about bird feet and legs!
https://en.wikipedia.org/wiki/Bird_feet_and_legs

[glogdog]

Flap, Flap, Flap!  We’re starting to see DH2, in the 5th week of life at the Decorah Eagle’s nest, begin to flap those growing wings.  “Wingercizing” as we call it helps to strengthen the wing muscles.   There are about 50 different muscles that control the wing movements, but the Pectoral muscles and the Supracoracoideus muscles, are the primary engines of bird flight.  The Pectoralis major is the primary depressor of the wing in downstroke.  The Supracoracoideus is the primary elevator of the wing in upstroke.  Here is a neat video showing how they work: https://youtu.be/aFdvkopOmw0   

[tulsaducati]

May 13, 2023:  DH2 is 37 days old! According to Dr. Bryan Watts, T90 (the time required to reach 90% of the terminal or final weight) is reached between the age 36 and 42 days, depending on the gender. The smaller sex (the male) is characterized by earlier development of feathers, faster attainment of asymptotic size (size that nears the peak of the growth curve) and earlier flights from the nest.  Most of an eaglet's weight gain, relative to its overall body weight, occurs early on. We've had lots of discussion about the sex of DH2, we would all love to know whether we have a boy or a girl. While both sexes are about the same size at hatch, the sexual size dimorphism begins to appear in some variables after 20 days of age.  Bortolotti found sexual dimorphism for bill depth to be present at 20-24 days, and for foot pad between 25-29 days.  These variables level off between 40-45 days. Although we have some clues about the possible sex of our eaglet, without another eaglet in the nest for comparison, we'll just have to keep wondering! As we continue to watch DH2 standing tall beside his parents, it's apparent that we are at or near 90% of his or her ultimate size.

[pyrmum1]

Covert feathers cover the bases of the flight feathers. They cover the leg from the upper leg to the abdomen on both the dorsal and ventral surfaces of the body and help streamline the shape of the wings and tail while providing insulation. 

[cwellsla]

Most of us will agree that the tail of an eaglet is just about the cutest thing ever. So let's talk about the structure of the tail.

There is a bone at the posterior end of the spinal column in birds called the "pygostyle" which consists of several fused caudal vertebrae and supports the tail feathers (number 17 in the photo). It is the main skeletal base of the "uropygium", the posterior part of the body from which the retrices, or tail feathers grow. The uropygium is the fleshy and bony protuberance at the posterior extremity of a bird's body that supports the tail feathers. Colloquially it is known as the bishop's nose, parson's nose, pope's nose, or sultan's nose.

[pelmomma]

Birds have large brains relative to their bodies and that account for about 9% of their body mass.  Many types of birds, particularly hunters such as bald eagles, show complex intelligence and learning abilities.

The optic lobes and the cerebellum (which helps coordinate muscles in flight) dominate the midbrain.  The two optic lobes are huge in relation to the rest of the brain. 

The olfactory lobes are relatively small in most birds, suggesting a poor sense of smell as with bald eagles.  Some birds, such as vultures, do have a well-developed sense of smell.

[oregonian1944]

We have often observed HM bringing in talons full of nesting material prior to forecasted weather changes. Here is an explanation as to why or how she can sense changes in the weather.

A bird's skin has sensory nerve endings that detect heat, cold, pressure, and pain. Touch is an important sense to them, especially in flight. They are very sensitive to changes in air temperature, pressure, and wind speed. These changes are transferred down the feathers to nerve endings in the skin. Filoplumes around the bases of major flight feathers have sensory corpuscles around the base of each feather shaft. As the remiges are moved during flight, the filoplumes assist the bird in judging what position its flight feathers are in and gives feedback as it shifts the position of its feathers. This allows birds to feel despite their thick covering of feathers.

[tulsaducati]

Eagles, like all birds, have superior color vision. They see colors as more vivid than we do, can discriminate between more shades, and can also see ultraviolet light — an ability that evolved to help them detect the UV-reflecting urine trails of small prey. In addition to the wider spectrum of color vision, we all know that eagles have much sharper visual acuity. Their retinas are more densely coated with light-detecting cells called cones than human retinas, enhancing their power to resolve fine details just as higher pixel density increases the resolving power of cameras. They also have a much deeper fovea, a cone-rich structure in the backs of the eyes of both humans and eagles that detects light from the center of our visual field. Some investigators think this deep fovea allows their eyes to act like a telephoto lens, giving them extra magnification in the center of their field of view. A big thanks to our deeply loved and sadly missed TX_Ninja, who taught us much about eagle eyes, and many other things. Fly high, TX.

[cwellsla]

At 12-13 weeks old, an eaglet's flight feather growth is developed well enough to leave the nest. Fledglings will begin to hone their flying skills and landing techniques as they begin the process of learning to find and kill prey. They will still depend on the parents for food for several weeks, and typically stay close to the nest tree as they learn how to forage for food. This period is used to complete feather growth and to develop muscle strength. Young eagles learn by watching their parents, and by practicing instinctive behaviors. Juvenile skills are perfected by trial and error, and within about a month after fledge, they will have mastered the art of soaring. By late summer, juvenile eaglets will be flying well outside the nest territory and learning to hunt and search for their own food. A juvenile eagle is nearly self-sufficient at an age of about 16 weeks. Eagles hatched in April will likely leave their parents' home range in September.

[glogdog]

"The ten weeks of nest life can be divided into three stages: eyas, this is derived from the French niais, meaning "fresh from the nest " and which refers to the first three to five weeks when the eaglet is covered with down, needs to be brooded frequently, and is unable to stand and feed itself; ramage, from the French word of the same spelling meaning "wild" or "of the branches," when the eaglet becomes covered by feathers, needs to be brooded only in harsh weather, and learns to stand up, hold food, and feed itself; and brancher, which for eagles is the one-week period near the nine- to ten-week age when they move out to the branches to strengthen their leg muscles and fine-tune their balance."
Excerpt taken from A Season with Eagles by Dr. Scott Nielsen.

[pelmomma]

DH2 has demonstrated this week that he can self-feed, but it will be a long time before this young bird becomes proficient. 

As we’ve seen, DH2 is also almost as large as his parents.  By 7 weeks of age, young eagles have attained almost their full fledging weight and very much look ready to fly.  But his tail feathers have only started to lengthen, and his wing feathers are well below fledging length. 

We’ll see increasing bouts of wingercizing in the coming days, followed by the excitement of hovering.

[cwellsla]

A bird has some 175 different muscles controlling the movements of its wings, legs, feet, tongue, eyes, ears, neck, lungs, sound-producing organs, body wall and skin.  Collectively, the muscles are concentrated near the bird's center of gravity.  Muscles are used for motion and balance and are the primary organs of heat production in the avian body.

The muscles that surround the cervical spine are numerous and complex.  They both support the cervical vertebrae and provide precise control over movement such as helping the head and eyes move rapidly.  Birds also need their long necks to reach and groom their feathers.  There are many thin overlapping sheets of muscles and except for the long dorsal and ventral midline muscles, are no longer than a third of an inch. The image below is a rough diagram of major muscles of the bald eagle.

[Iriscats]

Birds have the keenest vision of all vertebrates. It is the most important sense for the bald eagle. Bald eagles are diurnal (active during the day)
Their eyeballs are almost as large as humans, but they are fit so tightly into their heads that they can barely turn them in their sockets. In order to see in all directions, they have to tip or turn their head. Fortunately, their necks are very flexible, and can rotate their heads 270 degrees, unlike humans who can only rotate their heads 180 degrees.
 
The position of the eyes allows both monocular vision  where both eyes operate somewhat independently to see objects to the side, and binocular vision, where both eyes focus on an object directly in front of the head just like humans. Binocular vision gives them extremely accurate depth perception that allows depth of field-an important asset for a bird that has to pinpoint prey from great distances in order to catch it with their talons.
 
An eagle bobs its head up and down and from side to side in order to triangulate the distance to its prey (triangulation means measuring something using trigonometric relationship between pairs of sides and angles of triangles).  In effect, the eagle can use his eyes like a range finder. Not only can it spot prey at great distances, it can also judge how fast to fly to catch prey.
 
A bald eagle looking at a football field (or fish or other prey) would be able to see it from 32 football fields away, or just about 2 miles.
 
If humans had the vision of an eagle we could see a pin lying on the shoulder of a road while driving 65 mph!

[pyrmum1]

The calamus (sometimes referred to as the quill) is the part of the shaft closest to the bird’s body.  It is hollow and doesn’t contain any vanes.  The distal end of the shaft is called the rachis.  It is solid and is the area to which the vanes are attached.  The flight feathers of the wings are called remiges and are of two kinds: primaries and secondaries. Primaries are 10 in number and are those finger-like feathers that are attached from each wrist to the wing tip - they aid in providing forward lift or thrust in flight and can be adjusted individually to help in stability and maneuverability during flight.  Secondary flight feathers, or secondaries, are mid-wing and are 16 in number.