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[Iriscats]

One thing we don't have to worry about in Decorah, is a deficiency in their diet, which would slow down or stunt the growth of the long bones in week 3.

This is also when their brain is developing. According to Nick Fox, most of the sensitive period of aspects of imprinting is at this time.

[pyrmum1]

At three weeks, the eaglet is pretty well covered with its second coat of down (thermal down).  Around days 18-22, natal down has all but disappeared except for the head

The eaglet's legs begin to change to yellow at three weeks of age. Their weight gain during days 18-24, is around 4 ounces a day. This weight gain is a bigger weight gain than any other time in their development.  By the end of the 3rd week or beginning of 4th week, their weight may be about 5 pounds and they may stand about 1 foot tall.
 

[smileawhile]

for April 21

[/b]
Coming to Terms
Thermogenesis - a fancy word for shivering
Although temperatures are finally warming up, Decorah can still have some cool mornings, or even cool days. 
Chatters have noticed the eaglets shivering sometimes when not shielded by a parent.  Birds and most critters, including humans, have this capability.  The muscle action of shivering generates heat to help keep the core warm.  Now the eaglets are sprouting a good insulation of thermal down, so thermogenesis and thermal down (thermoregulation) will help keep them warm when not being "tented" by Mom or DM2.

[jfrancl]

Today 4/21, the eaglets are 16 days old and 13 days old. At 2 weeks of age the nestling should instinctively back up to the edge of the nest and defecate over the side.

They will have unique calls that prompt adults to bring them food. Their gray thermal down is replacing the natal down. They are approximately 2 pounds now and will be brooded less often.  Beaks and clown feet are growing fast, and now the eaglets will be exploring the nest more.

 https://www.raptorresource.org/2019/04/12/eaglet-growth-and-development-week-two/

[Pansie]

The Curious Case of the "Crop'
 The crop, that muscular pouch near the gullet or throat, has drawn the curiosity and amazement of many a viewer. The questions abound: What is it? How much can it hold? Can it get any larger! Do all birds have a crop?

The crop is a pantry of sorts, below an eagle's chin, which temporarily stores food. It is an expandable section of the esophagus. An adult eagle's stomach is quite small, about the size of a walnut. The eagle can eat up to 1/3 of their own body weight in food. The food is stored in the crop, where it is moistened, softened, and then moved through the digestive tract as needed.

It never ceases to amaze viewers how large the crop can get! At times it's a wonder the eaglets can maneuver with that large protruberence! To our surprise and laughter, they handle it quite well!  In a adult eagle, the crop may be visible when the feathers are blown about in the wind.

Adult eagles do not need to eat daily. In the case where food sources may not be readily available, an eagle can gorge on food that is available, and hold up to 2 pounds of food in their crop.

Not all bird species have crops.

Hopefully this bit of information will ease curiosity a bit, however, isn't it marvelous how nature has taken care to ensure that our loved Raptors will eat well!

[Iriscats]

According to US Fish & Wildlife Service, bald eagles have been found to prey or take as carrion 46 species of birds, 20 species of mammals, 18 species of fish, 5 species of turtles, and 2 species of invertebrates.

On Decorah nest prey seen in the past has included, cottontail rabbit,muskrat,fox, squirrel, grey squirrel, coot, gosling, grebe, various other birds, fawn (likely road kill) piglet, raccoon, and fish including rainbow trout,redhorse sucker and white sucker.

That's why it is sometimes difficult to tell what has been brought in.

[eaglesrock29]

For April 23, 2020

At 18 days old today, D34 and D35 are beginning their rapid growth period, which comprises Days 18 through 24.  During this time, eaglets gain about 4 oz per day, more weight than at any other stage of their development.  The size difference between females and males will begin to emerge after 20 days.  Gary Bortolotti found that sexual size dimorphism* for bill depth is present at 20-24 days and for foot pads, between 25-29 days. 

While females gain weight faster than males, males develop their plumage and achieve other milestones faster than females. 

There are so many things to observe and learn over the next week!
_______________________________________

*In birds of prey, generally the female is the larger gender (approx 25% larger and up to 30%)

[smileawhile]

for April 24, 2020

Eaglesrock has posted a very informative FOD on eaglet development, so to continue the topic I would like to add this tidbit of information -
Mark Stalmaster, in The Bald Eagle, tells us that the bald eagle has an S shaped growth curve.  Development is rapid the first month, slows
during the second month, and levels off in the third month.  In that time the eaglets will grow from about 3.5 oz to 8-10 or 11 lbs, depending on the sex.

[tulsaducati]

This week we start to watch for the appearance of pin feathers along the edges of the eaglets' wings. Pin feathers are new developing feathers that are surrounded by protective keratin sheaths, and they begin to appear at about two to three weeks old. While a feather is growing, it contains nerves and blood vessels, and the base of the feather shaft is blue from the blood supply.  Once the feather has hardened and the base has turned white, the blood supply has rescinded and is no longer flowing to the feather.  The feather is then referred to as hard penned. You can see closeups of pin feathers in this video at 8:08 in: https://youtu.be/D6muMqT17wI.

[glogdog]

Everyone seems to enjoy watching young eaglets do "poop shoots" out and over the nest.  So what exactly are poop shoots made of?  They are made of feces, urates, and a clear liquid part.  The final form of waste excreted is a white semi-solid.  The proper term to use when describing eagle defecation when it is seen is "sliced".  The white strand of projected excrement is properly called a slicing.  Bird droppings are also called mutes.

https://youtu.be/f9OPtqv5Bg0

[jfrancl]

Adult bald eagles require approximately 1 to 1.5 pounds of fish/prey per day.  This includes energy for metabolism and maintenance as well as energy for flying, hunting and other activities.

Energy demand for eaglets includes maintenance requirements, plus energy for growth and development.  Peak energy demand occurs in the later stage of rapid growth when metabolic demand is high due to large body size and when eaglets are still growing at a rapid rate.  After terminal size is reached, energy demand declines to that required for maintenance alone and resembles that of adult food intake. One reliable outward sign that chicks have moved past the period of most rapid growth and peak energy demand is when they begin to appear mostly feathered.

[pyrmum1]

From the USFW states that there are 5 phases of sensitivity relating to human activities & nesting bald eagles:

Phase 1: Courtship & nest building.  This is a sensitive period & can result in eagles leaving the nest for good.

Phase 2: Egg Laying.  Human activity can cause eagles to desert/abandon the eggs for the season.

Phase 3: Incubation & Hatching. A sensitive period where adults take wing suddenly due to human activity & this leaves the eggs vulnerable.

Phase 4: Nesting period 4-8 weeks. This is a sensitive period due to nestlings missing feedings & this can affect their survival.

Phase 5: Nestlings 8 weeks to fledging. This is a very sensitive period to human activities. This could cause the nestlings to prematurely fledge and perish.

As you can see, any human activity can have devastating effects on nesting bald eagles. When visiting a nest area, if an eagle stops its activity, i.e. preening, looks toward the activity it hears, such as loud voices, etc., then you have disturbed the eagle. It is always best to stay a long way back from an eagle's nest & use binoculars. The view will be great & no harm is done to the eagles by viewing in this manner.

[Iriscats]

When eagles roost along rivers, lakes or reservoirs they are most likely to choose deciduous trees. In the midwest they prefer cottonwoods.

The scientific name is Populus deltoids. Common name is Eastern Cottonwood.   Like the eagles they are the fastest growing commercial forest species in North America. A young tree can add 6 ft or more each year. Bark is thin and smooth on young stems, but develop into gray to almost black and heavily fissured mature trunks.   The average tree is 60-100 foot tall with 60-100 foot canopy spread. Trunk diameter is 5 to 6 feet.

Cottonwoods are closely related to poplars and aspens with which they share the trait of shaking, shimmering heart shaped leaves which turn bright yellow in the fall. Cottonwoods can be either male or female. It is the female that produces fluffy white cotton like seeds.

[Pansie]

Tough as Nails
Consider the 'talon', the razor sharp part of an Eagle's foot that serves various purposes such as mobility, perching, fishing, hunting,and defense.

According to Peter Nye, with the New York Department of Environmental Conservation, eagles have 4 talons (and toes) on each foot. The halluxtalon  is the longest and heaviest and faces backward. In humans the hallux would be considered the big toe. The other three toes (and talons) face forward. Each toe is covered with keratin scales and is tipped with a talon that is approximately 2-3 inches long. As with an Eagle's beak, the talons are a constantly growing layer of keratin, over a core of bone, and like the beak, they are kept in check by constant wear.

The color of an Eagle's talon is due to carotenoids which are organic pigments. The underside of each toe is covered with spicules (fleshy knobs) that aid in gripping limps for perching, and also gripping prey during flight. It is interesting to note that when an eagle is carrying it's prey during flight, it carries it away from it's body and eyes, thus protecting itself from any harm.

A good point of reference is the fact that a talon is similar to a dog's nails. 

[oregonian1944]

During the 3rd week the eaglets brains are developing. You've heard the term "imprinting".  Eaglets first imprint on the sound and then the sight of the parent as a food source.  Secondly, they imprint on their siblings at about the time they are getting their secondary (thermal) down. Once they have imprinted on their parents and then their siblings, they also have imprinted on their nest, surrounding area and their fear response develops.  Anything that is unfamiliar to them now, elicits the fear response, such as a human, an animal, or other avian. According to Nick Fox, "this is the most sensitive period for the various aspects of imprinting.