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.

Mae's eggs, 2000, Xcel Energy Allen S. King Plant. Some egg color variation is normal.

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.

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'.

I'll cover the babies in a later blog post.

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)

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.

Egg developmental calendar
Like hatched birds, embryonic birds go through stages of development. The following list is courtesy A. L. Romanoff, Cornell Rural School Leaflet, September, 1939.) (Fig. 9). Website: http://chickscope.beckman.uiuc.edu/resources/egg_to_chick/development.html

FIRST DAY:

16 hours - First sign of resemblance to a chick embryo
18 hours - Appearance of alimentary tract
20 hours - Appearance of vertebral column
21 hours - Beginning of formation of nervous system
22 hours - Beginning of formation of head
23 hours - Appearance of blood islands - vitelline circulation
24 hours - Beginning of formation of eye

SECOND DAY:

23 hours - Beginning of formation of heart
35 hours - Beginning of formation of ear
42 hours - Heart begins to beat

THIRD DAY:

50 hours - Beginning of formation of amnion
60 hours - Beginning of formation of nose
62 hours - Beginning of formation of legs
64 hours - Beginning of formation of wings
70 hours - Beginning of formation of allantois

FOURTH DAY:

Beginning of formation of tongue

FIFTH DAY:

Beginning of formation of reproductive organs and differentiation of sex

SIXTH DAY:
Beginning of formation of beak and eggtooth

EIGHTH DAY:

Beginning of formation of feathers

TENTH DAY:

Beginning of hardening of beak

THIRTEENTH DAY:

Appearance of scales and claws

FOURTEENTH DAY:

Embryo turns its head toward the blunt end of egg

SIXTEENTH DAY:

Scales, claws, and beak becoming firm and horny

SEVENTEENTH DAY:

Beak turns toward air cell

NINETEENTH DAY:

Yolk sac begins to enter body cavity

TWENTIETH DAY:

Yolk sac completely drawn into body cavity; embryo occupies practically all the space within the egg except the air cell

TWENTY-FIRST DAY:

Hatching of chick

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.

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:  http://en.wikipedia.org/wiki/Lab_color_space. There is a lot more to color than RGB, even for us trichromates!

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. 

• Our pan tilt zoom Camera is model  KT&C KPT 10T
• Our color day/IR night Camera is model KT&C KPC N300NH

These cameras are robust, look great, and are cold-tolerant. They can easily be ordered from Travis at 2mcctv by calling 877-926-2288, or you can check out the full product line at http://www.2mcctv.com/

If you need a wireless solar-powered system, we recommend Sun Surveillance:
http://www.sunsurveillance.com/

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.

Video from 02/23/12 at the Decorah Bald Eagle Nest
70Chico1: DECORAH EAGLES FEB. 23, 2012 9:07 AM CST PANNING WITH CLOSE U


DECORAH EAGLES FEB. 23, 2012 12:05 PM CST SWITCH OVER & EGGS LEFT ALONG


Razzle: Decorah Mom Spreads Wings Over Nest and Nods off 2-23-12 6:49pm CST

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