Monday, July 27, 2015

Bob Anderson

I am deeply sorry to confirm that Bob Anderson passed away this morning. Out of respect for Bob and his family, we are asking that everyone respect their privacy. Official announcements will be made here and on Ustream in the days to come. Our deepest condolences to Bob's family.

Although Bob was very proud of his work with the Decorah Eagles, his heart was truly in his peregrine falcon recovery work. This video tells the story of his cliff work and was a special favorite: https://youtu.be/USQs4Bwxa18

The photo shows him on Great Spirit Bluff. It was one of his very favorites - he loved to be on rope - and is how many of us will remember him. Fly on, friend and mentor. We will never forget you.


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Tuesday, July 21, 2015

Decorah: the eagles, N2, and our plans

Camera and N2
As you might know, wind took down N2 in Decorah very early on Saturday, July 18. The limb that held the nest tree was sheared completely off, several trees in the immediate area were toppled, and a few rows of corn in the field near the nest were flattened. The eaglets and mom were quickly accounted for. Dad kept us wondering until Sunday morning, when he was spotted at a favorite perching place on top of the bluff near the hatchery. As sad as the loss of N2 is, it could have been so much worse. There was no loss of eagle or human life, the family wasn't using the nest, and Mom and Dad are in a period of latency. Once again, a traumatic event for us is simply a part of life for them.

So what's going to happen next? At this point, we are waiting to see what the eagles do. We expect that Mom and Dad will start building a new nest in the fall, most likely in October. We don't believe they will abandon their territory, although we don't know exactly where they will rebuild or whether they will go back to N1. We will be watching closely to see what happens. Will the question of alternate nests finally be answered, at least in this case? Will the eagles rebuild in the woods next to trout creek or choose another spot? When exactly will they start and what will it look like? Thanks to Jim Womeldorf's work in 2013, we have a great basis for comparison!

N2 from the back, splintered limb
Having said that, we can't guarantee a live stream from this location in 2016. Installing and cabling a camera is a huge project, especially if directional boring needs to be done. Once the eagles start working on a nest, we don't want to risk shifting them again. If we can find another solution - a ground cam, for example - we will, but it is hard to plan when we don't know what Mom and Dad will do.

Bob has been thinking about another Decorah eagle cam for quite some time. Eagles can nest anywhere, but a camera needs electricity and internet access - two things that are in short supply at many locations! Fortunately, he identified another possible location just this spring. We will be placing cameras there this fall while we wait to see what Mom and Dad do. If we can't put a camera in N3 this year, we will do it next year. If it is possible to put N3 online via a ground cam, as Jim Womeldorf did in 2013, we will. And if neither of the first two options are possible, we will continue to observe and report on Mom and Dad old-school style. 

A lot of people are asking how Mom, Dad, and the eaglets weathered the storm so successfully. Eagles and many other birds sense changes in barometric pressure hours in advance of incoming weather. While they can't forecast long-term changes in weather (a rough winter, for example), they do sense and respond to relatively immediate weather conditions. The eagle family and other area birds probably sensed the incoming storm and hunkered down in a safe, relatively sheltered area to ride it out. They have long talons with excellent gripping strength (400psi per talon!), and can change their aerodynamic characteristics by changing their shape. So the next time you know rough weather is in the forecast, watch the birds (and bees) and see how they react! 

A few links on the subject: 

Damaged corn




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Friday, July 10, 2015

After The Fledge Weekend!

The eagles have fledged, but we haven't stopped having fun! Come to our After The Fledge party in Decorah, Iowa, from July 16 through July 19. Thanks to apex sponsor Ustream and the Decorah Chamber of Commerce for their support!

To register for the weekend, go here: https://goo.gl/MSmQ3T
For our forum thread on the event, go here: http://goo.gl/pUH3I1

Information

Thursday, July 16: Meet and greet at the opera house in Decorah's Hotel Winneshiek (map: https://goo.gl/SfJaFf).
  • 5pm to 8pm: Enjoy drinks and snacks while you meet moderators and other eagle lovers. We'll have some souvenirs for sale and fun surprises for everyone!
Friday, July 17: Kayaking, scavenger hunt, and volunteering with the Humane Society!
  • Kayaking, 1:00-3:30pm. Scott Iverson has planned a wonderful kayaking trip on the Upper Iowa in the Bluffton area about 15 miles north of Decorah. The scenery is spectacular and the paddling is great! For more information, follow this link.
  • 1-4pm: Volunteer at the Humane Society of Northeast Iowa. Details TBA.
  • Scavenger hunt, all day: The Decorah Chamber of Commerce has sponsored a scavenger hunt through downtown Decorah. Explore the area while racking up badges and competing for prizes! 
Saturday, July 18: Biking, talks, scavenger hunt, and dinner
  • Biking, 9:00am. Hit Decorah's lovely paved bicycle trail with Jim Womeldorf and several Ustream chat mods. We begin meeting at 9:00 and hope to leave at 10am. See you on the trail! 
  • Talks, 2PM: Valders Hall, Luther College. Printable map: http://www.luther.edu/campus/assets/campus_map_8.20.10.pdf.
    Google map: https://goo.gl/LKHavm
    Bob Anderson will introduce talks by Neil and Laura Rettig (Philippine Eagles) and Brett Mandernack (Bald Eagle tracking in the midwest). Neil and Laura will also bring their harpy eagle Cal. 
  • Dinner, 5:30pm. Hatchery. We are serving delicious Iowa pork, chicken, and corn. Don't eat meat? We also have a wonderful vegetarian option! 
  • Scavenger hunt, all day: The Decorah Chamber of Commerce has sponsored a scavenger hunt through downtown Decorah. Explore the area while racking up badges and competing for prizes! 
Sunday, July 19: Volunteer at the Humane Society of Northeast Iowa
  • 10am - 1pm, details TBA. 
Friday - Sunday
  • Tours of the fish hatchery (bring quarters to feed the fish!)
  • 6am'ish: Coffee and pastry at the hatchery
We hope to see you there! 


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Monday, May 04, 2015

Can Bald Eagles Get Avian Influenza?

Can bald eagles get avian influenza? That question is increasingly being asked of us at Ustream and on Facebook. The short answer: We don't know. But let's take a quick look at the landscape so far.

What is avian influenza?
To quote the USDA: "Worldwide, there are many strains of avian influenza (AI) virus that can cause varying degrees of clinical illness in birds. AI viruses can infect chickens, turkeys, pheasants, quail, ducks, geese and guinea fowl, as well as a wide variety of other birds. Migratory waterfowl have proved to be a natural reservoir for the less infectious strains of the disease.

 AI viruses can be classified as highly pathogenic (HPAI) or low pathogenic (LPAI) strains based on the severity of the illness they cause. HPAI is an extremely infectious and fatal form of the disease that, once established, can spread rapidly from flock to flock."

There are at least two different HPAI strains circulating right now: EA/AM-H5N2 and EA-H5N8. The USDA tells us that: "The H5N8 virus originated in Asia and spread rapidly along wild bird migratory pathways during 2014, including the Pacific flyway.  In the Pacific flyway, the H5N8 virus has mixed with North American avian influenza viruses, creating new mixed-origin viruses.  This is not unexpected.  These mixed-origin viruses contain the Asian-origin H5 part of the virus, which is highly pathogenic to poultry.  The N parts of these viruses came from North American low pathogenic avian influenza viruses." The same thing appears to have happened in the Mississippi flyway with H5N2. It is generally believed that waterfowl migrating north carried the virus into Minnesota, although it isn't known how it spread to confined poultry. They most likely contracted the virus while wintering in areas shared with infected Pacific flyway birds.

At present, the USDA reports that:

  • 114 avian flu detections have been reported.
  • 21,644,473 animals have been affected. The vast majority have been on commercial poultry farms that raise chickens, turkeys, mixed poultry, and pheasants.
  • The first detection was reported on 12/19/14 and the last detection was reported on 05/01/15.
While most of the detections have been reported in commercial poultry, wild birds can contract H5N2 as well. The vast majority of cases have been reported in waterfowl, including wigeon, canada geese, mallard ducks, wood ducks, northern shovelers, and teal. Unfortunately H5N2 has also been reported in birds of prey, including:
  • Coopers hawks
  • Red-tailed hawks
  • Gyrfalcons
H5N8 has been reported in:
  • Peregrine falcons
  • A bald eagle
  • A great horned owl
  • Gyrfalcons
On April 30th, Minnesota Public Radio reported that a Cooper's hawk in Yellow Medicine County was the first Minnesota wild bird to test positive for the avian influenza virus H5N2. However, a positive test from a dead raptor only means the bird was exposed to the virus, not that the virus killed it or that the bird spread the virus to other birds. In this case, it was killed when it flew into a window and the virus was found after the carcass was sent to The National Veterinary Service Laboratory in Ames, Iowa.

So what can we make of all this? Based on what we know now, the eagles in Decorah and Fort St. Vrain don't appear especially likely to succumb to H5N2 avian influenza.
  • While H5N2 can be spread through consuming infected prey, it has tended to spread in domestic animals after direct contact with fecal droppings or respiratory secretions of infected birds. This is less likely to happen in a highly dispersed bird like the bald eagle. The virus has only been reported in one bald eagle and a small handful of wild raptors.
  • No large die-offs of raptors have been reported in Minnesota, Iowa, or Wisconsin. All three states are conducting surveillance programs to identify to what extent the virus is present in wild birds.  
  • While waterfowl can carry the virus, it seems to primarily affect domestic large-scale operations. Backyard flocks of chickens have not been infected to nearly the same degree. The USDA has identified just 12 cases in backyard flocks, including five in Washington in January and February, plus others in Idaho, Kansas, Minnesota, Montana, Oregon and Wisconsin. Wild and backyard birds could have been exposed over time to low pathogenic versions of bird flu and developed stronger immunity as a result.
It is believed the virus will die as temperatures warm up and ultraviolet light increases.  In the meantime, I suggest the following links for more information, including influenza updates: 
How are states responding?
News Articles

Did you know?
In Minnesota, the DNR is working to identify the virus in wild birds. The agency is collecting waterfowl fecal samples throughout Minnesota; asking turkey hunters from Kandiyohi, Pope, Meeker, Swift and Stearns counties to submit their harvested wild turkeys for testing; and collecting dead birds of various species reported by the public. 

The DNR has collected 29 dead birds of varying species; nine have tested negative for the virus and 20 results are pending. Test results also are pending on the 37 samples from hunter-harvested wild turkeys. The agency has collected 2,749 waterfowl fecal samples – nearing its goal of 3,000 – and more than 2,200 have tested negative; results for the rest are pending. The waterfowl fecal sampling effort is designed to determine with 95 percent confidence whether the virus is present on the landscape in at least one percent of the waterfowl population. They really want to know if you find a dead turkey or raptor. Go to http://www.dnr.state.mn.us/avianinfluenza/index.html for more information.

The Raptor Resource Project has offered to collect samples while banding this year. I'm guessing the answer will hinge on whether or not we start seeing problems in the wild population. We will keep you informed if anything happens.

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Thursday, April 30, 2015

Red-tailed hawk growth and development in the nest

Eaglets aren't the only thing growing right now! The two eyas red-tailed hawks at Eaglecrest are morphing into adults right before our eyes. Like bald eagles, different parts of their bodies grow at different times and different rates, reflecting developmental priorities and impacting behavior. How will hawks EC2 and EC3 (also known as Speckle and Snickers on the Eaglecrest Wildlife facebook page) grow?

  • 0-7 days: the culmen achieves maximum growth. Red-tailed hawks hatch with a culmen (the dorsal ridge of the upper mandible) that is about 30% of the maximum size it is likely to achieve in the nest. During a red-tailed hawk's first week of life, its already large culmen nearly doubles in length, going from an average of 6.9 mm in length to an average of 12.3 mm in length. Since the consumption of food is the root of all else besides, the hawk's food-consuming apparatus is given developmental priority. While the culmen continues to grow after week one, its rate of growth slows dramatically, becoming almost flat by week five. Bald eagles follow a similar pattern, although they have almost twice the growing time in the nest that red-tailed hawks do and their developmental milestones reflect that.  
  • 7-14 days: third toe and tarsus achieve maximum growth. Eating has priority, but movement isn't too far behind. A young hawk needs to move to build muscle and feed once it is past the point where Mom and Dad simply stuff food into its waiting mouth. In the second week of life, a red-tailed hawk's third toe and tarsus are given developmental priority. The third toe is the real stand out here, nearly doubling in length from 16.9 to 27.9 millimeters. With longer toes and thicker, longer tarsi, the hawks are better able to sit up, move around the nest on their feet and knees, and interact with one another. We see a similar pattern with bald eagles, who reach asymptotic mid-toe and tarsus size about half-way through their nestling period - 40 days, in their case. 
  • 14 to 21 days: body weight achieves maximum growth. With food intake well in hand, young hawks gain weight rapidly. While they've been growing all along, weight gain is the biggest actor in week three. The young hawks spend a great deal of time eating and sleeping as their weight increases. 
  • 21 to 24 days: weight gains decline, independence increases. During the fourth week, weight gain declines, the nestling hawks begin feeding independently, and feather growth takes over. The hawks have the strength and physical structures they need to stand upright on their feet, manipulate food, and feed on their own. At about day 24, the length of primary seven overtakes weight as the best indicator of age.  At this point, fledge is just two or three weeks away. 
  • 24 to 35 days: Feathers take front and center. As fledge comes closer, developmental energy is channeled into growing feathers. The primaries enter their maximum growth phase during weeks four and five, the two weeks prior to fledging. The young hawks will also be growing sub-adult feathers elsewhere, including their backs, their tails (which won't become red until molt two, in their second year of life), and their chests. 
  • 36 to 44 days: Time to fly! Feather growth will slow, but the growth of flight-related muscles is happening in leaps and bounds. Wingercizing will take front and center stage as they young hawks practice for the big event by flapping, wing-hopping, hovering, and eventually taking flight! 
Both red-tailed hawks and bald eagles allocate developmental energy into producing weight and structure first (day 0 to day 24), and feathers second (day 24 onward). While feathers often seem light and simple, these two distinct periods of growth point to the incredible amount of energy needed to produce a proper 'coat' of feathers. Enjoy the hawks now, since they will be leaving the nest soon. It takes just 44-46 days to grow a red-tailed hawk from hatchling to fledgling! 


Resources
Did you know?
Red-tailed hawks are excellent falconry birds. While their are many excellent falconry organizations, I'm most familiar with NAFA. Interested in falconry? Follow this link: http://n-a-f-a.com/
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Wednesday, April 08, 2015

A Four Recap

Earlier this week, a follower asked us for a recap of eagle Four’s life. Four was one of three eaglets that hatched in 2014. While early life in the nest was fairly ordinary, gnats and record-breaking rain interfered with fledging. For the first time that we know of, only one of the 2014 Decorah alumni successfully transitioned to life in the wild. One of Four’s siblings was injured and went to SOAR, where he  remains. The other sibling died of electrocution from a high voltage transmission line not far from the hatchery.

Four’s transition from fledge to flight was a bumpy one. During her first month on the wing, Bob rescued her from a location at the side of a highway, a fence, some deep woods, and a corn field. She roosted on the ground, traveled only short distances, and remained in the vicinity of the nest longer than any other eaglet we are aware of. We were starting to ask ourselves if Four would ever go when, on October 19, she abruptly left. Between June 22, 2014 and March 1, 2015, we received 302 valid fixes on Four. She traveled a total of 686 miles, averaging 2.2 miles a day. She achieved her furthest distance from home on January 8, 2015, when she was tracked 159 miles south of her natal nest. Her longest contiguous flight took place on December 1st, when she traveled 34.8 miles between the Maquoketa River and a roost near Lake McBride. She was electrocuted on March 2nd, roughly 130 miles south of N2.

After Four was electrocuted, we documented her death and reported it to the US Fish and Wildlife Service. We also contacted Alliant Power with photos of the pole under which Bob found her. When we were told it was up to code, Bob decided to get a second opinion. Contact number two told us that several things needed to be fixed to make the pole safe for birds. We passed the information back to Alliant Energy and decided to survey the area for more eagles. Two Ustream mods volunteered to conduct the survey for us. They didn’t find any eagles, but they did learn about another electrocution. They provided photos of that pole and several others. Alliant stated that they would fix the fatal poles and others like them. Thank you very much to IzzySam and Faith for taking this on for us.

We plan to take a trip back into the area where Four died to see whether Alliant fixed the poles as promised. The code we used to follow the travels of our eagles will be repurposed to map electrocutions and identify problem spots. While not every pole can be immediately protected, we can make dangerous poles a priority. Four touched a lot of hearts during her brief life. It is our hope that her death will bring about a safer environment for eagles and other birds.

Four's data is retained here: www.raptorresource.org/maps/latest.php.

What can you do?

  • Find out whether your utility has an avian protection plan. If they don't, they should consider adopting one. An APP helps keep animals, equipment, and people safe. http://www.aplic.org/APPs.php
  • Report electrocuted birds and other animals to your power company. Electrocutions are deadly to animals, harmful to equipment, and potentially dangerous to human beings. 
  • Report collisions to your power company. While our eagles have been electrocuted perching on poles, collisions are also deadly. Swan diverters and other deterrents can be installed.
  • If you are a member of an electric cooperative, make your concerns known to the board. I know of at least one electric cooperative in the process of retrofitting all their poles are safe. Electrocutions destroy equipment, require unscheduled repair time, and are expensive. 
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Tuesday, March 24, 2015

Egg Colors and Shapes

The Chicago Peregrine Program inspired me to write a quick blog on the colors and shapes of eggs. Bald eagles have white eggs, peregrine falcons have eggs that range from light cream through brick red, and red-tailed hawks have pale eggs that are lightly splotched with brown. How and why do the birds we watch lay differently-colored eggs?


In general, female birds inherit egg colors and patterns from their female parents, who are ZW heterogametes. Egg-shell is made primarily of calcium carbonate, a white material, so the default color of all eggs could be considered white. As an egg moves down a female bird's oviduct, it squeezes or presses against glands that produce colored pigments from the breakdown of hemoglobin. Some colors (blues and greens) are applied very early on in the shell forming process, while others (brown) are applied quite late. Color may be applied relatively evenly or in drips and drabs depending on the bird and the speed of the egg through the female's oviduct. If the egg is stationary or moving very slowly, it may be solid, blotched, or spotted. If it is in motion, it will be streaked.

Coloring eggs carries a metabolic cost, so why aren't all bird eggs white? It's believed that birds with white or nearly white eggs have nesting strategies that hide their eggs from predators without the use of color. They might nest in cavities like barn owls, cover their eggs in vegetation like geese, or begin incubation immediately, like bald eagles. Since the eggs aren't visible to predators, camouflage colors and/or cryptic markings don't provide a survival advantage. Birds that lay colored eggs tend to nest in places or ways that are more visible to predators. Peregrine falcons, for example, don't usually begin full incubation until after their third egg is laid. The red color and light speckling helps conceal peregrine eggs when Mom and Dad aren't sitting on them and could make the eggs harder for nest invaders like raccoon to find. Ten or 20 seconds might buy enough time for enraged parents to drive nest intruders away.

So why do red-tailed hawks lay lightly speckled eggs while eagles lay white, highly visible eggs? Both birds begin full incubation right away and nest in fairly similar ways. We don't know for sure, although eagles in general are highly visible (giant nests, flashy black and white colors, six-foot wing spans) while hawks tend to be more concerned with concealment. The differences in egg-coloration might reflect some aspect of their lives we don't understand, but either way, egg-coloration is driven by survival. Hawks must need to conceal their eggs where eagles do not.

Predators aren't the only problem birds face. Some birds commonly dump or lay eggs in the nests of other birds. Splotched, spotted, or streaked eggs may help individual birds recognize their own particular markings and reject eggs that don’t match. So why don't Canada geese, which egg-dump, lay patterned or marked eggs? In this case, I suspect that non-parental eggs don't impact the survivability of parental eggs very much. Canada geese are precoccial, so young require less parental investment once the eggs hatch. Canada geese also time hatching quite tightly, so an egg dumped at the wrong time won't survive.

How about egg shape? Peregrine falcons, Bald eagles, and Red-tailed hawks lay differently colored eggs, but the eggs of all three species are elliptical or oval in shape. We used to think that egg shape was influenced by clutch size and the need to stack eggs, calcium availability, and/or 'the roll factor' - ie, heavily tapered eggs roll in a tight circle instead of rolling off ledges. But in 2017, Professor Mary Caswell Stoddard and her team found that the shape of an egg correlates with the hand wing index, a measure of the shape of the wing.  Faster, frequent flyers have longer, narrower, pointier wings, which translates into a high HWI. Birds that are weaker and less frequent fliers have shorter, broader, more rounded wings, which translates into a low HWI.

So why would flying ability influence egg shape? The maximum size or width of a stretched oviduct is constrained by a bird's body size. Faster, frequent flyers have reduced body sizes and abdominal cavities relative to weaker, less frequent fliers. Their muscular, streamlined body plans and narrower oviducts can't accommodate large, round eggs, but their eggs still have to carry enough nutrients to support embryonic development. These birds maximize egg volume by forming elliptical (oval) or asymmetrical (one round, blunt end and one narrow, pointier end) eggs that can pass through their narrow oviducts while still carrying the nutrients their embryos need to develop and grow.

So how do they do it? While I tend to think of eggs as being shaped by their stiff outer shells, an egg's inner membrane determines its shape. Birds that form elliptical or asymmetrical eggs lay down a membrane that is thicker on the big end and thinner on the pointy end. As an egg moves through a bird's oviduct prior to eggshell development, the thinner end is squeezed and elongated to produce an asymmetrical egg.

In general, egg color and shape is influenced by survival. Female birds that produce more young will out-compete female birds that don't. Egg-color and shape may be influenced by overall health (healthier birds tend to lay more vibrant eggs), metabolic cost, the need to hide from predators, the need to identify one's own eggs, and the shape imposed on an egg by the parent bird's body plan. In all cases, our parents have demonstrated egg-ceptional egg-care! We look forward to eggs soon!

Things that helped me learn and write about this topic:
For more on birds of prey and body plan, read this blog: https://raptorresource.blogspot.com/2017/03/falcon-and-bald-eagle-body-plans.html

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Sunday, March 08, 2015

Decorah Eaglet Four Electrocuted

We are sorry to announce that Four, the single remaining bird from the 2014 Decorah alumni to remain in the wild, was electrocuted on Tuesday, March 2nd. This is the fourth eaglet from Decorah that we know of to die from electrocution. Bob and a good friend picked her carcass up on Thursday and Bob and Brett examined her on Saturday and verified the cause of death.

Bob found her lying underneath a utility pole. He took photographs and sent them to a consultant, who told us the pole was unsafe and made suggestions to improve the safety of this pole and other poles in the area. We brought them forward to Alliant Energy/Interstate Power and Light and are waiting for a response from them.

Why do the eaglets keep perching on power poles? Bob theorizes there is a behavior difference between urban and rural eagles. Rural eagles are programmed to perch in trees because that is what they have available. But urban eagles, including our beloved Decorah family, are exposed to power poles and other man-made structures from the beginning. There are vast amounts of power poles serving our needs.  With eagles beginning to nest in close proximity to man - something new for both species - he believes electrocution will be an increasing concern for urban-fledged eagles and utility companies.

What can you do?

  • Find out whether your utility has an avian protection plan. If they don't, they should consider adopting one. An APP helps keep animals, equipment, and people safe. http://www.aplic.org/APPs.php
  • Report electrocuted birds and other animals to your power company. Electrocutions are deadly to animals, harmful to equipment, and potentially dangerous to human beings. 
  • Report collisions to your power company. While our eagles have been electrocuted perching on poles, collisions are also deadly. Swan diverters and other deterrents can be installed.
  • If you are a member of an electric cooperative, make your concerns known to the board. I know of at least one electric cooperative in the process of retrofitting all their poles are safe. Electrocutions destroy equipment, require unscheduled repair time, and are expensive. 

We will continue our work with the electric distribution industry to address this issue and are researching deterrents for the poles near the nest and elsewhere.

Bob with Four


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Monday, February 23, 2015

Eggs, eggs, eggs!

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. In Decorah, hatches have ranged from 35 to 39 days after lay, with the first egg usually taking the longest. I'd look for first hatch to occur about 38 days after lay, so we're looking at March 28.  In Fort St. Vrain, hatches have ranged from 36 to 40 days after lay, with the first egg usually taking the longest, so we're looking at March 25th. But it could be a little earlier or a slightly later than that.
  • 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 big is an eagle's egg?
Bald eagles lay white, oval shaped eggs. Size-wise, they are just a tad smaller than a tennis ball, although tennis balls are round, not oval. They weigh approximately 125 grams or 4.4 ounces, and are on average about 2.9 inches long and 2.2 inches wide.



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 and Fort St. Vrain  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
Both sets of eagles have hatched all of their eggs to date; 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.

What is in those eagle eggs?
At this point, the developing embryo is still quite small. It is surrounded by the amnion, a fluid-filled bag that helps protect it from jarring and sloshing. The yolk and albumin provide nourishment and additional cushioning, the allantois filters out waste products from the kidneys, and the chorion provides ventilation.  Inner and outer shell membranes help safeguard the embryo from bacterial contamination and keep the egg's insides from leaking out through its highly porous surface.  Embryo, fluids, and membranes are all enclosed in a chalky membrane that strengthens the egg, providing an additional layer of protection from punctures and pressure. An outer cuticle on the chalky membrane (what we think of as the shell) gives texture and even more protection to the eggs.

How do eagle parents care for eggs?
Eagle parents ensure optimal temperature and humidity by alternately incubating, getting off, and rearranging their eggs. While turning eggs might be a matter of instinct, it also prevents the embryos from sticking to the insides of their eggshells, and it optimizes membrane growth. They move very carefully around the eggs, often balling or partially closing their long, sharp talons to keep from puncturing the eggs. Concerned about the amount of time the eagles are spending off the eggs?
Read this blog: http://raptorresource.blogspot.com/2014/02/eggs-and-cold-weather.html

The following resources helped me learn and write about this topic:
  • Bald eagle egg size and color:
    http://eaglenest.blogs.wm.edu/2010/02/04/bale-eagle-egg-size-and-color/
  • What's inside that egg?
    http://eaglenest.blogs.wm.edu/2010/02/26/what-is-in-those-eagle-eggs/
  • The importance of egg-turning:
    http://www.wqed.org/birdblog/2013/04/12/turning-the-eggs/
  • Previous blogs at this site.
Did you know?
Some birds bury their eggs in compost heaps to incubate them. Meet the megapodes!
http://www.wqed.org/birdblog/2011/08/18/born-in-a-compost-heap/

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Tuesday, February 17, 2015

Sex determination in birds

Humans, other mammals, and some insects genetically determine sex via X and Y chromosomes. In the XY sex-determination system, females inherit an X chromosome from each parent, while males inherit an X-chromosome from their mothers and a Y-chromosome from their fathers. Since homogametic XX females produce only X chromosomes, heterogametic XY males dictate the sex of their offspring.

Human watchers (including myself) often apply sex-based characteristics to our beloved eagles. Mom and Dad appear to have many of the same housekeeping arrangements and arguments that we do, so it might be surprising to learn that they turn our XY sex-determination system on its head!

Introducing...the ZW sex-determination system!
Birds, some reptiles, some amphibians, and some fish replace our X and Y with the ZW system. Let's look at a few differences:
  • I'm a female homogametic XX and my husband is a male heterogametic XY, but female birds are heterogametic ZW and male birds are homogametic ZZ. Among other things, this means that Mom's ova determines the sex of the little E's (or D's) we coo over in Decorah and elsewhere. 
  • XY and ZW chromosomes come from different areas of the genome. That means that our system for genetically determining sex is not very closely related to a ZW'er's system for determining sex, even though they both work roughly the same way. 
  • ZW sex determination is dose-dependent, at least in birds. Z doesn't create a male in and of itself. Two Z's (ZZ) are required to make enough male-determining product. Females may be female not because of the W, but because they lack two Z's.
Having said that, ZW females still produce eggs and ZZ males still produce sperm. There are some other similarities between us and them:
  • The non-recombining Y and W chromosomes have both degenerated over time. Today, the mammalian X carries over three times more genes than the Y does, whereas the chicken Z carries over ten times more than the W. Like our Y-chromosome, the W doesn't combine well with its opposite. Deletion, degradation, and mutations occur more quickly on the Y and W than on the X and Z. 
  • Y and W resemble X and Z more closely in 'primitive' animals and plants than in those that have evolved more recently, and both Y and W continue to shrink. Will human maleness and bird femaleness disappear? I don't think it's likely, but some people believe that new forms of sex determination might arise from somewhere else in the genome.  
How does the ZW system affect birds?
We know birds aren't human, even though we might call them Mom and Dad, think of them as friends, and invest them with human-like feelings, duties, and housekeeping systems. Still, it seems odd that they have a system of genetically-determined sex that is so different than ours. How does the ZW system affect them? 
  • Z chromosomes contain more genetic information than W chromosomes. Since ZZ male birds have two Z chromosomes, they are more likely to pass on sex-linked traits than ZW female birds. For example, Decorah daughter (ZW) Four got a Z from Dad and a W from Mom, while son (ZZ) Decorah got a Z from each parent. A male bird contributes a Z to sons and daughters, while a female passes a Z to sons only. Since Dad's Z contains a lot more information than Mom's W, Dad contributes more genetic information on that particular chromosome, especially when it comes to daughters. In humans, females conserve more sex-linked traits than males, and pass them on to male and female children. The opposite is true in birds. 
  • What about that flashy male plumage? We know that male birds conserve more sex-linked traits and pass them on to sons and daughters, but male plumage is more complicated than it appears.  Recent work published in the journal Evolution indicates that female birds were once as flashy as males. We think that sexual selection drove male color evolution (females prefer colorful males), and natural selection drove female loss of color (brighter females and young were more likely to be spotted by predators and competitors). 
  • So what role did the ZW system play? A couple of ideas. W has degraded over millions of years and carries much less information than it did previously. If the gene for female color was located on W, it may have been lost somewhere in the past. Alternatively, Z is more highly expressed than W. The resulting imbalance in hormonal secretions between lower ZW females and higher ZZ males drives fundamental sex differences in phenotype, development, and physiology. A ZW chromosome may not provide enough oomph to turn bright plumage on elsewhere in the genome, assuming it exists in female birds.
  • What about birds of prey? Unlike most birds, female raptors or birds of prey are larger than male birds of prey. And unlike most birds, male and female raptors sport the same plumage. With the exception of kestrels, we can't use plumage color to tell males and females apart. What happened to de-link plumage color with sex and why is size, which is still linked to sex, inverse almost uniquely among birds of prey? Is it expressed in the Z or W chromosomes (W chromosomes are 'large in many raptors'), or elsewhere in the genome? Curious minds want to know!  
Why do we have XY and ZW?
No one knows for sure. All snakes and all birds use ZW determination, and all mammals use XY determination (even when it gets weird, as it does with platypus and voles, X is always present). But fish, amphibians, turtles, and lizards might use XY, ZW, or temperature-dependent selection (TDS) depending on the species. The switch from a variety of systems (ZW, TDS, XY) appears to have occurred around the time the ancestor of all reptiles split from the ancestor of all mammals, but it's not yet clear whether there was an intermediate stage between ZW and XY systems, or whether the transitions occurred directly.  

Is the ZW system really that different? I don't think so. While lovely heterogametic ZW Mom determines sex and handsome homogametic ZZ Dad passes more genetic material to his offspring, males still produce sperm, females still produce eggs, and genetically determined sexes are still differentiated by phenotype, development, and physiology. Whatever the reason for XY and ZW, us XY'ers at the Raptor Resource Project wish all birds the best of luck this spring!

A list of resources that helped me learn about this topic:
Did you know?

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Friday, February 06, 2015

Line-Up: Barred Owls, Great Horned Owls, and Bald Eagles

At A Glance
How do our birds compare? While bald eagles are clearly the heavyweights of the group, barred owls and great horned owls are territorial and can be quite aggressive. All three are generalist feeders. Bald eagles build stick nests, while barred owls and great horned owls nest opportunistically.
Barred Owls
Great Horned Owls
Bald Eagles
Length
16.9–19.7 in
43–50 cm
18.1–24.8 in
46–63 cm
28–37.8 in
71–96 cm
Wingspan
39–43.3 in
99–110 cm
39.8–57.1 in
101–145 cm
80.3 in
204 cm
Weight
1.03–2.3 lbs
470–1050 g
2.0–5.5 lbs 
910–2500 g
6.6–13.8 lbs.
3000–6300 g
Diet
Small mammals, birds, amphibians, reptiles, fish, and invertebrates. 
Diet
Small mammals, birds, amphibians, reptiles, fish, and invertebrates.
Fish, birds (especially waterfowl), small to relatively large mammals, reptiles, amphibians, crustaceans, and carrion. 
Nests
Lays eggs January to April (Iowa). Nests in cavities, other birds' nests, squirrels' nests, and nest boxes.
Lays in February (Iowa). Nests in other birds' nests, squirrels' nests, cavities, dead snags, deserted buildings, cliff ledges, and human made platforms.
Lays eggs mid-February to early March (Decorah). Builds large stick nests and nests in them for multiple years. 
Habitat
Mixed forests of large trees, preferably near water.
All over, although they have a preference for spaces that combine open habitat with forest.
Forests of large, mature trees adjacent to bodies of water 

This line-up makes it pretty clear that the area is as desirable to owls as it is to eagles. Like much of the #driftless, the area encompasses forest, blufflands, running water, ponds, and open spaces. Food is abundant and nests and potential perching spaces abound.

We know how eagles and owls interact. But how do great horned owls and barred owls interact? It looks like great horned owls are a bigger problem for barred owls than they are for bald eagles. The good people at Cornell Lab of Ornithology write that ...A barred owl's most dangerous predator is the Great Horned Owl, which eats eggs, young birds, and occasionally adults. A video made by Dragonlainey on the night of February 3rd features the sounds of great horned and barred owls. It opens with great horned owl calling. Instead of the familar pair hooting, this sounds a bit more like a harnk call - another great horned owl call that isn't especially well-understood (this is a guess on my part and I will add more information if I get it). Familiar GHO hooting starts at about 1:05 into the video, and at about 3:15, we hear an unearthly noise that sounds a lot like the alarm call of barred owls as recorded at The Owl Pages.


Could the great horned owls displace the barred owls or vice versa? The jury is out on that question. Cornell writes that barred owls are...Territorial all year round, Barred Owls chase away intruders while hooting loudly. They are even more aggressive during nesting season (particularly the females), sometimes striking intruders with their feet. We've seen the barred owls attack the eagles in the nest before, and barred owls are displacing spotted owls in the northwestern United States, but I couldn't find any evidence of them displacing great horned owls. While Cornell mentions that great horned owls can shift barred owls on their range, I couldn't find any documentation of outright displacement there, either. I did learn that barred owls are real homebodies. In a study of 158 banded barred owls, researchers sound that none of them displaced more than about six miles away. Compare that to D1's 900+ mile odyssey, or even Four's 100-mile journey!

At present, I suspect the owls and eagles will live uneasily together in inter- and intra-order competition. If we can find and reach the barred owl nest, it would be interesting to band the young and study the family's movements now that great horned owls have arrived.

Additional Owl blogs from RRP
Things that helped me learn about this topic
Did you know?
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Tuesday, February 03, 2015

How Do Bald Eagles Stay Warm In Cold Weather?

Mom, Dad, and eaglets in a late storm, 2011
We get a lot of questions about bald eagles and cold weather. I've written a few posts on the subject, but thought I'd combine them here. Unique body features and changes in physiology and behavior help bald eagles maximize energy gain, minimize energy loss, and incubate eggs in cold temperatures.

To maximize gain, eagles forage in groups, gorge food, and increase the assimilation of ingested food energy. To minimize loss, they become sedentary, seek protective microclimates, and reduce night-time body temperature. Put simply, successful eagles use the least amount of energy to get the most amount of food. Here's how they do it.
  • Foraging in groups (or observing and following other birds on their territory) increases the likelihood that eagles will find food with less energy expenditure than if they hunted alone. Bald eagles steal prey from other eagles and birds (kleptoparasitism), an optimal behavior, at least during periods of food scarcity, for animals that forage together. 
  • Gorging food helps eagles load calories quickly and reduces the likelihood of food theft by another animal.
  • Cold weather causes changes in blood flow. Less blood flows to skin and extremities, making more blood available for visceral organs like the stomach.  This helps eagles reduce energy radiation and increase the assimilation of ingested food energy at a time when every calorie is crucial. 
  • It takes energy to fly, procure sticks, and nestorate. Reducing activity reduces energy consumption and slows metabolism.
  • Sheltering in protective microclimates (thick brush, bluff pockets, sheltered branches, coniferous trees) reduces wind exposure. These microclimes also holds heat more efficiently than open spaces, slowing energy radiation and minimizing loss. 
  • Bald eagles reduce their body temperatures at night an average of 1.8 degrees. This slight hypothermic condition reduces the temperature gradient between their body and the environment, letting them burn fewer calories to stay warm. 
Eagles also have physical adaptations that help them stay warm and incubate their eggs. 
  • Feathers are wonderful insulators. The roughly 7,000 feathers an eagle grows help keep it warm and dry. Stiff exterior vane feathers zip together over smaller, fluffier down feathers, providing an overcoat of sorts to shed water and help keep heat from escaping. Underneath, down feathers trap pockets of air next to the eagle's body, where it is quickly warmed and prevented from escaping. 
  • However, some heat needs to escape during incubation. A brood patch is a patch of bare skin on an eagle's breast. Eagles can roll, wiggle, and tuck their eggs up against the brood patch, effectively transferring heat from the eagle's roughly 104-degree body to the eggs. Since the optimal temperature for incubation is 99 degrees, some heat can be lost. The eagles regulate egg temperature by alternately incubating the eggs and leaving them uncovered. 
  • An eagle's large size helps it retain heat. Eagles have a higher inside-to-surface area ratio than a smaller bird like a chickadee. Less surface area means less heat lost to radiation, which is why, within a broadly distributed group of animals, northern animals tend to be larger than their southern cousins. (http://en.wikipedia.org/wiki/Bergmann%27s_rule)
  • An eagle's legs use counter-current heat exchange to control body temperature. Warm arterial blood flowing from an eagle's core into its feet passes cool venous blood flowing the other way. Heat is exchanged, warming the blood flowing into its core and cooling the blood flowing into its feet. The cooler blood is still warm enough to prevent frostbite, but the lower temperature reduces the gradient between its insides and its outsides, preventing excessive heat loss through its feet. 
  • An eagle's leg muscles are tucked up under its feathers, nearer the warm center of its body, and it has very few soft tissues in its long legs and feet, which are wrapped by thick, scaly skin that helps protect them from the cold. If its feet do get cold, it can always tuck them, often one at a time, underneath its feathers. 
It's hard not to be concerned about eagles and other wildlife during extreme cold events. But eagles and other animals that live outdoors are well-prepared to deal with them. You can help by keeping seed and suet feeders stocked, keeping water available, and providing shelter for birds. The Minnesota DNR offers these winter feeding tips. http://goo.gl/KRqbrv. Our pinterest has some cute ideas, with more to come: http://goo.gl/O4eXWx 

More information on Eagles and Cold
References

Ecological Energetics and Foraging Behavior of Overwintering Bald Eagles
Mark V. Stalmaster and James A. Gessaman
Ecological Monographs
Vol. 54, No. 4 (Dec., 1984), pp. 407-428
Published by: Ecological Society of America

Food Consumption and Energy Requirements of Captive Bald Eagles
Mark V. Stalmaster and James A. Gessaman
The Journal of Wildlife Management , Vol. 46, No. 3 (Jul., 1982) , pp. 646-654
Published by: Wiley on behalf of the Wildlife Society


A Great Read

Winter World: The Ingenuity of Animal Survival by Bernd Heinrich

Did you Know?

Temperature Rhythms Keep (Human) Body Clocks in Sync: http://www.sciencedaily.com/releases/2010/10/101014144314.htm

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Thursday, January 22, 2015

Owls in N2

Owl Defense @ roughly 12:00AM
On Monday morning (01/19/15) at about 12:07AM, our cameras caught an altercation between an invading great horned owl and a defending bald eagle parent. While we've seen brief nest invasions before, we've never seen owls that appear determined to take over the nest. We've had a lot of questions and I'll attempt to answer the most commonly asked here.

Don't Owls Nest In Cavities?
Owls may nest on ledges, dense brush, cavities in trees, holes in the ground, and nests built by other birds. Unlike many birds, owls don't usually make their own nests. Cavity-nesting owls can't drill holes in trees, so they utilize holes made by woodpeckers, rot, or broken branches. While burrowing owls can dig, they prefer to take holes excavated by prairie dogs, skunks, armadillos, or tortoises. Owls that prefer stick nests take nests made by other birds instead of building their own.

Our ideas about owls and cavity-nesting are probably influenced by the 20th-century decline of large nest-building raptors like bald eagles and red-tailed hawks. With fewer bald eagle and red-tailed hawk nests to steal, great horned owls might have been more likely to use cavities. But with bald eagle and red-tailed hawk populations on the rise, there are more nests and great horned owls might be back to taking them.

When is it adopting and when is it stealing? According to much of what I've been reading on the subject, great horned owls often adopt red-tail hawk nests. Since red-tailed hawks aren't using their nests in January and February, it doesn't seem much like stealing to me. Unfortunately, bald eagles and great horned owls both lay eggs at roughly the same time. When Mom and Dad are trying to use the nest they built, our feelings change. How dare those owls steal another bird's nest!

Interestingly, a lot of what I read talked about red-tailed hawks using nests for just one year. While RTH don't always build new nests, do those that do build a new nest every year because they are behaviorally programmed to do so (as was suggested in much of the literature), or do nest adopters help drive their behavior? Great horned owls nest earlier than red-tailed hawks, but their seasons overlap just enough to require replacement nest building on the part of the red-tailed hawks.

Why Aren't The Owls At N1?
We remember N1 as a large bowl surrounded by sticks and filled with grass and cornhusks. But Mom and Dad aren't replenishing it any more. As recent camera work has shown us, the surface is cold and bare and the nest, which is compacting under its own weight, has flattened. While we don't know for sure, I suspect the owls find the soft grasses and bowl-like shape of N2 much more inviting than the barren exterior of N1.

Could The Owls Take Over N2?
I can see three possible scenarios for the nest.

In scenario one, the owls begin laying eggs in N2 at night while the eagles are roosting elsewhere. When the eagles come to the nest the following morning, they find it defended by a pair of owls. In scenario two, the owls keep tangling with the eagles and the eagles abandon the nest. I don't know whether they would reclaim N1, try to build a new nest, or attempt to take over an existing nest somewhere else. In scenario three, as the eagles begin to roost more in the N2 tree at night, it's possible their presence would be a deterrent  and/or the eagles would continue to try and drive them away.  All scenarios are speculation and we will just have to wait and watch nature take its course.

How likely is a nest takeover? Great horned owls are about a third the size of bald eagles, but they are formidable opponents. Unfortunately, I couldn't find much data on nest takeovers, and anecdotal evidence wasn't helpful in figuring out who would probably win. I'd bet on whoever lays eggs first, but even nesting birds have been driven away by nest invaders.

Would The Owls and Eagles Be A Threat To One Another's Young?
No one has appeared especially interested in N1 yet, but suppose we ended up with owls in one nest and eagles in another? We've seen owl predation at Eagle Valley and while Mom and Dad have food preferences, they appear to eat almost anything that flies, swims, or walks on four legs. Both species are territorial and aggressively defend their nests, so it's hard to believe they wouldn't attack one another. Having said that, nest attacks are hazardous and there are accounts of competitive species living side by side. A study of three different species of owls in Finland revealed a surprisingly complicated set of interactions, with prey competition playing a larger role in reduced production than direct aggression. A field report written in 1908 reported great horned owls and bald eagles nesting in the same nest. The author wrote:

This nest had been used for years by Bald Eagles, each annual addition of materials increasing the height until it reached fifteen feet up between the main forks of the tree. At the bottom it was eight feet through, where it was jammed in between the forks, and from here it tapered to four feet, ten feet up, and again spread out to six feet on top where the two Eagle eggs rested on soft, dry grass in the rudely-formed depression. Four feet from the bottom of this huge pile of branches and debris was the Owl's home, containing two freshly laid eggs.

 So in short, I don't know. Bald eagles and great horned owls overlap in a lot of places, they don't compete for exactly the same food base, they forage at different times of the day, and the vicinity is well-stocked with prey. We'll be watching intently (and asking for your help with documentation) if they end up nesting in close proximity. We will continue to watch the nest or nests regardless of who ends up nesting in them.

Can You Do Anything About It? 
No. This is a natural event and we believe it would be unethical to interfere. Beyond that, our permits don't allow us to take healthy owls and interference could easily do more harm than good. If an eagle or owl is hurt, we will do our best to find it and get it to a rehabilitation facility.

Will The Owls Take Advantage Of The Hatchery?What do great horned owls eat? Like eagles, almost everything. Cornell University tells us that they eat mostly mammals and birds—especially rabbits, hares, mice, and American Coots, but also many other species including voles, moles, shrews, rats, gophers, chipmunks, squirrels, woodchucks, marmots, prairie dogs, bats, skunks, house cats, porcupines, ducks, loons, mergansers, grebes, rails, owls, hawks, crows, ravens, doves, and starlings. They supplement their diet with reptiles, insects, fish, invertebrates, and sometimes carrion.

Having said that, they have a real preference for mammals. I don't think they would take advantage of the hatchery unless mammals were in very short supply.

What Do You Think About It?
We would like the eagles to stay in the nest and be productive. If that doesn't happen, we would like the nest takeover to occur without injury or loss of life to the eagles or the owls. More than anything, we hope that they don't engage in a prolonged inter-species conflict that results in the maiming or death of young. We won't interfere with life in the nest but as I stated earlier, if an eagle or owl is hurt, we will do our best to find them and get them to a rehabilitation facility. Remember that while both species have serious talons and beaks, conflicts don't have to involve injury.

A video chronology of owls at N2. Please let me know if the comments if I'm missing one.

10/16/14: Noisy GHOs on N2: http://youtu.be/2CTgZ_1BDLM
10/26/14: GHOs in N2: http://youtu.be/BcEgBTnzG7A
11/18/14: GHOs are back: http://youtu.be/26PWTnrJaf4
12/17/14: Early morning visit by the owls: http://youtu.be/J2X_62MHR5o
01/02/15: The owls are back: http://youtu.be/LNvqXXK9jyY
01/04/15: The owl are back (again): http://youtu.be/onuXDxuIbbE
01/05/15: Two owls visit: http://youtu.be/XGVph_UlrmQ
01/07/15: An owl came to check out the nest: http://youtu.be/brFh48BjgxI
01/10/15: Owl on nest: http://youtu.be/v161nRghtOM
01/18/15: Owl strike on nest: http://www.ustream.tv/recorded/57746729/highlight/594763
01/20/15: Owl is back: http://youtu.be/VtL3AFsnAPw
01/22/15: Owl with mouse gift for his mate: http://youtu.be/1d92Du_Hr0o

I have written a couple of posts on owls in the last few years. A few links:
Things that helped me learn and write about this subject: 

Competitive and Predatory Interactions among Raptors: An Observational and Experimental
Study. Author(s): Harri Hakkarainen and Erkki KorpimäkiSource: Ecology, Vol. 77, No. 4 (Jun., 1996), pp. 1134-1142. Published by: Ecological Society of America. Stable URL: http://www.jstor.org/stable/2265582 

Bald Eagle (Haliætus leucocephalus) and Great Horned Owl (Bubo virginianus) Occupying the
Same Nest. Author(s): J. Warren JacobsSource: The Wilson Bulletin, Vol. 20, No. 2 (Jun., 1908), pp. 103-104. Published by: Wilson Ornithological Society. Stable URL: http://www.jstor.org/stable/4154205 

Close Nesting and Aggression Contacts between Great Horned Owls and Red-Tailed Hawks
Author(s): Dwight G. Smith. Source: The Auk, Vol. 87, No. 1 (Jan., 1970), pp. 170-171. Published by: American Ornithologists' Union. Stable URL: http://www.jstor.org/stable/4083679 


Many thanks to Karla Bloem from the International Owl Center for providing information and feedback. You should visit the website (seriously, please do.):
 http://www.internationalowlcenter.org/
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Tuesday, December 02, 2014

#GivingTuesday

We have a day for giving thanks. We have two for getting deals. Now, we have #GivingTuesday, Tuesday, December 2nd, a global day dedicated to giving back! If you like the work we do, please consider making a donation. You can donate online via paypal or mail a check to the Raptor Resource Project, PO Box 16, Decorah, IA 52101.

What does the Raptor Resource Project do? We:

  • Work with government agencies, private businesses, and other non-profits to monitor and band peregrine falcons at over 40 sites. Our region stretches for well over 500 miles and encompasses parts of three major rivers - the Minnesota, the St. Croix, and the Mississippi. 
  • Provide one of the world’s largest public wildlife education programs to countless school kids through our live online streams, interactive chat, facebook page, and blog. Our Decorah eaglecam alone has been watched by over 302 million people worldwide since 2011. We maintain over 20 public and private cameras to monitor and learn about birds of prey.
  • Build and install nest boxes to bolster bird of prey populations in Iowa, Wisconsin, and Minnesota. 
  • Provide information and consultation free of charge to other organizations and businesses who are interested in initiating their own nest box programs.
  • Track and share data about free-living bald eagles in conjunction with Brett Mandernack at Eagle Valley.

These things all take money. As of 2014, our annual expenses were hovering around $87,000 per year:

  • Staff costs a little over $42,500 annually.
  • Equipment – computers, camera upgrades and maintenance, tools, encoders, software, transmitters, and so on – costs around $17,000 annually.
  • Supplies – primarily cable, tools, climbing equipment, banding equipment, bands, installation hardware, maintenance equipment, and lumber – cost around $5,000 annually.
  • Satellite data costs $4,225 dollars annually.
  • Internet access costs $4,500 annually.
  • Other/Miscellaneous costs around $9,000 annually. This category includes gasoline, electricity, travel-related costs, equipment fabrication, and a furnace and propane so we can heat the shed!
  • One-time costs and special projects vary widely. In 2013, for example, we spent $19,000 in Decorah to get video cable over to N2. While that was unusually expensive, it isn't uncommon for costs to crop up given the amount of cams and equipment we have. 

We have some exciting projects coming up in 2015 and 2016, including a wild Philippine eagle cam and an expansion of our eaglecam project! Our income is generated entirely by small donations from viewers of our various cams, and we sincerely appreciate your generosity and support of the Raptor Resource Project mission. Would you please help us make a difference with your donation?

Thank you so much for your support and we hope you enjoy watching in 2015!


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Wednesday, November 19, 2014

Why Are The Eagles Working On The Nest?

2016 note: The winter of 2014 was mixed. To date, the winter of 2016 has been far warmer than normal. Click here for a synopsis of 2014/2015 - the season this blog was written for. 2016 is starting much like 2014, so it will be interesting to see how we finish.

Why are the eagles working on the nest? Are they predicting a hard winter? Does nestoration frequency or intensity signal a snow and cold yet to come? These questions have turned up in a few places recently. It appears that the recent flurry of nest activity does not signal another unusually cold, snowy winter, although it looks like might get one anyway!

So why are the eagles in Decorah and Fort St. Vrain working on their nests? Among non-tropical birds, many activities (reproduction, molt, migration) are linked to daylight length. We've primarily discussed the photosensitive period of bird life here, when daylight lengthens, gonads start swelling, and human watchers start counting the days until eggs are laid. However, birds also have a photorefractory period that in many northern birds begins slightly prior to summer solstice in mid-June. Gonads start shrinking, a new hormonal regime takes precedence, and many northern birds start preparing for winter. This might include social behaviors like flocking (something many mid-westerners start seeing in August), the cessation of care for fledglings, serious eating in preparation for migration, and dispersal from home territories. Researchers are quite sure that gonadal changes drive vernal (spring) behavior, but autumnal behavior is a lot harder to figure out.

Since daylight length is so important, we should probably chart it, right? We'll start with Decorah's photo-period from December 21, 2013 to December 20, 2014. At Decorah's latitude, the cycle of 365 days plots into a nice bell curve that looks something like this.

Daylight length in Decorah 2014. Charts here: http://goo.gl/71yGBx
Of course, there are other ways to plot daylight length. What happens if we consider each month separately? That graph yields a more complex pattern. Some months are rising, some months are falling, and daylight length is approximately equivalent on several days in spring and fall. For example, Decorah enjoyed 10:49 hours of daylight on October 20...very similar to February 20, with 10:44 hours of daylight. We'll get back to that soon.

Daylight plot by month.
Let's break it down even further. Figures one and two plot daylight length. But what does it look like if we plot the rate of change instead?
Do change rates also influence photosensitive and photorefractory periods? 
This graph shows the rate of change compared to overall daylight length across one year. The flat planes show time periods where daylight length is changing at a steady rate: +3 minutes per day at the top of peak one, and -3 minutes per day at the top of peak two. The valleys display transient states where daylight length is changing more rapidly, with the exception of the zero plane that occurs around each solstice.

For many birds in northern latitudes, the photosensitive period occurs primarily in cycle one and the photorefractory period occurs primarily in cycle two (with a little overlap into the tail end of cycle one). So why are they working on their nest during the photorefractory period, especially if weather prognostication isn't involved? A few thoughts.
  • The eagles might be influenced by daylight length. Daylight length is quite similar in mid-February and mid-October. This might encourage bonding activities in the photorefractory period that echo those in the photosensitive period, especially between territorial mates. 
  • The eagles might be impacted by Zugunruhe (migratory restlessness, which is also influenced by daylight length). I know Mom and Dad don't migrate, but many eagles do. Perhaps the suite of behaviors and hormones that direct migration in some birds influences our eagles to return to nest-building. Both adults certainly seem to have nest-building restlessness! 
  • The eagles might be influenced by memory. Yes, light is the most important zeitgeber in Mom and Dad's world. However, study after study has shown that birds learn, remember, and draw on experience. Could last year's brutal winter be influencing this fall's flurry of nest preparation?
Light might be the most important zeitgeber in Mom and Dad's world, but it isn't the only one. In addition to dwindling hours of daylight, a flat-lined change rate, and no real photosensitive period day length matches, our eagles will be coping with cold and snow. As happened last year, we expect to see less of them until their gonads fire back up following winter solstice. Stay safe, Mom and Dad! We look forward to seeing you whenever you visit!


I got curious about daylight length in NE Florida since the eagles there just laid egg number one. How long are their days right now as compared to Decorah? The US Naval Observatory tells me they had ten hours and 33 minutes of daylight today, as compared to nine hours and 36 minutes in Decorah. Interestingly enough, our eagles lay eggs when we have roughly ten hours and 44 minutes of daylight. While eagles are influenced by other zeitgebers such as health, food availability, and age, this underscores the important role that photoperiod plays in the lives of our birds.

It's pretty straightforward to calculate photoperiod for the Decorah eagles, since they don't migrate and live at a latitude with obvious photoperiod changes. But how about connecting photoperiod to physical changes in the Arctic Tern, a bird that annually migrates from Greenland to Antarctica? Or the Kiwi, a nocturnal bird? How about birds that live in places like American Samoa, which has a shortest day only 1 hour and 41 minutes shorter than its longest day? The more I watch birds, the more questions I have about them. 


Things that helped me learn about this topic:

  • Personal communication, Bob Anderson. Thanks for the lesson on photoperiodism! 
  • Astronomical Applications Department of the U.S. Naval Observatory: http://aa.usno.navy.mil/index.php. If you like charting, this site is worth a visit.
  • Paper: Circannual rhythms in birds, Eberhard Gwinner. Current Opinion in Neurobiology 2003, 13:770–778.
  • Paper: Gwinner E, Scheuerlein A: Photoperiodic responsiveness of equatorial and temperate-zone stonechats. Condor 1999, 101:347-359.
  • Paper: Dawson A, King VM, Bentley GE, Ball GF: Photoperiodic control of seasonality in birds. J Biol Rhythms 2001, 16:365-380.
  • Book: Living on the Wind: Across the Hemisphere With Migratory Birds by Scott Weidensaul. This would make a great present for the bird-lover in your life! 
  • Book: Sync: How Order Emerges From Chaos In the Universe, Nature, and Daily Life by Steven Strogatz. Another great book, although it isn't about birds!  
  • Website: The Arctic Tern Migration Project. http://www.arctictern.info/ 
Thanks for reading! 
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