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[jfrancl]

It's been a busy week in Decorah! We ave much to celebrate! All 3 eaglets have branch and so far D34 has fledged!

Today, Saturday, we are holding our annual First to Fledge Fundraiser in honor of D34! Please join us for a day of fun and giving. Without your generous donations, this would not be possible so please help us support RRP's mission and Bob Anderson's dream! Join us here during normal chat hours. https://www.raptorresource.org/birdcams/decorah-eagles/

[eaglesrock29]

D34 and D35 are 11 weeks old today and both have now fledged (D34 at 74 days and D35 at 77 days).  D36 is 74 days old today and looks to be quite ready to go as well, making his or her way around the nest tree with confidence.*

So what can we expect to see as the eaglets are entering their 12th week?  For one thing, we will see much less of them around the nest area, which is sad for eagle watchers and amazing for the eaglets. 

Once fledged, the juveniles will begin to hone their flying skills and landing techniques, and also begin the process of learning to find and kill prey.  They will still depend on their parents for food until they are self-sufficient, which will take at least several weeks.  Their dependency diminishes as they learn to forage.  After fledge, young eagles will chase their parents to claim prey, which may be delivered at the nest or elsewhere.  Look for increased competition and aggressive behavior (good eagle table manners) among the eaglets to claim and steal prey. 

Eaglets typically stay close to the nest tree for several weeks after fledging, but they eventually begin to explore areas further away. 

Their flight feathers are still developing further.  Researcher Scott Nielsen stated that it may take up to five weeks after fledge 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.

The young eagles will learn and hone their skills by watching their parents, and by practicing instinctive behaviors.

*P.S.  As of the initial writing, D36 had not fledged but has since fledged today as of 6:09 pm, tying sibling D34 and Mom's previous offspring D20, D24 and D28, for earliest Decorah fledge at 74 days. 

[tulsaducati]

After the eaglets leave the nest, they will begin to hone their 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.

[jfrancl]

For 6/23/20

From RRP 6/22/2020:

If you are in Decorah, don't chase the eagles and be sure to give them a little room. Chasing is not only illegal, it can harm the eaglets since it interferes with their ability to get food and rest and stresses them out. Acute stress can kill birds. We have a guide to Eagle Etiquette here: https: https://www.raptorresource.org/wordpress/wp-content/uploads/2018/04/BALDEAGLENESTETIQUETTE.pdf

6/23/2020:

Amy went down to Decorah yesterday to take a look around for the eaglets (and tell people not to chase them). Everything was soaking wet and the hatchery was surprisingly empty, but she did manage to find two eaglets! Our camera operators and mods identified them as D34 and D35. These photos are not great - they were taken with a phone, from a distance, so as not to disturb the eaglets - but they give us a glimpse! Our camera operators also found the eaglets: https://youtu.be/odbTKBaIAzg and https://youtu.be/1gUinOGi92Q for two very nice looks!

Brett visited and searched as well. He wrote: "We saw one adult in the maple for hours and found one immature in a snag directly across the creek from the nest. The adult from the maple flew over near the nest and perched (that bird was SOAKED!) and the two talked a bit. We saw no more flights and left shortly after that. We walked the path near the nest and the surrounding areas searching for other fledglings but found none. The rain was coming down steadily. I think it was good that only the adult flew ? not the conditions you want inexperienced fliers in."

Are the eaglets still getting fed? Mom and DM2 delivered three fish just this morning. Everything was so drizzly wet yesterday that the eagles spent most of their time perching and drying off. John and Neil will be at and around the hatchery today, which looks a lot nicer for Outdoor School!


Here is a Time Table for Nesting Bald Eagles and their sensitivity to human activities near the nest that I have saved: https://www.fws.gov/midwest/eagle/permits/baea_nhstry_snstvty.html

Audubon Center for Birds of Prey human activity and disturbances near an active nest: https://cbop.audubon.org/conservation/human-activity-and-disturbances-near-active-bald-eagle-nests

Young fledglings need space to learn all that they need to know to be self sufficient. We can help by abiding by these guidelines when visiting this nest or any other bald eagle nest.

[tulsaducati]

First year bald eagles are notorious for attacking just about anything that floats or moves. 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.  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.

[eaglesrock29]

We've talked often in chat about imprinting and there are several previous Facts of the Day that discuss the five parts of imprinting, the last of which is imprinting on nest type, style, and habitat.

Biologist Nick Fox stated that birds will imprint on their immediate surroundings, such as type of nest -- e.g. sticks, rock cavity, ground.  Once the bird is flying, it will imprint on larger aspects of the nest -- e.g. the nest tree, cliff, or man-made structure -- and the surrounding habitat.  In his book, Understanding The Bird of Prey, Fox states "There is a strong correlation between the type of nest in which chicks grow up and the type they will subsequently choose as adults." 

When juveniles leave the nesting territory for the first time, it is thought that they will imprint on land forms such as rivers and cliffs.  This is apparently at least in part how many eagles are able to find their way back to the territory from which they fledged. 

Research shows that female birds tend to disperse further than males.  The tendency for many bird species to return to breed for the first time in the general area of their natal territory is called "fidelity to the nest."   Recent research suggests that males generally begin nesting within 38 miles of their natal nest, while for females, the distance is within 88 miles.

[oregonian1944]

What do we know about bald eagle flight?
They fly at approx. 30-35 mph and can dive up to 100 mph. In flight they can reach an altitude of approx. 10,000 feet.  When they soar, they are riding warm air currents (thermals) and use very little energy to do that.

They have 3 flight patterns: ascending in a thermal, which enables them to soar for several miles before they need to find another thermal; circling downward using a "street of thermals" (series of rising air masses) that results in a single strong thermal; and rising air currents that happen when winds sweep against a cliff or other raised feature of the local terrain.

[jfrancl]

Dispersal:

Mark Stalmaster stated that approximately six to ten weeks after fledging young eaglets will begin to break family ties and leave the nesting area.  Dispersal times vary depending on the individual bird, some leaving sooner, some later. By this time they are more or less sufficient, able to fly with ease and acquire prey on their own.  In some populations that are not migratory, they may remain in the vicinity for several years.  And even migratory juveniles may return to the general area of their natal nest location, and perhaps establish a territory of their own and continue the cycle of breeding.  Colder weather increases eagles food requirements and shorter days give them less time to obtain sufficient food. In addition to learning hunting techniques the juvenile will learn what type of prey to hunt and what not to pursue though some prey recognition is obtained while in the nest. First year eagles are notorious for attacking just about anything that floats or moves.  Whether they are successful or not in capturing prey is a different story.  Most first year eagles will feast mainly on carrion or stealing prey from other eagles and other species of birds.

[Iriscats]

FOD for June 28,2020

Fishing

Bald eagles use a number of techniques to search for and catch prey.  When a fish is sighted, the eagle will usually descend quickly and smoothly from its perch. The eagle starts at a high angle and has an idea of the location of the fish.  As it gets closer to the fish, 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 big fish) descend to scoop  up the fish and carry it off. Occasionally when capturing 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 ashore swimming awkwardly, stroking the surface of the water with its wings while pulling with its talons to shore.  Another less common technique is wading in shallow water where smaller fish are available.  According to Stalmaster, an eagle will wade up to its belly, submerge its head, and strike with its beak.

Eagles more easily recognize and catch a fish that is upside down (white side up), than right side up(darker side up).  White side up are more quickly spotted and caught. Apparently to eagles' eyes, the white belly is more visible than the darker back.

Bald eagles have a tendency towards species of fish that inhabit shallow water or are surface feeders and therefore vulnerable.  Young eagles are much more likely to "catch" fish that have washed up on shore or fish that are floating rather than swimming.

One study found that when eagles attempt to steal prey from other birds they are successful about 55% of the time.   

[smileawhile]

FOD for June 29 2020

It can be a real challenge to ID eagles by plumage from their first through fourth years.
There can be variations in the mottled plumage as a result of:
     incomplete molts
     sunlight fading the feathers
     fading of older feathers
Mark Stalmaster, in 'The Bald Eagle', states that some eagles might skip a plumage class, or retain
one for a longer period, so that many features can be in flux and do not fit any one pattern.
Some researchers think the least pattern variation can be found in the head plumage.
Head color progression (generally):
     1st year - Dark Brown to Brown
     2nd year - Brown to Light Brown
     3rd year - Gray and Light Brown
and by the end of the 3rd year the eagle will sport the "osprey" look of dirty white head with dark
eye stripe.  At this point the tail will also be a dirty white, with possibly a dark terminal band.

While the Decorah nest is inactive or the cameras are shut down for maintenance, I highly recommend that you meander over to the RRP Mississippi Flyway cam (home page - link under 'Watch Birds' tab). You will see eagles of every age hunting, feeding, stealing and interacting with each other.

https://www.raptorresource.org/birdcams/flyway-cam/

https://www.allaboutbirds.org/guide/Bald_Eagle/media-browser


Sources:
    Stalmaster, Mark    The Bald Eagle
    Nielsen, Dr. Scott    A Season with Eagles
    Gerrad/Bortolotti    The Bald Eagle  Haunts and Habitats of a Wilderness Monarch

[glogdog]

Tails are integral to bird flight and are comparable to the rudders of ships and boats.  They help birds steer and maneuver while flying, as well as provide stability as they take-off and land.  By twisting its tail, the bird can change its direction mid-flight.  To help the bird slow down, the tail flares out downward, creating more drag and decreasing the bird's velocity.  While the bird is soaring, it can spread out its tail feathers behind it to create additional lift and stability. 

There are 12 tail feathers, formally called rectrices or retrices.  They measure between 11-16 inches in length.  The two center tail feathers are called Deck feathers because they are slightly raised. To minimize flying problems, wing and tail feathers usually molt symmetrically so that matching feathers from the right and left sides fall out at approximately the same time.

[tulsaducati]

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.  Frank Gill states that large natal dispersal distances can unite populations while small natal dispersal distances may enhance genetic isolation.  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.

[jfrancl]

July 3, 2020


For our final Bald Eagle Fact of the Day post in the forum, I'd like to recommend some birds of prey books for you to read while chat is closed. I hope this makes the time go faster for you and that you enjoy reading them as much as I did.

Hawks, Eagles and Falcons of North America by Paul A. Johnsgard

Majestic Eagles by Stan Tekiela

Raptors the Birds of Prey by Scot Weidensaul

Just Eagles by Alan Hutchinson and Bill Silliker Jr.

How Fast can a Falcon Dive? by Peter Capainolo and Carol A. Butler

A Season with Eagles by Dr. Scott Nielsen

Understanding the Bird of Prey by Nick Fox

The Bald Eagle by Mark Slalmaster

The Bald Eagle Haunts and Habits of a Wilderness Monarch by Jon M. Girrard snd Gary R. Bortolotti