THE DECORAH EAGLE DICTION-AERIE AND ALPHA CODES

This topic is a combination of numerous codes and explanations guaranteed to assist you in viewing or discussing the eagles.

With Eggstraordinary Graditude to chatters, and many other EAs who contributed to our eggspanding vocabulary of Eagle-ese / Eaglish we proudly present the Decorah Eagles Diction-Aerie for you to print out, mantle over, and devour the knowledge presented by the Fledge-U-Ating Eagle 101 Class of 2011. (Original post on Facebook by Sherri Elliott)

The Diction-Aerie
Air-obics - Extending wings and catching a bit of air.
Anthropmorphism - projecting human characteristics onto animals.
Apteria - area on breast with no feathers; aka -brood patch.
Balloon Mantle – a puffball of feathers exhibited by E3.
Beak Geeks - people that are avidly watching them daily.
Beak Lips – area of beak sides to corner of mouth.
Beakering – sibling disagreements.
Beakoff - eaglets fake fighting with their beaks.
Bedreagled Eaglets – raggedy look after bad weather.
Bird Nerds – people that are avidly watching them daily.
Bling – unidentified accoutrements brought to the nest from Nest Depot - usually brightly colored.
Branch Office – Mom & Dad spend most of their time in this space adjoining nest after eaglets grow into juvies.
Branching - eaglets hopping from one branch to another prior to fledging.
Breakfish – first meal of the day.
Cameritisi Permanentitis Bugitis – bug on camera lens, also known as camera bugs.
Cere – fleshy, membranous covering of the base of the upper mandible.
Claw Floss – name given to Pinky, the baling twine.
Cleaning Coma – behavior emulating Dad’s cleaning skills, but generally tiring quickly, lapsing into face plant.
Clown Clomp – comical eaglet first steps learning how to walk.
Clown Feet - oversized feet/talons that the eaglets haven't grown into yet, nor know what to do with.
Convocation – group of eagles in tree or on ground.
Corn Husk – outer dried corn covering coveted in nest.
Corn Husk Pillow – said item used as head rest.
Corn Stalk – building material for nest crib rails.
Clutch – number of eggs laid in a nest.
Crop - area in neck where food gathers first before entering stomach if it is full.
Crop rotation - food moving from the crop to the stomach for digestion (and filling up again).
Cuddle Huddle - all the e's close together for safety/warmth in a group.
Cuddle Puddle – horizontal E cuddle sprawl.
Decorah - the idyllic location in Iowa where our family set up its Home-Tweet-Home
Decorah Drop – nap flop.
Decorah Front Porch – our place to watch the EEeee's.
Decorah Shimmy - back and forth motion that Mom/Dad use to position themselves over the eggs/eaglets.
Decorahating – beautification of the nest.
EA'S - Eagle Addicts, aka: Eagle-holics.
E-ddicts – those who watch eaglets and stay in pajamas all day.
E-Gulp - swallowing food whole.
E-Heap – pile of eaglets.
E-Lump - same as cuddle huddle.
E-Pology - Submission bow or another act of 'sorry' after a sibling altercation.
E-Team – long suffering worrywarts who love eaglets.
Eagle Condo – eagles in penthouse, smaller birds in lower stories.
Eagle Kneivel – daredevil or showoff behavior.
Eagle Time – no time that has anything to do with human time.
Eagleholics Anonymous – 12 step recovery program for eagle addiction..
Eagleholics - (Eagle-holics) people that are avidly watching them daily.
Eaglestock/Eaglefest - 206+ million viewers united on web cam broadcast.
Eagle-ese – our unique vocabulary, also known as Eaglish.
Eagleibrium – balance achieved only by eagle walking.
Eaglemaniacs – people who eat, drink and sleep eagles, with not much real sleep actually occurring.
Eagleicious Delicious – any delightful E behavior.
Eagletecture – construction skills used by Dad to create the nest.
Eaglish - all the words we made up for this dictionary.
Eagulp – swallowing food whole.
Ealergies – involuntary sneezing reaction.
Eyas stage - fresh from nest
Face Plant - off balance eaglet plopping into nest face first, perhaps going into food coma.
Feaking - cleaning a beak.
Feathairdresser – wind redecorating Mom’s hair.
Featherline – e’s hairline feather growth giving them distinguishable identifiers.
Fish Fledge – result of food fight when intended meal accidently goes off the nestbowl.
Fishereagle – Dad, Dad, Dad.
Flappathon – endurance contest of e’s getting pumped up.
Fledge – taking the leap from branches to the air of the big beyond.
Fledge Fest – gathering of EA’s making road trips to witness fledging.
Fly-By – parent checking in, but not landing, and with or without food.
Fly-By-Fake-Out - parent flying by with food to lure E's out of nest.
Flying monkeys – teenlets similarity when wingersizing to the Wizard of Oz flying army. Hum the song: oh weeee oh...ohhhh oh when seeing this behavior.
Food Coma - state of suspension E's go into after eating too much.
Fret of chatters - a group of chatters worried about the eagles.
Flapadoodle: Amusing flurry of wing flaps performed by Mom, sometimes Dad, while sitting (incubating) the eggs. Generally occurs in middle of night and scares the heck out of everyone watching.
Flapping Jacks - eaglets exercizing their wings.
Fledge-U-Ation – eaglets graduate to fledging.
Fritching - itching new emerging feathers.
Gnat – larger than noseeums and especially fond of the eagle's head area resulting in eagle neck jerk twitching.
Gnat Gnat – a term of endearment used interchangingely for nite nite by EAs.
Gnat Scat Boogie – the e’s headtwich dance.
Guy-liner – one way to identify Dad is black liner around his eyes.
Hallux – rear locking talon, also known as eagle thumb.
Hard Penned – feathers firmly attached to bone.
Hoppersizing – up and down movement, usually in conjunction with wingersizing.
Hop-Squash – exhuberent nest hop resulting in a sibling step on. Usually E2 gets hop-squashed.
Hoppiness – what else would you do after a good feed and found you had wings? Happy-Hop!
Hover Mantle – mantling behavior parallel to the prey of the day.
Hovering – catching air with outspread wings while staying in a fluttering suspended motion.
Hugbrella – wingstretch from one e to another.
Kettle - group of eagles in the air.
Juvie sprawl – juveniles taking up extra nest space spreading wings out while napping.
Leap Eagle – hopping over a sibling.
LEGO Eagle – pixilated image of our eagles.
Lumpasizing - E's staying close together or sleeping in a pile.
M.O.D.S – Master Ornithological Data Searchers; also gatekeepers of the RRP FB page or chat.
Mantle - The action of a bird spreading its wings, fanning the tail & arching over prey, to hide it from other predators, including other birds or siblings. From Old English/Norse for cloak. (E3 delighted us with several distinct mantles: Balloon Mantle and Ninja Mantle).
Master Mantler – E3 showed extraordinary mantle diversity.
nest depot - nearby areas where corn husks, branches, horse hair, or nesting material is available.
Moist Fowlettes – wet eaglets.
Mombrella – Mom covering her eaglets with her wings, mostly in inclimate weather. (see also poptent).
Moonwalk – backup walk prior to a poop shoot.
Muskrat jerky – poor thing which gets picked on by the e’s w qhen unearthed from the nest.
Nare – nostril holes on the beak.
Nest Depot – wherever Mom & Dad can find new décor for the nest; ie- horsehair, corn husks, branches, straw.
Nest guests – anyone watching the UStream video.
Nest Potatoes – eagles lazily lounging, usually after eating.
Nestication – staying put in nest or branches; too relaxed to pack and fly off.
Nestogarbage – nest garbage or debris.
Nestoration - The act of rearranging or redecorating the nest
Nestovers – uneaten food found in the nest.
Netiquette – a level of decorum expected on Decorah’s RRP Facebook page.
Nictitating Membrane – transparent inner eyelid, also known as the third eyelid protecting the eye.
Numb Butt – affliction caused by sitting at the computer too long.
Ninja Mantle – heightened Zen-Like state of mantle & hover (first exhibited by E3 on 5-29-11)
Obstacle Occlusion – varying perspectives of the reality of the nest.
Outstinkt - eaglets knowing instinctively to PS out of the nest.
Owl – urban legendary creature purported tohave attacked eagle nest; totally mythical.
Pffffftt! – the distinct sound coming from a PS.
PS - poop shoot - evacuation of the bowels.
Pancake – flat eagle in sleeping position.
Pet Pillow - using your sibling as something to rest a part of your body on.
Pinky – name given to pink/red bailing twine brought into the nest, that inadvertently wound around E2’s foot.
Piscivore - fish eater.
Poop Art - original whitewash gouache on the nearby trees; a takeoff of the 1960’s Pop Art Movement.
Poopcassio - PS artist.
Poptent - Dad standing over the chicks with wings spread keeping them safe from snow/rain/wind or predator.
Porch Peeps - The E's adoring EA's who sit on an evereggspanding porch overlooking the beloved cottonwood tree to pay homage to our eagles.
Post D-Epartum Depression – condition to what will happen to EA’s when eagles leave the nest.
Predicure - manicure for a predator.
Prey Buffet - whatever the parents happened to bring for dinner.
Prey Toy – meal tidbit used as plaything.
PSFS – print screen finger syndrome synonymous with copy, print and save web stream photo captures.
RWS - restless wing syndrome.
Ramage - true feathers coming in.
Raptor – a bird of prey, regal in the birddom. (Latin, one who seizes, from rapere).
Reversed Sexual Dimorphism – the female eagle is generally bigger than the male – opposite of other species.
Rictus - wide open mouth.
Screech-fest - sound associated with food fest.
Screagling – screeches made by e’s.
Screeeeeeee – typed sound the e’s make in one or multiple vocalizations; can interchange with squeeeeee.
Screaching – sound associated with food frenzy.
Separation eagxiety – the anxiety tht the last eaglet feels when it is left in the nest alone, sans siblings.
Shaking Juvie Syndrome – trying to get the gnats off ones head by shaking it.
Spicules – the rear talon.
Sprawled Eagle – eaglet sleeping with wings spread covering a larger mass area than spread eagle.
Spread Eagle - eaglet sleeping with wings spread (see also sprawled eagle).
Squabbit – what we call the newest furry snack when we can’t figure out if it is a squirrel or a wabbit.
StarBeaks – EA’s favorite corporate cawfee. Most popular blends: Decorah Decaf and Mocha Mantle.
Sub-Adult - juvenile eagle.
Sweagle Dreams – sweet eagle dreams.
Syrinx – flap between esophagus and lungs that eagles make vocalization sounds.
Tail Wiggle-Waggle – movement of the eaglets tail after they realized they had one.
Tarsus – the section of vertebrate foot between the leg and metarsus.
Tippytalon – eaglets doing the ballerina thing.
Tweagles – juvenile teen eagles.
Tween Preen – Eaglets in their ‘awkward’ phase trying to get their feathers unfurled.
Twiggs - playing with branches like Lincoln logs.
Twittering - calls made by young eaglets.
U.I.A. – unidentified animal brought in as prey.
Whatta - The best way to start a sentence!
Wilson – name given to the beloved cornhusk that resembled the volleyball in the film “Castaway”.
Windteruption - high wind day that causes the e's to lay low.
Wingercizing - excercizing the wings.
Wingpits – self explanatory.
Wing Smackdown – exhuberent wingersizing between two or more eagles resulting in a takedown.
Wing Whack - one eaglet stretching his wing while laying down and hitting his/her nearby sibling with it.
Wonderstruck - The overwhelming feeling produced by the EEeee's.

Alpha Codes
A = Ant
AD = Additive
B = Bugs
BB = Beak Biting
BH = Branch
BFP = Big Front Porch
BG = Beak Geeks
C = Cat
CA = Camera
CH = Cornhusk
CHP = Corn Husk Pillow
CL = Clutch
CP = Crop
CS = Cornstalk
CT = Cottonwood
D = Dad, Daddy
D1 = Dog (This was prior to D1, being named D1)
DE = Decorah
E = Eagle or Eagles (1,2,3)
EA = Eagleholics Anonymous
EG = Egg
EPU = Eagle Parental Unit
E101 = Eagleholics 101
E-lumni = Eagleholics 101 Graduates
F = Fledglings
FS = Fish
FC = Food Chain
FP = Faceplant
G = Gnats
GR = Grunt
H = Horse
H1 = Human 1, Human 2 (at farmhouse)
HA = Hatchery
HC = Hatch
HV = Hovering
I = Icing On The Lens
IB = Incubate
IA = Iowa
IF = Infrared
J = Juvies
JK = Jerky
K = Kleenex
KU = Kudos
L = Leaves
LT = Light
LV = Love
LE = Lens
M = Mom, Mommy
M1 = Mod
M2 = Mod II
M3 = Mod III
MB = Mombrella
MK = Muskrat
MT = Mantle
N = Nest
NIC = Nictitating
NS = Nestorations
O = Owl
P = Parent(s)
PA = Panning
PCH = Porch
PCP = Porch Peeps
PE = Pellet
Pfffft = Poop shoot sound
PX = Pixels
PR = Preen
PS = Poop Shoot
PT = Poptent
PTZ = Pan, Tilt, Zoom
Q = Quiz
R = Rabbit
RF = Raptorfan81
RRP = Raptor Resource Project
S = Stream
SA = Separation anxiety
SN = Snow
T = Tree
TA = Talon
TF = They're Fine
U = Unconditional Parent Love
UFO = UFO
UST = UStream
UV = Ultraviolet light
V = Victory Of The Fledge
VB = Victory Branch
VE = Venison
W = Wilson
WGZ = Wingersizing
WI = Wind
X = Xtra Knowledge
XO = Kisses & Hugs
Y = Branch
Z = Zoom
ZS = Zzzzzzzzzz's

Special Additions:

eeeeeeeeeeeeeeeee = E1
eeeee eeeee eeeee x infinity = E2
eeeee eeeee eeeee (3x) = E3 (and with a grunt, eating)

Happy watching!

Peregrine Falcon FAQ

While we wait for eggs to hatch in Decorah, Valmont, and Fort St. Vrain, I thought I would talk a little bit about Peregrine falcons. Prior to the Decorah Bald eagle cam, Peregrine falcon recovery was what we were known for, to the extent we were known at all.

In Flight
The Peregrine is the fastest animal in the world, diving or stooping at speeds that can reach over 200 miles per hour. Almost everything about it is built for speed, from the baffles in its nose  to the jagged edges of its slim, stiff feathers and long, pointed wings.

The falcon catches other birds in flight by diving on them from above.  As she begins her stoop, she rolls, cups her wings around her body, and tucks in her feet. This change in shape streamlines her profile, yielding an aerodynamic raindrop that can cut through the air at high speeds.

Photo used with permission of Karen Carroll, http://www.birdsofprey.net

As she plummets her nictitating membrane, a transparent 'third eyelid', protects her eyes from dust and debris in the air and a secretory gland helps keep her corneas from drying up. A special cone or baffle in her nose regulates the amount of air entering her nasal cavity, allowing her to breathe and protecting her from damage. A curved flight path keeps her prey in view and reduces her aerodynamic drag. Before she strikes her prey, she'll experience G-Forces estimated at between 25-27 Gs.

The Peregrine meets her prey feet-first. She slows first, unfurling her wings and tail, and dropping her feet. After striking and stunning or killing it outright, she'll loop around in mid-air to retrieve it and take it to a safe place for plucking and eating.  

Falcon Belinda at Xcel Energy's Allen S. King plant aims at a reporter.

Lifestyles of the Fast and Furious
Falcons are roughly crow-sized. Females are about a third larger than males, although they both have bluish to slate grey backs,  barred or streaked white to rusty underparts, and a black hood. Adults have black beaks and yellow feet, although their babies may initially have bluish feet.  This is natural and not a cause for alarm.

Both males and females are highly territorial. Like eagles, Peregrine falcons are relatively monogamous (polygamy has been documented, but isn't common) and may or may not migrate. Unlike eagles, they are relatively solitary birds.

Traditionally, Peregrine falcons nest on cliffs, laying their eggs directly on a scrape they created in a gravel or sandy substrate.  In the midwest, Peregrine falcons generally:

• Lay eggs in late March or early April
• Hatch in late April to early May, or 33 days after the first egg is laid.
• Begin flying in mid-June or later, or about 40 days after hatch.

Peregrines make excellent, attentive parents. The babies cannot thermoregulate (control their temperature) until they are about 10 days old, so Mom spends a great deal of time huddling over them while Dad feeds everyone. As the babies age, both parents spend time hunting. The eyrie is small and the babies, which have among the fastest growth rates in the animal kingdom, are large and hungry. They eat, sleep, poop, and go from white fuzzballs to sleek brown juveniles in about five weeks.

Once they begin flying, the young peregrines spend a lot of learning how to fly and hunt: something that looks a lot like play to most human observers. Their parents will continue to provide some food for their newly fledged young who are not yet self-sufficient.  Come fall, the adults may or may not migrate, but their children will disperse. In our experience, the young falcons tend to leave in September. Once they are gone, they are gone. If they do come back to the nest, their parents will defend it from them. 

What to expect when falcons are expecting
The new Great Spirit Bluff nest cam wonderfully documented falcon courtship. The falcons engaged in  ledge displays on the roof of the nest box, bowing and calling loudly.


As courtship progressed he made a scrape, digging into the gravel with his breast and pushing with his legs to create a depression (males and females will do this - our video shows the male).


Finally, both falcons bowed and e-chupped over the scrape.


The male also courts the female with food. Our video shows him bringing it to the nest box, but falcons also transfer prey midair. There seems to be a little bit of food fight here as well, but think some courtship was going on.


She will probably lay three to four reddish speckled eggs sometime in March. Peregrine falcons do not begin full incubation until after egg number three is laid, so it is normal for her to spend time - even quite a bit of time, depending on how warm it is - away from eggs number one and two. Her eggs should begin hatching 33 days after the third egg is laid.

Mae's eggs, Xcel Energy Allen S. King Plant.
Some egg color variation is normal.

During incubation, she will experience hormonal changes that help keep her incubating. She may appear sleepy or lethargic, and will spend a lot of time picking at gravel and sitting more or less quietly on her eggs. She does most of the incubation, although the male will spell her briefly. The male is smaller and may have a harder time covering all of the eggs, depending how many are laid. We can also expect to see egg rolling (Brent, at the Allen S. King plant, is well-known for this) and some shimmying. This is not a particularly active time for the falcons: I've heard Bob refer to incubation as the 'egg doldrums'.

My reference list:

• Bob  Anderson
• Video makers razzle and chico70
• http://blogs.bu.edu/biolocomotion/2011/12/12/why-can-the-peregrine-falcon-fly-so-fast/
  (peregrine falcon and speed)
• http://blogs.bu.edu/biolocomotion/2011/10/07/the-fastest-animal-on-earth-the-peregrine-falcon/
  (peregrine falcon and speed)
  http://jeb.biologists.org/content/203/24/3755.abstract (curved flight plans and sideways vision)
  http://www.dvrconline.org/raptoradapt.html (raptor adaptations)
  http://www.airspacemag.com/flight-today/falcon.html (Falling with the peregrine falcon)
  http://www2.ucsc.edu/scpbrg/pefabehavior.htm (pefa behavior)

Eggs!

We are getting a lot of questions about eggs and hatching.  It takes 35-37 days for Bald eagle eggs to hatch, 24-28 days for Canada goose eggs to hatch, and about 28 days for great horned owl eggs to hatch. Despite the differences in incubation times, very similar things happen in the eggs of all three species. 

What happens within the egg shortly before hatching starts?

The rapidly developing embryo...

• Grows large enough to take up nearly all the space.
• Positions its body so that its head is at the large end of the egg next to the air space.
• Begins to breathe with its lungs. Ever crack an egg and see the white membrane inside? Before the chick pokes its beak through this membrane into the air space, a special tissue called the CAM supplies oxygen to the developing embryo. Gases, including oxygen, leave and enter the egg by diffusing through the pores in its shell, across the outer and inner shell membranes, and into the blood in the capillaries of the CAM. From there, the blood circulates through the embryo and provides it with oxygen - no lungs required until the membrane is broken. 
• Consumes most of the remaining albumen and yolk. When I was young, I thought that birds formed from the yolk. Not so! The yolk provides food and energy for the embryo.

The chart below outlines major developmental points in the lifecycle of a developing chicken embryo. At 20 days, the chicken is almost large enough to break the membrane and begin hatching. The timing would be a little different in the case of Bald eagles, Canada geese, and Great Horned owls, but the stages of development are the same.

Successive changes in the position of the chick embryo and its embryonic membranes. (From A. L. Romanoff, Cornell Rural School Leaflet, September, 1939.) (Fig. 9). Website: http://chickscope.beckman.uiuc.edu/resources/egg_to_chick/development.html

So how do birds hatch?

The embryo has breached the membrane, is breathing air with its lungs, and is head up, with its head positioned at the large end of the shell.

• Our embryo  uses its egg tooth, a small temporary structure on the op of its beak, to cut through the shell from inside. The eggshell is thinner and weaker than when it was laid, since the growing embryo absorbed calcium from the shell for its bones. The embryo rubs its egg tooth against the shell, which cuts a small hole.
• As it rubs it rotates its body, slowly cutting a ring around the shell.
• When the cut is complete, the hatchling bird pushes its body against the shell, forcing it apart.  It works itself free of the shell membranes and halves. Viola - a baby bird!

Here is a time-lapse video of a chicken hatching. The hatchling pips, or makes a hole in the shell, and begins rotating.

Altricial versus precocial
Our hatchlings face very different challenges. Canada geese are precocial - that is, they are relatively mature and mobile from the moment of birth. Eagles and owls are altricial, which means the young are helpless and require parental care. Bald eagle and Great Horned owl parents bring food into the nest for their young, often caching or storing prey for later consumption. This means that eaglets and owlets don't need to leave the nest or procure food until they fledge. The young goslings leave the nest within 24 hours of hatching and do not return to it. While their parents continue to provide protection and care, the goslings feed themselves.

The precocial goslings are also able to thermoregulate right away, unlike the eaglets and owlets. altricial birds require their parents (or a parent) to apply warmth until their down feathers are developed enough to insulate them. The eagle parents and mother owl will spend a great deal of time huddling over their young after they have hatched.


Resources

The following resources helped me write and understand this:

• http://chickscope.beckman.uiuc.edu/resources/egg_to_chick/development.html (egg development)
• http://en.wikipedia.org/wiki/Altricial (altricial birds)
• http://en.wikipedia.org/wiki/Precocial (precocial birds)
• http://www.unt.edu/honors/eaglefeather/2007_Issue/dzialowski4.shtml (CAM, respiration)

Things are getting busy! Here is a recap of all the action going on at our various nests. Remember, the estimates are estimates only - hatch could begin a little sooner or a little later at any location.

Valmont Great Horned Owls
We anticipated hatch would start on  03/10/12, but regular cam watchers think it may come a little sooner. The Valmont Owl fans are very dedicated and worth listening to, so you may want to check this one out sooner rather than later. Cam link: http://www.farmyou.com/falcon_cams/index.html and click the Valmont Owls link in the list on the left.

EagleCrest Canada Geese
This site has been full of surprises. The hawks have made a nest elsewhere, leaving an open nest tray for...geese? The Canada geese nesting here have laid five or six eggs despite an owl scare. We estimated hatch starting on 03/21/12. To watch EagleCrest's Wild Kingdom, follow this link:
http://www.ustream.tv/eaglecresthawks

Fort St. Vrain Bald Eagles
The Colorado Bald eagles laid eggs a little earlier than the Decorah pair, but I don't know what I was thinking when I estimated the 24th. I am estimating March 21 here. Remember, this is an estimation only. Cam link: http://www.farmyou.com/falcon_cams/index.html and click the Xcel Fort St. Vrain Eaglecam link in the list on the left.

Decorah Bald Eagles
We are anticipating hatch will start somewhere between March 23 and March 25. Cam link: http://www.ustream.tv/decoraheagles

Great Spirit Bluff FalconsThe Great Spirit Bluff falcons have been seen copulating and making a scrape, so we anticipate the female will be laying eggs soon. We are trying very hard to get band numbers here - we believe the male is P/(something) but we aren't quite sure about the bottom character yet.

Other Cams and Nests

• Missouri Turkey Vultures: Waiting for them to come back
• Riverview Tower Peregrines: Waiting for them to come back
• Dairyland Power Alma and Genoa: Falcons are back in both locations
• Red Wing Grain: Falcons are back. A fight between three of them was witnessed by plant staff on March 7th.
• Hibbard Power plant: falcons are on the grounds. We are considering cleaning out the nest box here ourselves.
• Agri-Bunge, McGregor, IA: Falcons Bonnie and Clyde are back.

We'll keep you all posted as nests begin hatching. Since I don't like to leave without photos or a video, here is a video by Mick from Great Spirit Bluff this morning. This is the male falcon (the proper word is tiercel). The male is making a scrape in preperation for nesting.

How big is the Decorah Bald eagle nest?

Our moderators are often asked about the size and weight of the nest. The short (and very rough) answer? The nest is roughly 5 feet high by 6 feet wide at the bowl, and weighs about 1367 pounds.
This should give you about the right idea of its size, if not its shape.

So how do you know that?
We haven't measured or weighed the nest, but I can do some rough back-of-the envelope calculations that should come close. We are going to pretend that the nest is a neat cone shape, if only because it is closer to cone-shaped than to anything else. This photograph of Bob lying down in the nest was taken two or three years ago.

Bob is around six feet tall and the nest is a little bigger now than it was then, so I am going to go ahead and estimate it at 6.5 feet in diameter, which gives it a base radius of 3.25. The nest was roughly 4.5 feet high when I was up there in October, but the nest is irregularly shaped and the eagles have been working on it, so I am going to go ahead and estimate it at five feet high. Fortunately, this isn't rocket science! Estimations are acceptable.

The formula for calculating the volume of a cone is (1/3) * pi * radius2 * height. So, (.3333) * 3.1415 * 10.5625 * 5 = 55.3 Or you can just go to an online calculator. I checked my answer at http://www.cleavebooks.co.uk/scol/calcone.htm

Now that we have our volume, we need to think about what the nest is made out of. It is in a cottonwood tree, in a neighborhood with other cottonwood trees, maples, and oaks. We can therefore assume that some of the branches are cottonwood, some are maple, and some are oak. Cottonwood weighs about 28 pounds per cubic foot, oak weighs about 46 pounds per cubic foot, and maple weighs about 46 pounds per cubic foot. Since I can't tell which is which by looking at them, we'll take an average of the three, which equals 40 pounds per cubic foot. 40 * 55 yields an estimated weight of 2212 pounds, or a little over one ton.

Earlier today, I gave 2212 pounds as the final weight. Wrong! It was pointed out to me that the nest is not a cone of solid wood - the branches are woven together and it has spaces, albeit tightly packed ones. I cast around a bit for a way to determine this unmeasurable space and finally decided to use the fibonacci ratio of 61.8%. This number, which is also referred to as the golden ratio, or the golden mean, turns up quite a bit in natural series, especially ones that involve spirals. Don't believe me? Check this out: http://science.howstuffworks.com/environmental/life/evolution/fibonacci-nature1.htm

Once I factored in fibonacci, my final estimate becomes 1367 pounds. Still a creepy thing to think about when you are dangling 50 feet above the ground on a rope attached to cottonwood limbs above the nest.

How big are Mom and Dad?
We don't know for sure, since we haven't captured and measured them, but we estimate about 8-9 pounds for Dad and 11-12 pounds for Mom. Their wingspan is most likely between 6.5 and 7 feet.

So how do you know that?

Again, we don't know exactly. Bald eagles vary in size. Bald eagles in Florida are much smaller than those in Alaska, probably because being large helps animals retain heat in cold weather (check out Bergmann's rule: http://en.wikipedia.org/wiki/Bergmann%27s_rule). Iowa has cold winters, so our eagles should be on the larger end of the scale. According to wikipedia (http://en.wikipedia.org/wiki/Bald_Eagle):

• The bald eagle's body length varies from 28-40 inches (70-102 centimeters)
• The bald eagle's wingspan measures between 5.9 and 7.5 feet (1.8 and 2.3 meters)
• The bald eagle weighs between 5.5 and 15 pounds (2.5 and 7 kilograms)
• Females average 13 pounds (5.8 kg) and males average 9 pounds (4.1 kg)

Kay Neumann from SOAR (Save Our Avian Resources) has a lot of experience weighing and measuring bald eagles that come into her rehabilitation center. Although these eagles are often sick or injured, and so may be a little lighter than a healthier eagle, she said:

"Males are weighing in the 8 to 9 pound range, and females are in the ten and eleven pound range. I’ve heard the Raptor Center (Amy's note: the Raptor Center at the University of MN) say from 8 to 12 pounds, and that seems about right for our Iowa birds too. The record holder is a 14 pound female, but she may have been a Canadian bird. So there is quite a bit of a range – just like people, eagles come in different sizes.

It is a bit deceiving in that they look as big as a turkey – 20 pound birds. Turkeys are designed to wander around on the ground and look for seeds while eagles are designed to fly and so built quite differently. An eagle has hollow bones and feathers for strong but light construction - just like a plane."

How big are the eggs?

The eagle eggs are oval, white, and roughly the size of a tennis ball. The Center for Conservation Biology at the College of William and Mary has a wonderful post on this:

http://eaglenest.blogs.wm.edu/2011/03/04/what-size-are-bald-eagle-eggs/

Bald eagle eggs weigh about 4.2 - 4.5 ounces (120-130 grams) and range from 2.3 to 3.14 inches (6-8 centimeters). They are 1.96 to 2.3 inches (5-6 centimeters) wide. They are hard-shelled. Everyone knows that eggs can't get too cold, but they also can't get too hot. Cam watchers have noticed the eagles seeming to spend a little more time off the eggs this year. This may be in response to the (relatively) warm winter. For more about the eggs, check out this blog: http://raptorresource.blogspot.com/2012/02/we-have-first-decorah-eagle-egg-of-2012.html

How big an animal can a bald eagle kill? For instance, can a bald eagle kill a deer? How much weight of prey can a bald eagle carry to the nest?

We don't know the biggest animal that a bald eagle can kill, although I have some prey weight estimates based on animals we have seen them carry up to the nest. Golden and Harpy eagles kill large prey, including deer, but I have not been able to find a reliable report of a bald eagle killing an adult deer. In general, a Bald eagle won't kill you and carry you away if you weigh over about 4 pounds.

The internet gives a lot of interesting answers when about bald eagles and prey weight. I think the Carolina Raptor Center gives the best answer: they can lift half of their weight and carry 1/3 of their weight. Based on these estimates:

• Mom can lift about 5.75 pounds and carry about 3.8 pounds
• Dad can lift about 4.25 pounds and carry about 2.8 pounds

These estimates are in line with the prey we have seen brought into the nest, which has included:

• Fish. The Decorah bald eagles seem to prefer fish to everything else, which means that the majority of their prey is probably around 1 -2 pounds. No muskies, but a lot of trout and sometimes suckers.
• Muskrats. Wikipedia tells me that adults weigh from 1.5 to 4 pounds
• Wild rabbits. Weight reports really vary, but estimates tend to start around 3-4 pounds for adults. The young are considerably lighter. 
• Gray squirrels. Again, estimates vary but in general adults weigh .8 to a little over 1 pound.
• Various birds. Again, I don't know how much they weigh exactly, but the average would be under a pound.

Having said that, I don't think I will ever forget this capture, taken in 2009. One of the adults (probably Mom) brought in the head of a dead fawn (young deer). A newly born fawn might be just inside the range of an eagle's carrying capacity (3 to 5 pounds), but we think the deer was most likely road kill, especially given how deteriorated its body appears to be.

Click here for a look at the area around the eagles nest.

Resources that helped me write this:

• Personal communication from Kay Neumann of SOAR: http://www.soarraptors.org/ Thanks, Kay! (size and weight of bald eagles)
• The Carolina Raptor Center:  http://www.carolinaraptorcenter.org/ (carrying capacity of bald eagles)
• The Raptor Center at the University of Minnesota:  http://www.raptor.cvm.umn.edu/ (size and weight of bald eagles)
• Cleave Books: http://www.cleavebooks.co.uk/scol/calcone.htm (estimating cone size)
• Center for Conservation Biology at the College of William and Mary: http://eaglenest.blogs.wm.edu (egg size and weight)
• Various wikipedia pages for bald eagle info, estimates on the weight of prey animals and wood, including: http://en.wikipedia.org/wiki/Bald_Eagle
• Auburn University: https://fp.auburn.edu/sfws/sfnmc/class/cotton.html (cottonwood)
• Fibonacci numbers: http://science.howstuffworks.com/environmental/life/evolution/fibonacci-nature1.htm

What is infrared light, and why can't eagles see it?

We are starting to get a lot of questions about the night-time illumination of the nest, so I thought I would write a little bit about visible light, invisible light, and our IR illuminators. What we see - the world of visible light - is just a tiny fraction of all the types of light that exist. Infrared light, gamma rays, X-rays, ultraviolet light, microwaves and radio waves are all types of invisible light. Like visible light, they are different because the length of their waves is different.

The illustration below shows the electromagnetic spectrum in its entirety.  The IR portion hangs just off the red end of the visible spectrum.  It spans the frequency range from 780 nm to 300,000 nm (.78 to 300 um) and has a longer wavelength and lower frequency than visible light (click the image to embiggen it):

Illustration courtesy Wikipedia: 
http://en.wikipedia.org/wiki/File:EM_spectrum.svg

Birds have very different eyes than we do. They have four color cones instead of three, more cones and rods to see color and light with, a higher proportion of cones to rods (at least in diurnal birds), and different peak sensitivities to light. As the graph below illustrates, we have narrower spectral sensitivity than birds and are much less sensitive to certain wavelengths of light. However, like humans, birds do not see above about 700 nanometers. While some birds range into UV, IR light is as invisible to them as it is to us.

Illustration courtesy of "Color Vision in Birds": http://www.webexhibits.org/causesofcolor/17B.html

So how can we use an IR illuminator to see the birds if we can't see IR light?
Researching and writing about this stuff makes me want to read a trashy romance novel, but I'll put that aside for now and forge ahead. Here is how it works. The IR spectrum starts at about 780 nm. The LED IR illuminators used on our camera emit 'invisible' light at a wavelength of 850 nm:  well above the 700 nm visibility limit we share with birds, but well below the high-energy 'hot' end of the spectrum.  LED illuminators are also smaller and have lower requirements and range than bulb-type illuminators.

The camera and illuminators are located roughly five feet from the eagles. The illuminators shine IR light on the nest. The IR sensor detects the light and focuses it onto a CCD (Charge Coupled Device) imager chip, which has a spectral response of up to roughly  1,000nm. The chip maps IR wavelengths of light down into the visible spectrum via tiny electric charges generated by IR light falling on to an array of tiny sensor cells. Since the photo-sensitive cells don't distinguish between colors, the camera generates a monochrome image. I suspect it is really a LAB color space, but that is far outside the scope of this discussion. If you feel really nerdy, follow this link to learn more about LAB color spaces. There is a lot more to color than RGB, even for us trichromates! http://en.wikipedia.org/wiki/Lab_color_space.

Can the eagles hear or see the PTZ camera?
The cameras use servo motors to drive the camera along a 360 degree path, which minimizes the amount of time and work it takes to arrive at any given destination. These motors are very quiet - the camera was designed for surveillance - and encased in hard plastic. I suspect that the eagles can't hear the servos; certainly, we don't hear the servos and the microphone is much closer to the camera than to the eagles. If the eagles can hear the servos, the sound is not any more alarming to them than the other noises that make up their sonic landscape - traffic on the nearby road, people at the fish hatchery, wind, tree branches, the brook, the horses, and so on.

Although the young eaglets went through a period last year of seeming quite fascinated by the camera - we wondered if they were interested in their reflections - the eagles ignore it generally. Since it rotates around a 360 degree axis, there does not appear to be much movement (think of a spinning top) and the camera is behind a dome, which helps conceal it. If the eagles can detect movement, it isn't bothering them. Again, a lot of things around them move. Since the camera isn't trying to eat or threaten them, it doesn't really concern them.

In short...
Mammals and birds can't see IR light - to the eagles, the nest is dark at night - but our camera can. We use low power IR illumination devices that are roughly five feet from the eagles. They are not hot and do not emit dangerous radiation or noises. A chip inside the camera does the work of converting the IR image into visible light via tiny electric charges. However, because the chip does not detect color, the image is monochrome.

Experimenting with IR light
To see IR light for yourself, take a television remote, which works via IR. Press a button and look at the LED on the end. You won't be able to see anything. Now, take a digital camera or phone camera (I used an Android HTC), point it at the remote to take a photo, and press a button on the TV remote. You should now, through a digital device with a higher spectral sensitivity than either we or the eagles have, be able to see the infrared light. Like our camera, your camera uses a CCD chip that maps IR down into visible light for humans. But neither we nor the eagles can see IR without technological assistance. Again, the nest is dark at night.

What about the cameras?
A lot of people are interested in knowing more about our cameras. Read this blog post for more information: http://raptorresource.blogspot.com/2013/01/what-cameras-do-you-use.html

The following sources helped me understand all this:

• Personal communication with Travis from 2mcctv, aka our camera salesman. Thanks, Travis!
• http://www.dptips-central.com/infrared-light.html (cameras and infrared)
• http://miguelpedroso.com/Articles/article_nightvision.pdf (light and IR illuminators)
• http://www.onceinnovations.com/downloads/spl.pdf (The Science of Poultry Lighting)
• http://en.wikipedia.org/wiki/Bird_vision#Light_perception (bird vision)
• http://www.jaycar.com.au/images_uploaded/ccdcams.pdf
• (CCD camera explanation)
• Color Vision in Birds": http://www.webexhibits.org/causesofcolor/17B.html
  color vision, birds, and much more
• My husband Ken, who came up with the real-world experiment.

While we wait to see whether M/D Decorah will lay a third egg, I thought I would blog a bit about one of our other nests. The owls at Valmont, Dan and Snowflake, nest in a nest box 260 feet up a smokestack at Xcel Energy's Valmont generating station in Colorado. Owls have big wide heads that swivel almost 360 degrees, huge forward-pointing eyes that excel at gathering light, compact beaks, plump bodies, facial disks, and wing feathers with loose barbs that allow them to fly very silently. Owls swivel their heads because they can't (unlike us) move their eyes.

The tufts of feathers on top of Dan's head are neither ears nor horns. Dan's ears are located under his feathers, at the side of his head, and the right ear is usually set a little higher than the left. Sounds from below reach Dan's left ear first, while sounds from above (including echoes) reach his right ear first. The difference gives him aural 'depth perception', which allows Dan to map sounds three-dimensionally.

Humans don't do this very well. If I'm at a concert, I know the direction the music is coming from, but not the height of the stage the band is playing on. Is it three feet high or five feet high? I need my eyes to tell me. Dan, however, can pinpoint the exact location of the band, or his prey, just by listening. Owls swoop down on their prey from above. Dan's ability to hear and map objects in three-dimensional space helps him catch his quarry in low light, heavy brush, and under snow cover - places where eyes aren't much help. Academically speaking, owls accurately localize both the azimuth (horizontal plane) and elevation (vertical plane) of the sound source. If you like to read about geometry, sound engineering, owl hearing, or awesome stereo setups, google that last phrase.

In addition to offset ears, Dan and Snowflake have facial disks. This concave collection of feathers acts somewhat like a parabolic microphone to direct sound to their ears. In the post on feathers, I mentioned that some birds use them to aid hearing. Owls and Harpy eagles both have facial disks and both hunt under limited visibility. Like other many animals that live in limited or low visibility conditions (catfish and star-nosed moles, to name two) they have developed ways to compensate.

So what is Snowflake and Dan's domestic life like? She incubates the eggs and he brings the food - primarily mice, voles, rabbit, rat, and bird. Although he catches it with his talons, he always carries it in his beak. We've seen Snowflake 'incubate' prey in cold weather, presumably to keep it from freezing, but they don't larder up like the eagles do. They lay two to three round white eggs and begin incubating them immediately after laying - in theory. Snowflake does seem to spend more time off the eggs before all of them are laid. When the babies first hatch, Snowflake and Dan spend a lot of time caring for them. However, as the babies become bouncy, rambunctious 'teenagers', both parents will spend more time out on the perch. The teenage owls act a lot like Sarah, Percy, and Bill in the book 'Owl Babies' - "...and they flapped and they danced and they bounced up and down..."

Like the eagles, owls mate for life - but, like the eagles, mates that die will be replaced. Owls are very territorial and will defend their territory against intruders. Several years ago, the nest box at Valmont was invaded by a strange owl. The two females fought quite viciously before one of them - we think the intruder - was vanquished. Dan and Snowflake have also driven off ravens, which can interrupt nesting, and incubated eggs through thick snowfall and icy rain. Like Bald eagles, they are well adapted to cold weather: they even have feather feet to help protect against cold weather and possibly to sense prey.

2011: The Owls Face A Crow

Dan and Snowflake laid the first egg on 02/13/2012. I estimate first hatch on March 10, although it could be a little earlier or a little later. Xcel Energy has still photos of the pair now and should have the streaming cam back up shortly. You can watch them at our website: http://www.farmyou.com/falcon_cams/index.html (click 'Xcel Valmont Owl Cam') or at Xcel Energy: http://birdcam.xcelenergy.com/owl.html

Information from this post was taken from Collin Tudge's 'The Bird' and the following websites:

• Sound localization: http://en.wikipedia.org/wiki/Sound_localization
• Great Horned Owls: http://en.wikipedia.org/wiki/Great_Horned_Owl
• Ears Map Sounds: http://www.asknature.org/strategy/23622b910ce5191565340ef0b67fa2f1#changeTab
• The Raptor Resource Valmont Owl Thread: http://raptorresource.org/forum/index.php/topic,581.1125.html
• Owl Talons: http://www.owlpages.com/articles.php?section=Owl+Physiology&title=Talons
• Owl Babies, the (fiction) Book. I own it, but also this website: http://denisehughesart.blogspot.com/2011/11/owl-babies-my-favourite-illustration.html

Eagles, Weather, and Feathers!

It was hard not to feel sympathy and concern for Mom last night as she lay in the nest after egg #2, rapidly disappearing under a blanket of snow. Fortunately, she had roughly 7,000 feathers to protect her from the weather.

Different sources provide different answers about how many things birds do with their feathers, but all of them agree that insulation is important. The snow piling up on Mom's back last night provided a clear picture of the insulative properties of feathers: Mom wasn't losing enough heat to melt the snow away from her back. I wish my roof was so efficient.

Feather Anatomy

Image courtesy Ask a Biologist: http://askabiologist.asu.edu/explore/feather-biology

There are two basic types of feather: vane feathers, which cover the birds exterior, and down feathers - looser, fluffier feathers underneath the vane feather. All true feathers are branched: they have a central rachis with rows of barbs on either side. However, down remains light and fluffy, which traps air and helps insulate the bird, while flight feathers hook together like a zipper, to form a continuous 'vane'. Personally, I think of it as dressing in layers: the vane feathers form a sort of 'overcoat' underlain by the soft, insulative down feathers. Given that snow also has insulative properties, Mom was quite warm and cozy under her blanket.

So how else do birds use their feathers? According to 'Ask A Biologist', they help birds fly, keep warm, control body temperature, provide weather protection, aid in swimming, diving and floating (waterbirds and piscivorous birds), snowshoe (Ruffed grouse), toboggan (penguins), brace, feel, hearing (owls, harpy eagles), making sounds, muffling sounds (owls), foraging, keeping clean, aiding digestion, constructing nests, transporting water, escaping from predators, sending visual signals, and camouflage. I think I'm jealous!

Since feathers do so many things, it is unsurprising that they come in more than one type.

Types of Feathers

Image courtesy Ask a Biologist: http://askabiologist.asu.edu/explore/feather-biology

The feathers we find dropped in the woods most often are tail and flight feathers. They seem the same but are actually a little bit different. Tail feathers are balanced evenly left and right of the rachis, while flight feathers have a wider and narrower side. This helps them cut through the air with very little drag. Of course, wing shape also influences flight, but that is for another post. The downy feathers that are good for warmth are shown on the far right. Semiplume feathers are also insulative and help water birds float (although some diving birds are more concerned with going deep - their feathers become waterlogged to help them sink). We think the bristle feathers, found around eyes, nostrils, and sometimes the mouth, help protect those sensitive areas. Filoplume feathers are can be found around the tail and flight feathers. They are thought to be used to sense when the flight feathers need to be maintained.

Although feathers seem light, all of them put together weigh roughly two or three times more than a bird's skeleton does. They also require a lot of maintenance. Most birds have a preen gland near their tails. This gland secretes oil which they spread over their feathers with their beaks. Preening helps remove dust, dirt and parasites from feathers and also aligns them properly. Even with care, feathers eventually begin to suffer damage and must be replaced through molting - an itchy-looking process that renders some birds (but not eagles) flightless. However, the benefits of feathers - flight, protection, insulation, display - far outweigh their costs. We sleep warm in our beds with the benefit of furnaces and blankets. All Mom and Dad need are their feathers.

For more information on feathers, I suggest this website: http://askabiologist.asu.edu/explore/feather-biology. I also took some information from Colin Tudge's book The Bird.

Egg Questions and Answers

We have the first Decorah Eagle egg of 2012! Mom laid it last night at 7:47 CST. Here is a video of the event (by razzle):

Egg Questions and Answers

How long does it take a bald eagle egg to hatch?
There are two ways to think about this: from egg laying to hatch, and from pip to hatch.

• From egg-laying to hatch: Most experts say 35 days, give or take a few. It took the Decorah Eagles 37 days in 2009 and 2011, and 36 days in 2010. 35 to 37 days is a safe bet. 
• From pip to hatch: Pipping occurs when the baby eagle's egg tooth first breaks through the eggshell. It can take as long as a day for the chick to fully hatch. 

How many eggs will the eagles lay? Will all of their eggs hatch?
Although the most common clutch size for eagles is two eggs, the Decorah Eagles have a history of laying three eggs. The breakdown among bald eagles in general is as follows:

• 79% of clutches have two eggs
• 17% of clutches have one egg
• 4% of clutches have three eggs

The eagles hatched all of their eggs in 2009, 2010, and 2011; however, fertilized eggs can fail to develop due to extreme cold, soft shells, or microorganisms. We are hopeful they will have another great year, but we won't know until it happens.

When does incubation begin?
In northern climates, Bald eagles lay eggs when it is still quite cold. They begin incubating immediately after the first egg to prevent the egg from freezing. The eggs hatch the same order and roughly the same interval in which they were laid. While the eaglets are still young, it is possible to identify hatchling number one by its size: it is older and therefore bigger than its nest mates. As the eaglets grow, this difference disappears.

Does Dad help incubate the eggs?
Based on our observations of the Decorah eagles, yes! Before all of the eggs are laid, Mom spends most of the time incubating and laying eggs. Once she is done, Dad incubates about 50% of the time.
Having said that, other nests have reported different divisions of labor, with Mom spending much more time incubating than Dad. We don't know why the eagles act differently from nest to nest, but they do.

Oh no! The eagles aren't sitting on their eggs!
Caring for eggs is a serious business. Everyone knows that eggs shouldn't get too cold, but they also can't get too hot, or the embryos will die. The adults sit on the eggs when they need heat and get off them when they need to be cooled. In particular, the Decorah Bald eagles lay eggs and care for nestlings in late winter and early spring, so their challenges include snow storms, ice, and rain. These things can be frightening to us, but Bald eagles have been coping with them for tens of thousands of years. It is okay for the adults to spend some time off their eggs.

The adult eagle also turn their eggs regularly. Turning the eggs helps keep them all at the same temperature and prevents the babies from sticking to the insides of the eggshells.

What do Bald eagle eggs look like, and how large are they?
Bald eagles lay white, oval shaped eggs. The eggs weigh approximately 125 grams or 4.4 ounces, and are on average about 2.9 inches long and 2.2 inches wide. Size-wise, they are just a tad smaller than a tennis ball, although tennis balls are round, not oval.

What causes the egg to hatch?
Mom and Dad Bald eagle apply heat through incubation, which causes the embryo to grow. At a certain point, it penetrates the air cell - that white sack-like membrane that can also be seen in chicken eggs - and its egg tooth penetrates the shell, creating a hole or pip. It usually hatches 24 to 48 hours after first pip.
The yolk of the egg is absorbed into the baby's stomach at this point, which gives it the energy it needs to hatch.

What is a brood patch?
A brood patch is a bare spot where feathers are missing. Hormonal changes linked to reproduction cause feathers to fall out, which creates a bare patch of skin that allows the incubating bird to better transfer heat to the eggs. Bob estimates that a Bald eagle's skin temperature is about 101F.

Some Bald eagles develop brood patches and some don't. We have not seen a developed brood patch on any of the three adult eagles we have monitored in Decorah, and they all incubated their eggs successfully.

Do Mom and Dad mate for life?
Yes, but if one eagle dies, another eagle will replace it.

Decorah Eagle Egg Videos

• How to tell the difference between Mom and Dad: http://youtu.be/5lARYcL5A50
• The first egg of 2012 being laid: http://youtu.be/j3NjcdT-4U4
• Dad and his new egg: http://youtu.be/G4MYx2J9n8w
• The 'Decorah Shimmy' from 2011 - the eagles settling on their eggs: http://youtu.be/8U_pme0dPhs
• 2011's first hatch: http://youtu.be/8U_pme0dPhs

We also have a third egg at Valmont! Snowflake laid her third egg early this morning or late last night. When we had chickens, I used to think of this time of year as the 'spring egg flood'. It looks like the egg flood has started! Here is a pic from the Valmont nest:


Happy birdwatching, everyone!

We are coming into our busy season! The Fort St. Vrain Bald Eagles laid their first egg yesterday - the same day they laid egg #1 last year. If the Decorah eagles do the same, we won't see an egg there until February 23rd. Note the size difference between Dad (top left) and Mom (lower right). Mom is clearly much bigger than Dad.


The Valmont Great Horned Owls laid their first egg on 2/13/12: 8 days earlier this year. Snowflake and Dan are already on egg #2. Here, Dan brings Snowflake a nice mouse.


So when can we anticipate hatch? Based on last year's dates....

• Valmont Hatch estimated: 3/10/12
• FSV Hatch estimated: 3/28/12

An owl was heard at the Decorah Eagle Nest last night. Video by Razzle:

Watchers probably remember some owl scares last year as well. This is scary for us, but life as usual for the eagles.

Thanks for the photo caps and dates - they are very helpful in tracking important dates!

There were a lot of comments about eagle growth rate on Facebook this morning. According to Gary R Bortolotti, bald eagles may gain more weight per day than any other bird in North America. As in other animals, different body parts may reach adult size at different times. The growth of the legs will be complete about half-way through the nesting period, but the beak and flight feathers won't reach adult size until after the eaglets have fledged, or left the nest. In fact, an eagle's juvenile flight feathers are longer than its adult flight feathers, which it won't get until it is 3 - 4 years old.


The two eaglet pictures are the first and last photographs taken, over a period of slightly less than a month. That should give you some idea of the physical changes the eaglets go through as they grow, although the photo album makes it even clearer. Our little Decorah babies will be taking to the wing before we know it.I've got a Facebook album of Forth St. Vrain eaglet growth 2010, published here: FSV Album

The kestrels have laid a third egg. The photograph of the female kestrel clearly shows what I've heard called her "eye spots". Although no one knows for sure why she has them, the most commonly accepted theory is that they help frighten attackers away. Unlike falcons and eagles, she should lay a bunch of eggs, although not all of them will hatch. Again, unlike falcons and eagles but like many other birds, kestrels are sexually dimorphic in plumage - males and females have different plumage. Wikipedia reports that plumage has more variation between the sexes than size.  Click on the picture for a larger view.

The Decorah eagle babies seem to have gotten off to a nice start today - thank goodness the bad weather is gone!



Mother eagle sheltering her young

Despite today's snow, ice, and rain, the eagle family is doing fine. The parents were very careful to keep their babies sheltered. You can see Mom holding her wings out and up to keep the rain and snow from her young. The bowl of softer materials that the eagles built in the larger nest also helps keep the babies away from the wet. I hope this is the last snowstorm the eagle family faces.

We are also looking forward to peregrine season. I've got some estimated hatch dates:

• Dairyland Genoa: 5/10
• Xcel Sherco: 5/11
• Great River Energy: 5/11
• Xcel Blackdog: 5/16 
• Xcel King Plant: 5/19

The Xcel Pawnee kestrels have laid egg #2. I don't feel quite as comfortable forecasting hatch for them, but I'll guess (a little weaker than an estimate) that hatch will occur around 5/20/2011. The kestrels are very fun to watch - they normally have a large brood which grows very quickly and behaves much more frenetically than the eagle young. Here is a link to a kestrel laying eggs (this is not one of our sites, but the video is very nice):

http://youtu.be/EGmzbS7IOVE

The Valmont owlets are growing rapidly. I need to thank the faithful forum members who have kept me up to date since we are having forum problems. I love these pics and would not get them otherwise. Click the Valmont Owl link in our nestviewer to watch this nest:

http://www.farmyou.com/falcon_cams/

The address looks a little odd because I moved the cams page to another domain (thanks, Ken!) to try to offload some traffic. But it is still the Raptor Resource Project. You can also visit our facebook to talk with other eaglecam fans:
http://www.facebook.com/pages/Raptor-Resource-Project/103786266324668

Eagles incubate for roughly 34-37 days, according to a number of online sources. Last year, the Decorah eagles laid three eggs: one on February 25, one on February 28, and one on March 5. The first eaglet hatched on April 3. This year, the eagles started laying eggs a little earlier, but had the exact same spread: February 23, February 26, and March 2nd.

Eggs in snow.
The eagles are able to incubate
successfully even in this!

As cam watchers have observed over the years, eagles incubate during some very difficult weather. The eggs are laid in a cup of grasses and other soft material (including corn stalks) that raise them above the "platform" of the larger nest. This insulative cup helps retain the heat of the adult eagles and provides additional protection from rain and snow. It also helps keep eggs from breaking (sticks and branches provide a hard, irregular surface) and is nicer for the adult eagles to incubate eggs in - at the risk of being anthropomorphic, I would prefer a bed of soft grasses to one of hard sticks any day.  I suspect the eagles feel the same way.

Some websites state that both male and female eagles are involved in building the nest, while others state that it is usually the female who places branches in the nest. In our experience, both the male and female eagle are involved in building the nest. Bob has observed that nest building is part of the eagles' courtship ritual: bonding begins with courtship and continues through nest building, copulation, incubation, and raising young. Both eagles bring sticks and nesting material in, both place sticks and material, and both move the other eagle's sticks around.

Eagles may also have a brood patch. Feathers are wonderfully insulative and great at shedding water, but can interfere with a bird's ability to transfer body heat to the developing eggs. The brood patch is a bare patch of skin that is well-supplied with blood vessels, making it easier for birds to transfer heat to their eggs during incubation. I don't have a photograph of a brood patch, but there is a real nice one on the Norfolk Eagle site: http://eaglenest.blogs.wm.edu/2011/03/05/incubation-brood-patch/

So who incubates more: the male or the female eagle? The female eagle incubates more, but the male shares incubation duties as well. This is not the case in all birds or even all raptors: the female owl at Valmont, for example, does all of the incubation duty.  In addition to sitting on the eggs, both birds also roll the eggs. This helps assure that all parts of the egg receive heat and prevents the developing embryo from sticking to the egg shell. The parents are very careful not to puncture the eggs with their talons and sometimes "ball" their feet to keep  from damaging them.

As the embryo grows in the egg, it develops (among other things) a sharp point on its beak, called an egg tooth, and a muscle called the hatching muscle. The hatching muscle tips the developing bird's head back. Once it is large enough, the egg tooth will come into contact with the inside surface of the egg. As the chick rotates its sharp egg tooth pierces the egg, causing first a "pip" (hole or crack in the egg) and eventually breaking all the way through.  It is not usually a quick process, and you can hear the babies as they hatch out. 

Pip in egg at left

The eaglets are altricial. According to wikipedia: "In bird and mammal biology, altricial species are those whose newly-hatched or -born young are relatively immobile, lack hair or down, and must be cared for by adults; closed eyes are common, though not ubiquitous. Altricial young are born helpless and require care for a comparatively long time."

The eaglets are not able to thermoregulate, or control their body temperature, until they are 10-14 days old. During this time period, the eagles (usually but not always the mother) stick very tight to the babies. On a warm day you may see the baby eaglets exploring the nest, but on a cold or rainy day, they will be sheltered under a parent or two.

The eaglets will go through a number of physical changes as they grow. On hatching, they will be covered with a light-colored down that is uniform in color. The baby down will be replaced by a darker, medium-grey second down when the babies are between 9 and 11 days of age. Juvenile feathers will start to appear when the young eagles are around 24 days of age. These feathers will be dark, since eagles don't develop adult plumage (dark body, white head) until they are around three years old. The color of the eaglets' beaks and talons will also change as they grow.

Birds grow very rapidly and, according to Gary R Bortolotti, bald eagles may gain more weight per day than any other bird in North America. As in other animals, different body parts may reach adult size at different times. The growth of the legs will be complete about half-way through the nesting period, but the beak and flight feathers won't reach adult size until after the eaglets have fledged, or left the nest. In fact, an eagle's juvenile flight feathers are longer than its adult flight feathers, which it won't get until it is 3 - 4 years old.

For more reading on bald eagle growth and development, check this link out: http://elibrary.unm.edu/sora/Wilson/v096n04/p0524-p0542.pdf

On 3/11/11 I made my first of many big river surveys for falcons on cliffs.  My first stop was under Leo's Bluff near Waukon Junction, IA.  I was pleased to quickly locate two adult falcons back at this cliff.  I saw the adult male falcon strafe a young BE sending a stream of feathers raining down.  This is one of the better cliffs on the Mississippi River to watch and hear the courting falcons.  The road down below this cliff has the least amount of road traffic and least amount of trains. 

I then went to the Bunge North America grain elevator in Mc Gregor, IA.  I found two adult falcons on site. The adult male up near the nest box and the adult female perched on a nearby cliff face.  I stopped in the office to make sure they were aware that the falcons have returned.  I was told that they knew the falcon were back because one of the falcons was quite vocal.  I've never heard of this complaint before.  Before I left the site I parked my car directly under the adult female perched on a dead snag on the cliff face.  The falcon was wailing and she is indeed quite loud.  I could still hear her after driving around the corner of the cliff and all the way to the elevator office.  I stopped back in the office and told everyone that this wailing sound that is part of courtship behavior and should end soon. 

I crossed over the bridge to Prairie du Chein and made my way upstream.  No falcons at the small lock and dam #9 cliff.  I did find two adult falcons at the Lynxville, WI cliff on the northern cliff.

I continued my way upstream and crossed back over the river at the Lansing, IA bridge.  No falcons at the Guider's Bluff, formerly known as Dead Cow Bluff.  I contacted the owners of this cliff as some people have also called this Achafalaya Bluff.  Mrs. Guider was home and I asked her if their cliff was also known as Achafalaya Bluff?  She told me that she has never heard this name before and it has been in the family for 70 years.  So, it appears that the power plant cliff just a short ways downstream is indeed also known to be Achafalaya.  I did find one falcon at the power plant cliff that from now on should be called Achafalaya Bluff.  Returned home 186 miles.

I set off again on another river survey on 3/13/11.  Started out at Lansing, IA and made my way upstream.  No falcons seen at Princess Point near Reno, MN. No falcons seen at the Brownsville overlook cliff. No falcons seen at the Shellhorn cliff.

Saw one adult falcon at Great Spirit Bluff near Dresbach, MN.  I found two adult falcons at Queen's Bluff aka The Bandshell.  This was the first Minnesota cliff overlooking the Mississippi River to fledge a young falcon.  The adults at that first nesting season were two falcons that we captive bred and raised in a rock line room to help imprint them to cliffs.  Both of those adults are now long gone and have been replaced but in our hearts we will always know just how falcons came to first nest on this cliff. 

Heading upstream as I approached the little burg of La Moille, MN. I could see the large cliff face of Trempealeau, WI.  Someday we will have falcons on this cliff as it towers directly over the main channel of the river and several times now I have seen falcons here.

Sadly, no falcons again at the Homer, MN cliff.  I stopped and met with the owners of this historic falcon nest site.  Turns out they have been one of the many followers of the popular RRP BE Cam.  We discussed installing a nest box on the cliff face to improve odds of attracting nesting falcons.

I stopped at Bay State Milling in Winona, MN and found one falcon back on site near the nest box.

Crossed the river in Winona and parked for about 45 minutes under Castle Rock, a lovely cliff about a 1/2 mile upstream from the bridge.  I did not see falcons on that visit but Gary Grunwald reported two falcons courting over this cliff a few days before.  Last year we had two falcons at this cliff before they moved off and it was sad to see this cliff that has had nesting falcons on for so many years sit empty.  Hopefully we will have a successful nesting pair this year.

No falcons seen at Indian Head or Fountain City.  I did notice that the perch on the front of the Fountain City nest box is broken and we will need to rappel down to make repairs.  I now use wooden closet rods for perch material as it is much more durable than using treated 2X2 boards.

As I approached the south end of Alma, WI I saw a male falcon fly from the nest box up on the stack to 12 Mile Bluff cliff directly across from the plant.  He flew back and forth across the cliff indicating to me that he was courting a female.  I stopped for a few minutes and located one falcon perched in a tree up cliff top. 

Spent a few minutes at the Alma Marina cliff where falcons once bred in the single pot hole on the cliff face.  There were about a dozen eagles flying all around the face of this cliff.  No falcons.

Met up with Gary Grunwald at his home directly under Maassen's Bluff.  He has not seen falcons as of this writing but will call as soon as he does.  We have had territorial pairs nesting at this cliff for many years.  However, last year there were two falcons on site but just before what would be egg laying time they disappeared.  Can only hope 2011 is productive.

No falcons at Maiden Rock or West Bluff.  Lake Pepin was still locked up in ice.  This should break any day now.  I crossed the river again at Red Wing, MN and stopped by Red Wing Grain.  I could easily see a falcon at the new nest box.  This is a new falcon nest nest box design that I constructed and supplied to Red Wing Grain.  When you open the top up to the nest box the front is blocked off.  No more worrying about the young falcons falling out and no more having to hang out in space holding something out front to keep the young falcon towards the back of the nest box when being pulled for banding.

It was great to be back on the river.  Soon we will need to inspect our ropes and gear for another banding season.  I will make another river survey this next week.

Please let me know if you have any questions.

The Decorah Eagles laid their third egg today! PeggyJean posted this nice closeup.

In his book "Oology and Ralph's Talking Eggs" Carrol Henderson discusses egg shape. According to Henderson, there are four different general shapes: elliptical (including round/spherical), pyriform, oval, and subelliptical. There are short, medium, and long categories within each, so 12 basic shapes are possible. Bald eagles lay oval eggs that are about the size of a tennis ball, as you can see here. This is the most common shape (Henderson refers to it as the default shape) that are probably most easily formed in the egg as the egg passes through the oviduct.

So how are eggs formed and marked? Some more Henderson:
"The fertilized ovum and yolk are released from the bird's ovary and then enter a portion of the oviduct called the magnum. There the egg white, or albumin, is added around the yolk. In the next portion of the oviduct, called the isthmus, soft inner and outer membranes enclose the egg white. Finally the egg, blunt end first, enters the uterus for an extended period of time where the shell is formed. The pigments (porphyrins) that create colors and patterns on eggshells are produced by the breakdown of hemoglobin from ruptured blood cells...Pigment oozes through the lining of the oviduct and onto the forming shell. Depending on how the egg is moving or twisting in the oviduct, this process results in the creation of spots, streaks, and blotches, with most markings usually at the larger blunt end of the egg."

Of course, shape and color can also protect eggs. Pyriform eggs have a tapered shape (image found on internet). This helps the eggs pack neatly into a nest for incubation, since the pointed ends all face the center; lessens the change of the eggs falling from a ledge, since the eggs roll in tight circles, and may help emperor penguins keep their eggs located on their toes. While I think of eggs as being white, color and markings can help make eggs less visible to predators. Some birds even camouflage their eggs with down or vegetation to hide them.  

In Decorah, the male and female eagle will take turns incubating their three eggs until they hatch on roughly April 1st (it could be a little later, since incubation takes roughly 35 days). This will keep the eggs warm and help protect them from predators like raccoons. The parents will roll the eggs - something we've already seen - pick at the nest, doze, and eat. They will be very busy once the young eagles hatch!
Here's a video of the third egg being laid. Thanks to the many Raptor Resource Project forum members who collect and post photographs and videos.