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[Bob1603]

Many of you know or have heard about the Cornell Lab of Ornithology at Cornell University. For your reference the Lab has a phone app that will help you identify over 1,000 songbirds as well as more than 7,500 birds you can ID through photos. Here is a description about the app from the Lab's homepage:

In 2014 we introduced our free free Merlin Bird ID app, designed to help people answer their #1 question: What’s the name of the bird I just saw? The app works amazingly well thanks to its “smart” approach: users answer a few simple questions or snap a picture and then the app uses eBird data to present a short list of possibilities tailored to your location and date. More than a million downloads later, the app is more powerful than ever—it now covers more than 37,0500 species across 40 countries, and it can even ID birds in photos., and now it can even ID birds singing around you!

Here is a link to that webpage.
https://www.allaboutbirds.org/news/get-more-from-merlin-bird-id-with-these-powerful-features/#

[Bob1603]

Eagles hatched in April will likely leave their parents' home range in September, traveling irregularly and unpredictably. Until then, they generally stay within a mile or so of their natal nest. Stalmaster tells us that through their 20th week, seven weeks after fledging, most young are still within approximately .9 miles of the nest. On average it takes about 4-12 weeks for young eagles to start hunting successfully. Expert fishing and hunting skills probably take years to develop.

[glogdog]

At 12-13 weeks old, the fledgling's flight feather growth is developed enough to leave the nest. Some researchers have estimated the wing and tail development and growth at about 95% during this stage.   Similarly, their flight muscles don't fully develop until after they've started flying. Scott Nielsen states that up to five weeks is required from the time the eaglets leave the nest until their flight feathers are completely formed. This period is used not only to complete feather growth, but also to develop muscle strength and improve flying skills.

[smileawhile]

A review of the feather development in eaglets. As Glogdog stated in the previous FOD, flight feathers have still not completely developed by the time the eaglets fledge and will have about another five inches to grow.  Feathers grow from the tip first, with the base of the feather being the last to develop. At this time it is somewhat fragile and susceptible to damage. Once the feather has completed growth, the feather shaft hardens (known as hard-penned) and ligaments and tendons have grown and connect the feather to the wing bone, making for a much stronger, sturdier flight feather for our fledged eaglet!

[tulsaducati]

Along with flight feather growth, the last stage of development for the nestling is neurological and behavioral, learning coordinated movements.  Typically fledge occurs between 10 to 13 weeks of age.  Researcher Gary Bortolotti stated that males 1st flight average 78 days (68-84 day range), females 1st flight average 82 days (78-88 day range).  DH2 may venture out to a branch, or may fledge without ever branching.

When the chicks are young, peak energy demand occurs in the late stage of rapid growth when metabolic demand is high.   After terminal size is reached, energy demand declines to maintenance alone, and resembles that of the adults feeding schedule.  It has been said that parents will disallow food for a few days around this age to encourage fledge, however some researchers state that this is not true, and the eaglets fledge when they feel confident in doing so.

[pelmomma]

The wings of an eagle are approximately 6 to 7 feet from tip to tip fully stretched.

The pectoralis major muscles and the supracoracoideus muscles beneath them account for between one-fifth and one-third of the total body weight.  These muscles are the primary engines of bird flight.  Birds use their strong breast muscles to flap their wings and give them the thrust to move through the air and fly.

Eagles have a greater amount of wing loading (the weight carried by the surface area of the wings) than most other birds.  Adult wing loads are about 15% greater than those of young eagles.  This is because adults weigh more, and their wings are narrower.  Immature eagles, with their relatively larger wings, flap slower than adults.  That changes progressively as an eagle ages.  Adult wings are adapted for speed and attacking, whereas the wings of young eagles are adapted for soaring and lift.
 

[pyrmum1]

The position of the eagles' eyes allows both monocular vision where both eyes operate somewhat independently to see objects to the side, and binocular vision, where, like those of humans, both eyes focus on an object directly in front of the head.  Binocular vision gives them extremely accurate depth perception and allows for precise depth of field - an important asset for a bird that has to pinpoint prey from great distances in order to snatch it with their talons. In addition, their eyes have two fovea, or pits or funnel-like spots on each retina that are the points of sharpest vision.  One faces forward and the other is directed sideways enhancing their vision. 

[smileawhile]

Occasionally we see DH2 sporting some fuzzy “bling” on the beak. That is simply some of the remaining white natal down. Most of the natal down is gone but Dr. Scott Nielsen in A Season with Eagles reminds us that during the last two or three weeks (or days?) before an eaglet fledges s/he will spend time preening out the last of the  down, in the process inadvertently indulging in a little self-decoration.




[Bob1603]

NEST-VISITING ETIQUETTE
Federal guidelines mandate that humans stay 330 feet away from nesting bald eagles and individual eagles who may be perched on a tree or standing on the ground. That being said, it is
important to stay as quiet as possible, move slowly, and do nothing that might stress the birds. Do not feed the eagles and keep the area free from litter. This includes leaving food on the
ground. These birds are wild and should not become dependent on humans. Do not approach the eagle if it is on the ground, and don’t attempt to follow it if it flies away. Respect landowners and do not trespass.

Disturbance of nesting eagles can vary from minor to major and is defined as anything that might change an eagle's behavior. If it stops what it is doing (preening or feeding its young for example) that is a sign it has been disturbed. Eagles seem to be most alarmed by visual disturbances. Providing a visual buffer works well while observing eagles. Cars make excellent blinds. Major disturbances may cause the birds to abandon their nest or cause young eaglets to flush from the nest before they are ready to fly. While some eagles may seem to be habituated to human activity, it is unknown what the cumulative effect of minor disturbances might have over time.

In Just Eagles, Alan Hutchinson published the very helpful North American Nature Photography Association’s “Principles of Ethical Field Practices” that give suggestions on how people can
enjoy nature in a way that protects the animals and environment in which they live. Binoculars and/or cameras will afford you the best view while visiting a nest.

[Iriscats]

FLIGHT
An adult bald eagle flies (cruising speed) at approximately 30-35 miles per hour and can dive at a speed pf up to 100 miles per hour. Measured flight speeds of migrating eagles were recorded at between 36-44 mph (Broun and Goodwin 1943) In flight, they can reach an altitude of some 10,000 feet.

When a bald eagle soars, it rides upwelling warm air currents or thermals; in so doing,
it uses minimal energy of its own. Bald eagles also utilize obstruction currents, which are produced when wind currents are deflected by mountains, cliffs or tall structures.

There are three flight patterns used by adult bald eagles: 1) ascending in a thermal, then gliding downward which can take them several miles before they need to find another thermal: 2) circling steadily downward using a "street of thermals," which is a series of rising air masses that often result from a single strong thermal: 3) using rising air currents generated when winds sweep against a cliff or other raised feature of the local terrain.

[tulsaducati]

Feathers of the wing and tail of fledglings are longer than those of adults, but it still takes approximately five weeks from fledge to fully form flight feathers, develop muscle strength and improve flying skills.  According to Gary Bortolotti in The Bald Eagle, juvenile primary feathers are about 8% longer than adult, secondary about 13% longer and tail feathers about 23% longer.  As an eagle matures, its wings become shorter and narrower and its tail shorter with each successive molt.  The theory is that the fledglings’ greater wing area makes it easier for them to be carried aloft in a thermal or updraft.  It also allows them to fly slower and to soar in tighter circles for smaller thermals than the more experienced adult eagle. 

[tulsaducati]

After the eaglet leaves the nest, she/he will begin to hone flying skills and landing techniques, and begin the process of learning to find and kill prey.  They will still depend on the parents for food for several weeks.  That dependency will gradually diminish as they learn to forage.  Because fledglings are poor hunters, they will likely scavenge on carrion for a time.   Eaglets typically stay close to the nest tree during the first few weeks after fledging, but they eventually begin to explore areas further away.  Scott Nielsen states that up to five weeks is required from the time the eaglets leave the nest until their flight feathers are completely formed.  This period is used not only to complete feather growth, but also to develop muscle strength and improve flying skills.

[glogdog]

Young eagles learn by watching their parents, and by practicing instinctive behaviors.  Juvenile skills are perfected by trial and error.  Within about a month after fledge, they will have mastered the art of soaring.  By late summer, these 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, traveling irregularly and unpredictably.  Until then, they generally stay within a mile or so of their natal nest.  Mark Stalmaster tells us that through their 20th week, seven weeks after fledging, most young are still within approximately .9 miles of the nest.

[pelmomma]

Mark Stalmaster, in The Bald Eagle, explains that “approximately 6-10 weeks after fledging, when they are 17-23 weeks old, the young eagles begin to break family ties and leave the nesting area.   It is a time to migrate south if their natal nest is up North, or a time to go north if they are raised in the southern latitudes.  In some populations that are not migratory, the young may remain in the vicinity of the nest for several years.”

[Bob1603]

The Decorah area is located in what is called The Driftless.  The video below delivers extremely rare footage of natural phenomena and scenic beauty in the Driftless in a way never seen before.  Please note that one of people involved in producing this video is a brother to RRP director John Howe, George Howe.

https://www.imdb.com/title/tt9009474/