How and Why to Donate to the Raptor Resource Project!

What does the Raptor Resource Project do? We are a 501c3 that specializes in the preservation of falcons, eagles, ospreys, hawks, and owls. In addition to bringing you the Decorah Eagles, Great Spirit Bluff Falcons, and other birds of prey, we create, improve, and directly maintain over 50 nests and nest sites, provide training in nest site creation and management, and develop innovations in nest site management and viewing that bring people closer to the natural world. Our mission is to preserve and strengthen raptor populations, expand participation in raptor preservation, and help foster the next generation of preservationists. We are asking for donations today to support our work. You can donate online at PayPal by following this link, or you can mail a check to:

The Raptor Resource Project
PO Box 16
Decorah, IA 52101

As a nonprofit environmental organization, we depend on donors, research, and our other programs for our entire budget.  In the upcoming year, we plan to:

• Establish a wild Philippine eagle camera. We are waiting for a report from Cornell on how to proceed. At this point, our costs are unknown.
• Continue our collaborative raptor nest-box, trapping, and monitoring programs, including banding at all of our peregrine falcon sites in Minnesota, Wisconsin, and Iowa. If the weather holds, this will be a banner year for us. I believe we could end up banding 70 or more falcons!
• Upgrade at least three more sites to high definition digital cameras. We would like to do more if we can! 
• Continue to provide one of the world’s largest public wildlife education programs to countless classrooms through our unequaled Ustream channels, interactive chats, facebook page, and blog.
• Hire a full-time director. Our current director is volunteering all of his time to lead the Raptor Resource Project. He’s done a wonderful job and we would like him to work for us full-time. He was selected by Bob and has been absolutely critical in carrying Bob's legacy and plans forward. 
• Explore partnerships with schools and other organizations to benefit wildlife and land preservation in the Driftless Area. At present time, we are working with Hoo’s Woods Raptor Education and Rehabilitation Center and several other partners on a kestrel poster project.  Bob had become very interested in kestrels and we are interested in re-launching that project.
• Build and deploy online tools to develop appropriate tools to easily capture and share data from our sites and other sites.

With our volunteer director, our current costs hover around $118,700…but we will need to raise more money to bring our director on full time. In 2015, our expenses looked like this:

• $55,000 for staff and contracts. In 2015, we incurred extra expenses for our N2B build and two camera installs: one at N2B and one at Decorah North Nest. These were intensive projects that required a lot of help. The N2B camera installation alone took nine people five full days of work from dawn past dusk. Five or six volunteers also showed up to help at will.
• Camera installations – a computer and peripherals, cameras and peripherals, labor and materials, high speed internet, caretaker/rental costs, and audio systems - cost $17,500 per site, for a total of $52,500 in 2015.
• Supplies – primarily cable, tools, climbing equipment, banding equipment, bands, installation hardware, maintenance equipment, and lumber – cost around $2200 annually.
• Other/Miscellaneous costs around $9,000 annually. This category includes gasoline, electricity, travel-related costs, equipment fabrication, and propane so we can heat the shed!

Our income is generated entirely by 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 2016! Go eagles and falcons! As we celebrated D24 yesterday, I couldn't help but think of Bob, the person who started it all. A few links:

• D1's capture and Bob's happy dance! https://youtu.be/CDetJJt4V5U
• A celebration of Bob's life: https://youtu.be/QMPbzWYKdMQ

Do bald eagles delay incubation?

2014, Egg #2. Temp with windchill: -40F.

Do bald eagles delay incubation? It wasn't an a question we've thought about much, since bald eagles in Iowa usually lay eggs in temperatures under - sometimes well under - freezing! However, this year was quite a bit warmer, and the eagles in Decorah and Fort St. Vrain seemed to spend more time off the first two eggs than we are used to.

The question seems pretty cut and dried. After all, peregrine falcons delay full incubation very consistently until the third egg in a four-egg clutch, and the fourth egg in a five-egg clutch. In cold years (2013, 2014), we tend to experience higher losses than in warm years, since eggs one and two can freeze and die prior to the beginning of full incubation. However, it isn't that simple with bald eagles and many other birds.

2016, Egg#2: Temp no windchill: between 25-40F.

According to Professor Jim Grier, birds often start incubation slowly or gradually when temperatures aren't in the freezing range. Freshly laid eggs can spend a lot of time in the zone of suspended development (roughly 28.4 to 80.6°F or -2°C to 27°C) with no harm to the egg or embryo. While I don't have storage times for bald eagle eggs, Wikipedia tells me that the freshly laid eggs of domestic fowl, ostrich, and several other species can be stored for about two weeks when maintained under 5 C. That is quite a bit longer than the time between eggs one and two in a bald eagle nest!

Temperature aside, why do some birds begin incubating immediately? In a blog on the subject, David Hancock discussed two theories of immediate incubation: one, to protect eggs from marauding ravens and other predators, and two, to assure the survival of at least some young during periods of food scarcity. In the last case, the 'strategy' assumes that it is better to have one or two surviving children than no surviving children at all.

However, there are more benefits to delaying incubation so eggs hatch closer together: indeed, the survival of many waterfowl depends on it since adults leave the nest 24-48 hours after hatch begins, whether all of the eggs are hatched or not. Perhaps most importantly, delaying incubation helps assure that rapidly growing young are in the same stages of development. In the presence of an abundant food supply, more young will likely survive when incubation is delayed, since there will be less variation in size and ability between older and younger siblings, and food should be shared more equitably as a result.

Professor Grier pointed out that the nature (if not essence!) of biology is variation. This caused me to think back on eagles and monogamy. When we first started this adventure, everyone 'knew' that eagles were monogamous and mated for life. A new mate would be taken only if the old mate died. Remember when that was true? But once we really started looking, eagle relationships turned out to be more complicated. While many eagle couples appear to be monogamous, we've also documented extra-pair copulations, eagle 'divorce', polygyny, and polyandry.

The same is undoubtedly true for incubation. Professor Grier wrote that he would expect variation among different pairs of bald (and other eagles) in how much time they spent off the egg(s) both at the start and as incubation proceeded, as well as under different conditions such as temperature, humidity, and precipitation. We've certainly seen that in Decorah. In 2014, February's mean temperature was 9.4F - the coldest in 20 years of recording! Under those conditions, Mom and Dad incubated almost constantly. But in 2012, February's mean temperature was 27.8F - not the warmest ever recorded, but quite close to it. As indicated by video footage and all of the blogs and posts we did on the subject, Mom and Dad spent much more time off the eggs in 2012 than they did in 2014. While weather is clearly a factor, David Hancock noted timing variability between rural and urban bald eagles, and speculated that the presence of predators might make a difference in whether incubation was delayed.

The world is not a static place. Animal populations fluctuate as food supply, weather, and disease cause cycles of booms and busts. High populations and/or low food supplies can result in massive dispersals or irruptions as birds compete for territory and food. Populations may adopt different behaviors at different levels of density and food abundance, perhaps becoming less aggressive in a situation where neighbors and food are both in high supply. Everything changes over time: given a large enough timescale, the continents themselves flow like water. In that light, it is no surprise that eagle incubatory behavior might vary, or that eagles might adopt different behaviors as their population and/or the world around them changes.

So philosophy aside, can we really answer the question of delayed incubation in bald eagles and other birds? That's a tough one. The onset of incubation doesn't seem to involve timing in most species of birds, since they appear to be responding more to external factors than to an internal clock. This makes it hard to define what exactly 'delay' is for most birds. If I'm staying off my eggs because it is warm out, am I really a delayed incubator? If I almost always incubate right away because I lay eggs in sub-zero temperatures, am I really an immediate incubator?

Short answers are often necessary in our instantaneous and highly-connected world, so here is mine: "Bald eagles may or may not begin incubation immediately after the first egg is laid, depending at least in part on local factors that include temperature, humidity, precipitation, and predators. Apart from that, bald eagles exhibit variability: that is, not all pairs act the same way, even given the same or similar situations. There is more to learn, so keep watching, keep documenting, and trust the eagles!"

I'm going to close by quoting Professor Grier again: "The nature (if not essence!) of biology is variation." In my experience, almost every time we say a species always does this, or never does that, the species proves us wrong! Onset of incubation and mating systems are just two more examples of that.

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Our ideas about birds have been shaped by how we observe them. Professor Grier pointed out that in the past, normal incubation details for various birds were studied from blinds, long-term and time-lapse photography, and with electronically telemetered artificial eggs, nest thermometers, treadles or scales to measure adult presence on the eggs. He wrote: "Eagle cams provide a whole new opportunity to observe and study traits such as incubation behavior (by individual parent, gender, total time, and under various environmental conditions) on increasing sample sizes of birds under undisturbed conditions." In other words, nest cams give us an unparalleled opportunity to observe large populations of birds in the wild, relatively free from human interference. Who knows what we will find, or what theories and beliefs will be challenged? We've got the cameras in the field. The next step is to develop appropriate methodologies and tools to enable large scale data collection across species and populations.

Thanks to the following for helping me learn about this subject.

• Personal communication, Professor James Grier. Any mistakes I made in interpreting his email are my own. 
• Personal communication, Bob Anderson. Bob used to tell us that eagles were pretty smart, but peregrine falcons were only about as smart as garter snakes. Even though he loved falcons, he believed that their lower intelligence made them less variable in their response to external stimuli. While that was outside the scope of this blog, I will return it later on.
• David Hancock's blog on Bald Eagle Laying and Hatching Sequences

Thoughts on the sub-adult nest-intruder

We had an intruder at the Decorah North Nest on March 13th. While Dad was in the nest incubating the pair's single egg, a roughly four-year old female eagle perched on a limb right next to the nest tree. He responded by covering the egg, softly vocalizing, and ruffling his feathers. The whole encounter lasted about fourteen minutes.



I was intrigued by Dad's soft vocalizations. Why didn't he call a little louder? I went to our panel of eagle experts for an answer. Jim Grier and Brett Mandernack both provided insights into Dad's behavior. Note that neither Jim nor Brett referred to the eagles by title (Dad) or sex. Those additions are my own.

Jim has extensively studied eagles in Ontario and along the Mississippi River Valley. He noted that the density of eagles is getting so high that it might be changing eagle "society" and interactions, or bringing out behaviors that don't occur in lower density [and perhaps limited food-base] situations.While we don't think of the Decorah North Nest as urban, bald eagles along the Mississippi river and its environs are urbanizing as the population density grows. Our initial ideas about the lonely majesty of the bald eagle may have come from observing lower-density populations in a landscape much less impacted by human beings.

Jim explained that the soft vocalizations sound more like typical young- or mate- calls made at close range between young and parents or between mates (as in food-begging by young toward adults or females toward males). He also pointed out the direction of Dad North's gaze. Dad North didn't spend much time looking at the eagle on the branch, almost as it he was familiar with her. To quote:

"Direct" gaze can include both truly direct, focused straight at -- with both eyes and holding the gaze -- or what I call indirect-direct, mostly a side-ways look with occasional looking away and often with raised hackles, all of which is the prelude to an attack if an intruder doesn't back off. When an eagle is presented with a new individual that it doesn't know but which it is not particularly concerned about, it will "study" the new individual, looking directly at it and looking at different parts of its body. Then it will look away briefly, then look back and study it some more, and alternate with increasing lengths of time looking away and shorter periods of gazes ... until it becomes "familiar" with the new individual and then, subsequently, usually only glance occasionally at the individual but mostly seeming to ignore the familiar bird nearby. 

As upset as Dad might look to us, his indirect gaze indicates he might not have been especially concerned with the intruder. There was just one brief threat-bout toward the bird on the branch when he stood up to bring in his wings and change position. Jim suggested that there could be some mutual extra-pair mate attraction going on between Dad and the bird on the branch, creating an interesting mixture of aggressive and compatibility behaviors (soft vocalizing=compatibility, while threat-bout=aggressiveness). While it had never occurred to me that the two eagles might be familiar to one another, Brett also pointed out the possible familiarity of the intruder with the incubating adult. A quick search of documented nest intrusions makes it obvious that this is far from a full-metal response. Here are three aggressive reactions for comparison. Bob was quite fascinated by the second one:

• Night-time raccoon intruder (note very direct response and gaze!):
  https://youtu.be/RWJfTaO-Wz0. 
• Hawk attacks bald eagle on eggs (hawk does not survive - response and gaze are direct!):
  https://youtu.be/2s8anVG-o_I
• Bald eagle attacks owl for trying to take over nest (owl survives and is chased off):
  https://youtu.be/B0eaDz1noRg

Jim went on to provide an alternative interpretation of the interaction.

"An alternative interpretation might be that there is a conflict between opposing behaviors, such as aggression toward the intruder in conflict with, or inhibited by, a higher drive that results in priority on protecting the egg (against either the outsider or accidental damage by the parent itself if it were to move around too much near the egg, as in the behavior of balling of the feet when moving around the egg). All of this is stereotyped action patterning that has been shaped by eons of evolution. The interactions have likely happened many times ancestrally with selection of survival and reproduction producing the optimal solution of trade-offs.

Contributing to all of this is the fact that the perched outsider, younger bird, isn't making moves toward the incubating adult and also not staring at it, but just mostly looking away ... as if they're familiar with each other, or that any serious interaction occurred earlier and have now run their course so we're just seeing the end of it.

All in all, it somewhat reminds of the reduced level (to my Ontario and previous MN experience) of aggressive interactions that I observed among close nests when we were doing the FWS aerial monitoring surveys along the Mississippi River in 2009. We might be seeing a new social order in eagles! (Or, at least new to us, behaviors that are more likely elicited in a new [to us] high-density eagle population [and high productivity of prey base, so food shortage is not a factor].)"

In short, what looked to our eyes like an aggressive interaction was not really very aggressive. Dad didn't challenge the intruder with a direct gaze, loud vocalizations, or an attack. He might be familiar with her (and possibly even attracted to her), or an aggressive response might have been inhibited by a higher priority to protect the egg. The intruder also wasn't aggressive. While she remained near the nest, she didn't try to enter it or engage Dad directly, and Mom displaced but didn't seriously attack her when Mom arrived at the nest. While we think of bald eagles as being non-social on their breeding territories, their interactions with and signaling towards visitors and 'neighbors' may be more complex than we initially thought, especially as the population becomes more dense and interactions become more common.

Many thanks to Jim and Brett for sharing their experience, wisdom, and insight!

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I became curious about eagle-to-eagle interactions after reading Jim and Brett's comments. A few videos:

• Sub-adult chased off by juvenile. This is an aggressive interaction, although no physical contact occurs. Note the loud vocalizing and direct attack: https://youtu.be/vnu0ZEJEAJw
• Adult to sub-adult interaction. Another aggressive interaction. Note that eagle on the nest doesn't stand up to defend until physical contact is imminent, perhaps lending support for Jim's idea that aggressive responses might be inhibited by a higher priority to protect eggs.
  https://youtu.be/9VdEmxLgPGo
• Adult to sub-adult interaction. This is interesting and not especially aggressive, although it includes physical contact. The adult (the video identifies it as male Romeo) is watching something outside the nest. At 3:34, a sub-adult eagle lands in the nest. Romeo flaps at it, but it looks down and away without responding directly to him. For the most part, the two eagles avoid direct eye contact. At 5:31, the sub-adult appears to check out the adults talons. The sub-adult nips at the adult at 5:34 and the adult flies off. https://youtu.be/_7BssmkllQY

We are sure people are curious about whether or not the intruder could be offspring from a previous year. We can't dismiss it, since eagles are philopatric, but we also can't confirm it. Perhaps further research will shed light on the relationships between bald eagles and sub-adult offspring. 

A report: The DNR's proposed ban on non-toxic shot in Farmland WMA's

I attended the Minnesota DNR's non-toxic shot informational meeting last week and heard testimony supporting and opposing the DNR's ban on non-toxic shot in Farmland WMA's in Western Minnesota. I provided my own testimony supporting the ban as a private citizen, although in the interest of full disclosure, I identified myself as working for the Raptor Resource Project. It was a fascinating meeting! The people who supported the ban were a very diverse group that included hunters, biologists, representatives from conservation and hunting-positive organizations, private citizens, and a gun range owner. An opinion piece on the issue by long-time supervisor of the DNR's non-game wildlife program Carroll Henderson can be found here: http://soarraptors.org/2016/03/op-ed-piece-from-carroll-henderson/.

While the DNR received many more letters supporting than opposing the ban, the issue is far from settled. Minnesotans, you can email comments to steve.merchant@state.mn.us.  You may also submit written comments to the Minnesota Department of Natural Resources by mailing a letter/statement to:

Minnesota Department of Natural Resources
Non-Toxic Shot Comments
500 Lafayette Road, Box 20
St. Paul, MN 55155-4020

Be sure to reference the March 10, 2016 non-toxic shot informational meeting.

Lead is toxic
Over and over during the process, I heard that the argument against lead shot was based on faulty science. That is not the case. A few links:

• The National Wildlife Health Center: http://www.nwhc.usgs.gov/disease_information/lead_poisoning/
• The National Institute of Environmental Health Sciences:
  https://www.niehs.nih.gov/health/topics/agents/lead/
• Save our Avian Resources: lead in the environment
  http://soarraptors.org/lead-in-the-environment

We have safe alternatives
We have affordable, safe alternatives to lead shot and tackle.  In 1991, the US Fish and Wildlife Service banned lead shot in waterfowl hunting. A survey of ducks on the Mississippi Flyway found that the ban on lead shot reduced lead poisoning deaths of Mississippi Flyway mallards by 64 percent, while overall ingestion of toxic pellets declined by 78 percent over previous levels. By significantly reducing lead shot ingestion in waterfowl, the ban prevented the lead poisoning deaths of approximately 1.4 million ducks in the 1997 fall flight of 90 million ducks. 

Did the ban on lead shot prevent successful waterfowl hunting? No. The total number of geese and ducks harvested nationwide declined steeply beginning in about 1984, but started rising again in roughly 1992, as shown by this chart: http://flyways.us/regulations-and-harvest/harvest-trends. Save our Avian Resources has an excellent page on the issue: http://soarraptors.org/hunt-and-fish-lead-free/

Can you buy non-lead shot affordably? Absolutely. Cabela's has a non-toxic catalog, Clark Armory sells non-toxic alternatives only, and California has a long list of certified non-lead ammunition: https://www.wildlife.ca.gov/Hunting/Nonlead-Ammunition/Certified.

What about population impacts?
Why wait for population impacts? We know lead is toxic to us and to wildlife, and it is far more expensive to return and restore species than to provide them protection in the first place. It is something we can and should do. We would have saved a lot of time, money, and wildlife if we had tackled DDT earlier.

This is not about controlling guns or gun ownership. We aren't anti-gun, anti-sporting, or anti-hunting. Just anti-lead.

Thanks to Kay Neumann from Save Our Avian Resources and Dr. Pat Redig for all their work and research on this issue. They are truly leaders in this area! Thanks to the late Bob Anderson for doing so much to raise awareness of this issue among his friends and fans. 

Will the nest trees hold N2B and the Decorah North Nest?

We're getting some concerned questions about the strength of the trees that N2B and especially the Decorah North Nest are sitting in. The North eagles have an extremely large nest by any measure, with an estimated total area of 49 feet and and an estimated weight of around 2100 pounds. Will the trees be able to handle it?

The likelihood of any given tree or branch to break depends on its strength, its size, its shape, its health, and its location, all which affect its capacity to withstand loading by things like wind, ice, and bald eagle nests. In general, thicker trees are stronger than thinner trees, balanced trees are stronger than top or side heavy trees, healthy trees are stronger than sick or dead trees, and trees composed of dense or heavier wood are stronger than trees composed of lighter wood. Location can impact a tree's exposure to lightning and affect how it grows in the presence or absence of light and prevailing winds.

Let's take a look at the strength of five trees: a white oak (the Decorah North Nest), an eastern cottonwood (the Decorah Original Nest), a loblolly pine (bald eagles nest in lobolly pines), a sugar maple, and a shagbark hickory. A few terms before we get started:

• Specific Gravity: Specific gravity measures the density of a material. In general, the higher the specific gravity, the denser and stronger an object is. However, other mechanical properties also influence a tree's strength.
• Modulus of Rupture, or MOR: MOR is a measure of the maximum bending load in a material just before it yields or ruptures. 
• Modulus of Elasticity, or MOE: MOE is a measurement of stiffness that determines a material's deflection from a load.
• Toughness and Hardness: Toughness is the ability of a material to absorb energy and plastically deform without fracturing, while hardness measures the force required to embed an 11.28 mm (.444 in) steel ball into wood to half the ball's diameter. These two characteristics are often inversely correlated in trees: that is, a hard tree can be less tough than a weak tree. However, toughness is often proportional with density, and trees create areas of denser wood where needed. More on that later! 

Wood Species	Specific Gravity*	Bending Strength (MOR)	Stiffness (MOE)	Hardness
	kg/m3	MPa	GPa	lbf
Shagbark Hickory	0.72	139.3	14.90	1,880
Oak, White	0.70	102.3	12.15	1360
Sugar Maple	0.63	109.0	12.62	1450
Loblolly Pine	0.47	88.3	12.30	690
Cottonwood	0.36	58.6	9.45	430

Trees experience dynamic and static loading. Static loads are long-term and don't change quickly. Think of growing limbs or a bald eagle nest. Both of these things place a load on a tree, but they happen slowly and the tree has time to respond to them. Dynamic loads like wind gusts occur immediately and unpredictably, giving a tree no time to respond. Think of N2 - a healthy tree! - snapping during a storm in July 2015.

MOR describes the maximum amount of load that can be placed on a tree before it breaks, while MOE measures its resistance to being deformed elastically. Think of climbing a tree. When you step on a branch, it might bend, but unless you exceed MOE, it will snap back into place once you take your weight off. If you exceed MOE but not MOR, the branch will stay bent once the weight is removed. If you exceed MOR, the branch will break. I hope you are holding on tightly to something else!

Also keep in mind that the measurements for MOR and MOE are mega- and giga- pascals respectively. A pascal is one newton per square metre, or the force needed to accelerate one kilogram of mass at the rate of one metre per second squared. While some of these trees are stronger than others, a lot of force is needed to rupture or displace any of them! A cottonwood has the lowest MOR, but it would still take 58.6 million pascals to break it. That's a lot of static force! The DNN nest might be large, but a sturdy white oak is more than capable of supporting it. If I'm doing the calculation correctly, the weight of a roughly 2000 pound nest converts to 8825 newtons, or .008 MPa, which is nowhere near the weight or force needed to cause static rupture in any of these trees, assuming that they are healthy and the nest is relatively well balanced.

Like people, trees grow and change throughout their lives. Stress effects wood growth or build up: the more stress or compression there is on an area of a tree, the more wood will build up there to counterbalance it, toughening that area of the tree and expanding and pushing back in the opposite direction of the compressive force. You can sometimes see this on the underside of large tree limbs and you can clearly see it in cut wood. Naturalist Bernd Heinrich writes: "In tree limbs the greatest stress occurs in the “hinge” area, at the attachment to the tree. It is here that the growth rings of limbs are thicker on the bottom than on the top. A mechanism of selective wood deposition could help to brace the limbs up laterally." If we sawed through the limbs that supported N2, we might find that they were thicker and had a different pattern of deposition than similar limbs that did not support bald eagle nests. As the tree grows, it responds to the weight of nests and branches by piling on more wood where it is needed - and trees overbuild to begin with!

Of course, limbs and trees do sometimes break. However, bald eagles have a remarkable record of success when it comes to choosing trees.  One study found that, of more than 10,000 bald eagle breeding attempts that were monitored in Virginia since 1962, only one in 850 failed due to tree loss. Nearly half of these losses were due to violent storms that snapped off live trees during the nesting period.  Of the remaining losses, nearly all were in trees that had been dead only one year.

So do eagles somehow know where to place a nest for strength and balance, or is it not possible to begin a nest anywhere that isn't well balanced already? The more questions I ask, the more questions I have! But either way, bald eagles are master builders and the trees we have nests in are more than strong enough to hold them!

Bald Eagle nest in East Central Minnesota

This bald eagle nest is located in a tree about 12 miles from my house. As you can see, it is a big nest in a small tree! Bald eagles have occupied it for roughly four years. During that time, the tree has responded to the weight by deforming and thickening. I suspect this tree will go down some day in a storm, since it is more prone to succumbing to dynamic loading given its top heaviness. However, this photo gives us a great look at just how strong trees really are.

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Things that helped me learn and write about this topic:
This was the most technically difficult subject that I have ever written about. Wood strength and qualities are measured in many different ways, boards are not the same as live trees, and even arborists and horticulturalists think about and measure trees in various ways. Since trees are alive, they also aren't as uniform as, say, a nice pine 2x4. I found all of the articles I read to be fascinating (except the ones I couldn't understand at all) and they helped me to garner a whole new measure of respect and appreciation for the trees that surround us.

• Bernd Heinrich: The Trees in My Forest. This should be required reading in high school. It is available via Google Play.
• Center for Conservation Biology: Eagles Rarely Gamble During the Breeding Season 
• A nice general article on trees: Tremendous Trees
• Static Load Tests in Arboriculture. Note 'Tunnel effects' on page three. After N2 went down, a number of local Decorah people told us that slots and canyons in the valleys around Decorah produced odd wind effects.
• Ken James, University of Melbourne, Australia, Dynamic loading of trees
• American Cutting Edge: Hardness versus Toughness
• The Wood Database. What a cool website! There is more to learn about wood than I ever suspected!
• The Workshop Companion. Great reference site for woodworkers.
• Dr. Kim D. Coder, Warnell School of Forest Resources, University of Georgia, Elastic Limit: The strength properties of living trees