Eggs and Cold Weather

Mom with eggs on February 26, 2014

Everyone is worried about the eggs in Decorah. Iowa is facing extremely cold temperatures in the weeks to come. While there have been other cold years – 2008, for example, had sub-zero temperatures into early March – this looks like one for the record books. We can’t guarantee that the eggs won’t freeze, but I thought I’d talk a little bit about eggs and cold damage.

Much of what we know about eggs and temperature comes from incubationists, or people who incubate eggs. Temperature, humidity, and regular turning are all important to insuring an embryo’s survival and eventual hatch. In 1969, H. Lundy identified five temperature zones characterized by their effect on the developing embryo. These studies were carried out on chicken eggs in an artificially controlled environment, but we can look to them for some idea of how the eggs in Decorah and elsewhere might respond to ambient temperature.  The five zones are:

• The zone of heat injury or death:  Above 104.9°F or 40.5°C.
• Optimal temperature, aka the zone of hatching potential: 84.5° to 104.9°F or 35 to 40.5°C. The American Eagle Foundation lists this temperature as 99° for bald eagle eggs incubated in an artificially controlled environment.
• The zone of disproportionate development: 80.6 to 95°F or 27 to 35°C. Embryos in eggs that spend too much time in this zone can develop unevenly, leading to crippling injuries or death. Successful hatching is greatly reduced.
• The zone of suspended development: 28.4 to 80.6°F or -2°C to 27°C. Eggs at this temperature don't develop at all. Freshly laid eggs can spend a lot of time at this temperature with no harm to the egg or embryo. 
• The zone of cold injury or death:  Below 29°F or -2°C. Although eggs contain a great deal of water, they can get colder than 32°F/0°C without freezing. However, eggs that reach 29°F will freeze, which usually causes death. Some exceptions to this rule have been recorded in Mallard ducks.

So what does it all mean? 
In the last couple of days before egg-laying, we watched Mom and Dad build a wonderful nest bowl or cup of soft dry grass and shredded cornstalks. The grass conforms to the eggs, wrapping around to provide warm, dry insulation below and around them. Mom and Dad transfer heat from their bodies and regulate temperature by alternately sitting on or standing away from the eggs. Of course, this year has been cold enough that they’ve spent very little time standing. Sitting low in the nest helps keep the eggs and incubating parent warm. One of our facebook fans compared it to Tupperware – a great analogy, since the eggs are cupped below and sealed above. We've also watched the eagles bring in extra cornhusky insulation this year, building their pile as the cold deepens. The eagles may be on to something, since in 2009 the US Department of Energy awarded $200,000 to Husk Insulation, a company that makes insulation from cornhusks. The  company's panels are 10 times more effective than conventional insulators like foam.

So how warm are Mom and Dad? In a study of overwintering bald eagles, Mark Stahlmaster found that adult bald eagle average body temperatures ranged from 102.2°F, or 38.9°C, to 106.1°F or 41.2°C. Ambient temperature, wind, precipitation (snow can be insulative, but rain is not), shelter, and time of day all had an impact on body temperature. Since the zone of heat injury can be lower than the body temperature of an incubating adult, it’s easy to see why Mom and Dad might (in warmer weather) spend time away from their eggs. Although Dad has taken his share of egg duty this year, I wonder if larger Mom might spend more time incubating in extremely cold weather or at night, when eagles can drop their body temperature to reduce energy loss. Larger animals have an easier time conserving heat, since they have lower area-to volume ratios. While Mom isn’t that much larger than Dad, it might make all the difference in a cold weather event.

Lundy’s work was based on artificial incubators, where temperature and humidity can be tightly controlled. Mom and Dad live in the real world, subject to real weather events. Yet they have an excellent record of hatching eggs. Can we guarantee that the eggs won’t freeze or suffer cold damage? As much as we’d like to, we can’t. But Mom and Dad are diligent, experienced parents with a well-built nest cup, a long-term territory, and a good food supply. They are spending a lot of time clamped down on their eggs, applying heat from their very warm bodies directly to the eggs. Unlike us, they don’t need an instruction manual to provide information about temperature regulation, egg-turning, or care. We are watching and hoping for the very best. Go Decorah Mom and Dad!

PS: Sherri Elliott has mentioned the difference in the egg ‘line-ups’  - Mom incubates the eggs in a triangular pattern, while Dad incubates them in a straight line. This almost certainly has to do with the size difference between the two (and the overall area of their brood patches), although ‘shapes’ are not uncommon. Like sitting and standing, shapes and positioning can help regulate temperature and keep eggs alive.

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Resources

Stalmaster, Mark V., and James A. Gessaman. "Ecological energetics and foraging behavior of overwintering bald eagles." Ecological Monographs (1984): 407-428.

Incubation zones: Brinsea Incubation. Check them out for incubators, hatchers, brooders, and information:
http://www.brinsea.com/

Cornhusk Insulation: http://www.newscientist.com/blogs/shortsharpscience/2009/05/insulation-made-from-corn-wins.html

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Did you know?

Some birds incubate eggs by burying them in mounds. Meet the Megapodes! http://en.wikipedia.org/wiki/Megapode

Courtship, copulation, eggs, and other things romantic

Valentine's Day is here and we're all awaiting the first egg in Decorah. Given that the day is a celebration of things romantic, we thought we would discuss copulation, fertilization, and other egg-related subjects.

Courtship

The video below shows Mom expressing interest in Dad. She twists her tail feathers to the side while vocalizing and rubbing against Dad. In Decorah, courtship activities begin in late fall. Mom and Dad bring sticks and branches into the nest, eventually adding soft nesting material as courtship deepens. Food is (often) shared. The eagles vocalize together and spend more time in close proximity, moving from sitting side by side to gently pecking and footing, wing and tail brushing, and body rubbing with tail twisting and vocals. Mom is letting Dad know in no uncertain terms that she is receptive and ready for copulation. A few people have commented on Dad's 'shyness'. While this is pure speculation, female eagles are larger and stronger than males. Perhaps males want to be absolutely certain females are receptive before getting too close.

Video: Mom expresses interest in Dad


Bald eagles and peregrine falcons are both birds of prey, but they have slightly different courtship rituals. In both species, the male brings food gifts and both sexes engage in nest-preparation activities. But peregrine falcons incorporate bowing, and bald eagles don't. The video below shows peregrine bowing, which starts around 28 seconds. We should start to see this courtship behavior sometime in mid to late March.

Video: the male falcon bowing

Copulation

Male eagles, like most male birds, lack an external phallus. Bald eagles mate by touching or pressing cloaca together - the famous 'cloacal kiss'. The female perches and tilts forward, allowing the male to land with his feet lodged on her back. She twists and moves her tail feathers to one side so the mounted male can press and twist his cloacal opening around her cloaca, passing sperm from his cloaca to hers. Intense and rapid vocalizations will precede and accompany their mating. As we’ve seen in Decorah and Fort St. Vrain, mating is brief, intense, and takes place fairly frequently while the eagles are in season.

Video: Eagle copulation at Fort St. Vrain

Eggs!

So we've gone through courtship and copulation. Now the sperm needs to reach the female's ova at the infundibulum, or site of fertilization. The female is regularly ovulating, but sperm needs to be there when an ovum arrives. If sperm are too early, they will die prior to the arrival of an ovum. If sperm are too late, they can't penetrate the eggshell layers that form around the ovum in the female's oviduct. So how can fertilization be assured, assuming both eagles are fertile?

• Copulate regularly. Regular copulation helps assure a good supply of sperm - especially important in an animal that regularly clears its cloaca when eliminating waste!
• Store sperm. Sperm storage tubules maintain sperm viability, prevent stored sperm from being ejected, and continuously release sperm to the infundibulum.
• Concentrate sperm at the infundibulum. Released sperm are passively carried to the infundibulum. Their continuous release and relatively slow drift help ensure that sperm are present when an ovum arrives. 

Let's assume that sperm has reached the infundibulum and found a fertile ovum, yolk erupted, waiting for fertilization. Once a sperm fertilizes the yolk, the outer egg membrane seals off the fertile egg, which prevents further sperm entry. The egg begins to drop through the oviduct, a process that lasts for two or more days. As the egg descends, it is coated in layers: eggshell membranes, cuticle layers, and finally the outer crystallization membranes that form what we think of as the eggshell. Viola - a fertile eagle egg ready for laying and incubation!

Video: An egg's journey

Although we don't know exactly how long egg-laying occurs after mating, it is generally believed that female eagles lay eggs 5-10 days after a successful mating takes place. Since love is clearly in the air at the Decorah nest, we shouldn't have to wait too long.

Have a happy Valentine's Day!

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References

Raptor Research and Management Techniques, 2007
Raptor Research Foundation
Edited by David M Bird and Keith Bildstein
http://www.raptorresearchfoundation.org/publications/techniques-manual

Blog by David Hancock:
http://www.hancockwildlife.org/article.php/EggsEgg-WhenAndHowTheyDevelop

Do Bald Eagles Mate in Flight?

Do bald eagles mate in mid-air? Do bald eagles mate through their feet? We’ve been asked those questions on facebook, via email, and at Ustream.  The short answer? No. Bald eagles do not mate with their feet or during ‘nuptial flight’. They mate by touching cloacae – the cloacal kiss – while perched securely on a tree limb or in the nest. The male mounts the female’s back, twisting his tail under hers. The two press their cloacae together and sperm passes from his cloaca to hers. As we’ve seen in Decorah and Fort St. Vrain, mating is brief, intense, and takes place fairly frequently while the eagles are in season.



Most readers have probably heard of the bald eagle’s whirling nuptial flight. Mates or courting pairs lock talons and whirl through the air, disengaging before they hit the ground. Writers have suggested that this particular courtship activity might prove flight skill, test pair commitment, and/or arouse the eagles to begin mating. While these are lovely ideas, reality is much more complicated. Courting eagles do lock talons and whirl, but so do immature eagles, adult/immature eagles, and adult eagles who (presumably) aren’t courting.
Brett Mandernack, the biologist at Eagle Valley, suggested that immature eagle talon locking and whirling flight might be a precursor to adult courtship behavior.  While some locking and whirling appears to be antagonistic in nature, like the two adult eagles who crash-landed in Duluth in May of 2013 (http://www.usatoday.com/story/news/nation/2013/05/14/eagles-crash-land-minnesota/2159079/), some is not. Brett has watched territorial adults repeatedly lock talons and whirl, separating before hitting the ground and soaring upward to lock talons and whirl again. “Why,” he asked “would mated adults keep locking and whirling if the behavior was solely antagonistic?” Eagles display remarkable plasticity, varying their behavior in response to environmental changes, including the presence of other eagles. Perhaps talon locking and whirling flight can be made to serve a number of purposes, including courtship. Only the eagles know for sure.



We know that eagles who retain a nesting territory and partner are more productive than those that don’t. But to get to that point, an eagle must first settle in a particular area (probably not too far from its own birthplace), establish a nesting territory, and acquire a mate. Soaring displays and vocalization might help an unpaired eagle attract a mate (look at me!) and demonstrate territorial occupation (this is my place!). Talon-locking followed by whirling flight might provide a non-aggressive response to a potential partner, indicating serious interest. If the eagles pair, food gifts and other courtship activities will quickly follow.

In Decorah, courtship activities begin in late fall. Mom and Dad bring sticks and branches into the nest, eventually adding soft nesting material as courtship deepens. Food is (often) shared. The eagles vocalize together, spend more time in close proximity, and gently peck and foot to indicate their interest in one another. In late January or early February, all of this activity will culminate in copulation, with egg-laying beginning roughly 2 weeks later.

Lake Pepin is a great place to watch eagles soar and talon lock. Go the National Eagle Center’s website for more information about eagle watching on the big lake: http://www.nationaleaglecenter.org/

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Sources

Personal Communication, Brett Mandernack

Interactive Behavior among Bald Eagles Wintering in North-Central Missouri
Curtice R. Griffin
The Wilson Bulletin, Vol. 93, No. 2 (Jun., 1981) , pp. 259-264
Published by: Wilson Ornithological Society
Article Stable URL: http://www.jstor.org/stable/4161465

Lifetime Reproductive Success of Bald Eagles in Northern California / Éxito Reproductivo de Haliaeetus leucocephalus en el Norte de California
J. Mark Jenkins and Ronald E. Jackman
The Condor , Vol. 108, No. 3 (Aug., 2006) , pp. 730-735
Published by: University of California Press on behalf of the Cooper Ornithological Society
Article Stable URL: http://www.jstor.org/stable/4151094

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Did you know?

Scientists discover the genetic reason why birds don’t have penises
http://www.smithsonianmag.com/science-nature/scientists-discover-the-genetic-reason-why-birds-dont-have-penises-94130874/
Note: This is a pretty frank discussion that includes a video. 

Does Bad Weather Affect Bald Eagle Egg Laying?

April 20th, 2011: Spring Snowstorm

Facebook fan Dianne Wisse asked the following question about the Decorah Eagles: "With the extreme winter weather predicted to continue and even worsen--more 'polar vortex' cold, snow and dangerous high winds--is there any chance it will affect Mom/Dad Decorah's chances of laying viable eggs, or might nature step in to prevent the loss of eggs/eaglets to the unusual weather?"

We didn't begin tracking the eagles egg-laying schedule until 2009. It is as follows:

• 2013: Egg laying unknown. Hatch believed to have started on 3/25/2013
• 2012: Egg laying began on 2/17/12. Hatch began on 3/27/2012
• 2011: Egg laying began on 2/23/11. Hatch began on 4/01/2011
• 2010: Egg laying began on 2/25/10. Hatch began on 4/03/2010
• 2009: Egg-laying began on 3/02/09. Hatch began on 4/09/2009

2013 was, like 2014, cold and snowy. 2012 was unusually warm, although the first half of 2011 was 'on the cool side', according to the Iowa Department of Agriculture. If weather impacted the timing of egg-laying, we would expect egg laying to happen a little later in cold,snowy years. But that's not what happens. Instead, Mom lays eggs a little earlier every year, regardless of the weather. 

I did a little reading about the regulation of bald eagle reproductive rates. In a study of bald eagles in southeast Alaska, researcher Andrew J. Hansen found that breeding activity is related to food abundance and habitat quality. He wrote: "Laying date was influenced by proximity to spring food supplies. Pairs nesting within 3 km of food patches laid eggs earlier than those nesting farther from food clumps." Hansen also found that laying date was advanced - that is, it happened sooner - where food was abundant. He believed that earlier laying was probably advantageous, since juveniles that fledge earlier have more time to acquire the skills required for surviving harsh weather and unpredictable food supplies. 

So cold and harsh weather don't influence egg-laying dates directly. But both can influence food availability, which does. During extremely cold and snowy winters, rodents might remain concealed under thick snow pack, fish and fish carcasses might be sealed under ice, and roadkill might be plowed under snow drifts, unavailable until the snow melts. In years where food is scarce, egg-laying happens later. If food can not be obtained, the nesting territory might be abandoned altogether. 

Fortunately, the Decorah eagles have an abundant and highly available food supply. It includes dead and live trout from the nearby hatchery, suckers and other fish from the creek, animals attracted to the 'food oasis', pigeons and other non-migrating birds that live in the area, and road kill. The eagles also have a lot of experience living here - they know their territory and its seasonal rhythms very well. The abundance and reliability of their food supply allows Mom to lay eggs a little earlier than she might otherwise. Experience might be the reason her laying date has crept up since we began keeping track in 2009.  

So in short, I don't expect her to lay egg #1 later significantly later than she has the past few years, although I'm not willing to predict a date. We've seen Mom gently footing and pecking Dad, and both eagles have increased their visits to the nest. Watch for copulation - that will help us estimate a time frame!

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References

Regulation of Bald Eagle Reproductive Rates in Southeast Alaska
Andrew J. Hansen
Ecology , Vol. 68, No. 5 (Oct., 1987) , pp. 1387-1392
Published by: Ecological Society of America
Article Stable URL: http://www.jstor.org/stable/1939222

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Did you know?

Latitude also influences nesting chronology. From the US Fish and Wildlife Service:

• In the Southeastern US, egg-laying can begin in mid-to-late October
• In the Chesapeake Bay region, egg laying can begin in mid-January
• In the Northern US (including Iowa) and the Pacific region, egg-laying can begin in late January
• In the Southwestern US, egg-laying can begin in late December
• In Alaska, egg-laying doesn't start until the beginning of April.

Follow this link to learn more. The nesting chronology is on page 6.

For more on eagles and cold weather, follow this link: http://raptorresource.blogspot.com/2014/01/eagles-and-cold-weather.html

Eagles and Cold Weather

-13F in Decorah at 1:54pm on January 6, 2014. Yikes!

We are getting a lot of questions about Mom, Dad, and cold weather. I've written about feathers and weather, but overwintering bald eagles also protect themselves by maximizing energy gain and minimizing energy loss. Every calorie is made to count.

Maximizing Energy Gain
Bald eagles maximize energy gain during periods of cold stress by foraging in groups, gorging food, and assimilating more energy. As we know from watching Mom and Dad, some eagles remain on their territory year round. But many others leave their territory to roost communally during the winter, especially along stretches of open water. Communal roosters often forage in smaller groups of less than 20 eagles, increasing the likelihood they will find food with less energy expenditure than if they hunted alone. Bald eagles also steal prey from other eagles and birds (kleptoparasitism), an optimal behavior, at least during periods of food scarcity, for animals that forage together. When one bird finds food, all of them exploit it. This social behavior increases efficiency and decreases energy stress.

Mom and Dad don't communally roost, and we don't know whether or not they forage with other eagles away from their home territory. The abundant, high-quality food provided by the trout hatchery, stream, and road may be an important enticement to stay on territory year-round. However, Mom and Dad are probably gorging the food they find. This helps them calorie load quickly, reduces the amount of time they need to spend looking for food, and helps prevent food stealing. The more quickly an eagle eats its food, the less likely it is something else will steal it!

Finding food extracts an energy cost, so Mom and Dad need to make the food they find count! During periods of cold stress, bald eagles assimilate more food energy than they would otherwise. This may be because in extreme cold weather, blood flow is decreased to the skin and extremities and increased to the visceral organs, including the stomach. Greater blood volume in the alimentary tract might increase digestion of food, leading to greater assimilation of food energy when the eagles need it most. A similar mechanism has been found in snowy owls, who live and hunt in even colder weather.

Minimizing Energy Loss
Bald eagles minimize energy loss by becoming sedentary, seeking protective microclimates, reducing night-time body temperature, and reducing foraging costs.  This time of the year, we don't see Mom and Dad at the nest as often during periods of extreme cold. Flying, stick procurement, and nestorating all have a high energy cost, and overwintering eagles need to minimize energy loss. So what are Mom and Dad doing right now? Probably nothing at all. In extreme cold, minimizing activity maximizes fitness.

When overwintering eagles do fly, they don't tend to make long trips. They also seek protective microclimates. Needled conifers hold more heat than leafless deciduous trees, so Mom and Dad might seek shelter in a pine grove. There may also be some sun-warmed, wind-protected pockets next to the bluff, or some protected space between the trout hatchery buildings and the bluff. These areas will reduce wind exposure and hold heat more efficiently, which helps the eagles minimize energy loss. Like mammals, birds are endotherms - that is, they maintain an internal body temperature. Maintaining body temperature takes energy, so anything that helps an eagle maintain its temperature reduces energy loss.

Although eagles are endotherms, they don't have to maintain a given body temperature all of the time. 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. Mark Stahlmaster estimates that this saves about 4.6% of an eagle's daily energy budget - a very big deal during periods of cold stress. Once again, we see Mom and Dad doing more by doing less.

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://www.dnr.state.mn.us/birdfeeding/winter/index.html

For more on feathers and weather, read this blog post: http://raptorresource.blogspot.com/2012/02/it-was-hard-not-to-feel-sympathy-and.html

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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
Article Stable URL: http://www.jstor.org/stable/1942594

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
Article Stable URL: http://www.jstor.org/stable/3808555

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

Kleptoparasitism: http://en.wikipedia.org/wiki/Kleptoparasitism

Birds and Daylight Length

Dad makes a scrape in the snow

Many animals and birds react to daylight length. This phenomenon, known as photoperiodism, allows their physiology and behavior to adapt to seasonal changes in the environment, and indicates the most favorable time of year to produce offspring. Although bird species vary in their responses, the annual cycle of birds overall is driven by daylight length.

How do birds detect changes in day length? Like many other creatures, they use photoreceptors – specialized cells that detect light and initiate a physical response to it. The photoreceptors in birds are not in their eyes (as they are in mammals like us), but deep in the brain, in an area called the ventromedial hypothalamus. The receptors react to light that penetrates birds’ thin skulls and surrounding tissues. Changes in day length (and possibly strength and angle, at least in non-equatorial latitudes) initiate major changes in birdie physiology and behavior.

To quote Scott Weidensaul, "Changes in the photoperiod pull many strings in a bird's body".  As daylight length grows longer, the gonads of birds grow larger and produce more sex steroid hormones. This stimulates changes in behavior and sometimes plumage: depending on the bird, it may grow colorful plumage, choose and defend a territory, spend time vocalizing and flying to attract a mate, and engage in nest building. The Decorah eagles will begin rapidly responding to day length now that we are past the solstice. As the days grow longer, the eagles' gonads will swell in response. They will move deeper into courtship and nest-building activities will increase in frequency, duration, and intensity. Mom and Dad will spend more time bringing in sticks for the outer cup and crib rails, and softer materials, including corn stalks, for the inner bowl. We may see scraping as Dad did today in the snow: http://youtu.be/gsTEbNRGnTw. Copulation should begin in late January to early February, followed by egg laying in mid-to-late February.

Daylight hours will exceed nighttime hours on March 20th, although the eagles will have already experienced a new set of hormonal changes brought on by egg-laying and eaglet care. After June 21st, daylight hours will begin decreasing, which will trigger another set of biological changes in many birds. By late summer and early fall, birds might begin moving away from natal or home territories, packing in calories, gathering or flocking together in larger groups, including mixed age and species flocks, and in many other ways preparing for migration and overwintering. This year's young eagles will disperse and we'll see less and less of the adult eagles until early winter, when the cycle will begin anew.

Some exploration points:

• Is there a predictable increase in frequency of nest visits as daylight length increases?
• Do Mom and Dad differ in their nest building behavior? 
• Do Mom and Dad spend more time interacting as daylight length increases?
• Does weather also appear to impact nest-building activities?

I would love to hear from any teachers that end up exploring any of these points in the classroom. Email me at ries93@gmail.com and let me know about it, or friend us and share it on our facebook page:
http://www.facebook.com/pages/Raptor-Resource-Project/103786266324668

Some reference materials:

• Living on the Wind: Across the Hemisphere with Migratory Birds (thanks, Joan!)
• Adaptation and evolution of photoperiod response systems in birds (http://www.springerlink.com/content/nx8804125624q526/)
• Explanation of the word Recrudescence (I didn’t know Senescence had an antonym!): http://en.wikipedia.org/wiki/Recrudescence
• Photoperiodism: Deep Brain Light Reception: http://www.nu-research.com/research/6169
• Photoreceptor Cell: http://en.wikipedia.org/wiki/Photoreceptor_cell

Lead Poisoning, Toxic Shot, and Lead-Free Hunting

Volunteer Ron Andrews with lead-poisoned bald eagle

On the evening of December 9, 2013, Bob Anderson of the Raptor Resource Project received a phone call about a sick and possibly injured eagle. The story of how he responded to it can be found here. Despite the best efforts of everyone involved, the eagle died of lead poisoning roughly two days after it was rescued. To quote Bob: “I have reached a point regarding these lead poisoned eagles that surprises me.  I do not get hardened and begin acceptance for picking up these sick eagles on the verge of death and clearly in severe pain.  To look at an adult bald eagle gasping for breath and making what can only be described as cries of pain; is something that never gets easy and to think it is clearly preventable.”

So how serious is lead poisoning? SOAR has wonderful information on their website at http://www.soarraptors.org/leadresearch.html. A few figures that struck me:

• 56% of all eagles admitted to Iowa rehabilitators between 2004 and 2008 had abnormal lead levels in their blood. This ranged from a low of 37.5% in 2004 (with 62.5% of eagles being tested) to a high of 70.0% in 2005 (with 90.0% being tested).
• The University of Minnesota’s Raptor Center in St. Paul received 117 lead-poisoned bald eagles during the winter of 2009.
• While lead poisoning can kill directly, as it did with the eagle we tried to rescue, lead toxicity is also a factor in collision deaths and injuries. According to the Raptor Center, about 85% of eagles that come in with collision injuries also have elevated lead levels. This video from the UK shows the effects of lead on a duck's coordination and motor skills: http://youtu.be/KaVr70-2mpc

Lead poisoning is primarily the result of exposure to leaded or toxic shot. In 1991, the US Fish and Wildlife Service banned lead shot in waterfowl hunting, although it can still be used for some other types of hunting, depending on your state's laws and regulations. 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. Requiring the use of non-toxic shot did not negatively impact waterfowl hunting, but did prevent ducks, geese, and many other animals from coming into contact with lead shot by ingesting it directly or feeding on lead-poisoned animals or carcasses containing shot.

There are alternatives to toxic shot. A few links:

• Federal Premium® Ammunition shares the history behind steel and alternative nontoxic loads. From Duck Hunters Unlimited: http://youtu.be/gOvlGWaKf9M
• Field Testing Steel Shot: http://youtu.be/5IJsdkop5Gg
• Hunting Non-Lead: A sportsmen’s website promoting non-lead hunting: http://www.huntingwithnonlead.org/index.html
• SOAR’s page on hunting lead free. SOAR has been involved in lead-free hunting for a long time: http://www.soarraptors.org/HuntLeadFree.html

There are a number of groups that advocate for non-toxic shot. The movie Scavenger Hunt chronicles the efforts of a small team of biologists and hunters to convince hunters in northern Arizona to use non-toxic shot. As the director points out, many hunters have been deeply involved in conservation efforts. This method could also provide a model for lead-reduction efforts in other places. You can watch a trailer here: http://scavengerhuntfilm.com

If you hunt or shoot, please use non-toxic shot. It does your prey well, it does you well, and it does the environment well. We aren’t anti-hunting and we aren’t anti-gun, but handling lead-poisoned eagles has made us anti-lead shot.

References

• Harvest Trends: http://flyways.us/regulations-and-harvest/harvest-trends
• Bald Eagle Lead Poisoning in Winter:  http://www.peregrinefund.org/subsites/conference-lead/PDF/0119%20Neumann.pdf 
• Notice of Waterfowl Survey: http://www.fws.gov/pacific/news/2000/2000-177.htm
• Minnesota Eagles Fall Prey to Lead: http://www.startribune.com/local/137358413.html

Websites:

• SOAR – Hunting Lead Free: http://www.soarraptors.org/HuntLeadFree.html
• SOAR – Lead Research: http://www.soarraptors.org/leadresearch.html
• MN Raptor Center: Lead Poisoning and Bald Eagles: http://www.cvm.umn.edu/raptor/MedicalServices/RaptorMedicine/LeadPoisoning/home.html
• Hunting Non-Lead: A sportsmen’s website that promotes lead-free hunting: http://www.huntingwithnonlead.org/index.html

2013 Decorah Eagle Cam Questions

We turned on the Decorah eagle cam this morning and questions are rolling in! Here are the answers to the most commonly asked questions so far:

Where are Mom and Dad Decorah nesting?
They are nesting in the new or yonder nest, henceforth to be known as N2. N2 is about 533 feet or 162 meters east of N1, by the side of Trout Creek. It is 60-70 feet up in the center fork or crotch of a cottonwood tree. The image below shows both nests and the trout hatchery.

N1 and N2. The eagles are currently nesting in N2.
Click the image for a larger view.

What is the diameter of N2?
We didn't measure it exactly, but it is smaller than N1. I'd guess about 4 feet in diameter. This yields a circumference and area of about 12.5 feet. Neil and I were just barely both able to fit into it, and we hung all of the equipment of the side with leashes and anchors.

How deep is N2?
Another estimate. I'd say 3 to 3.5 feet. It was much easier to climb into than N1.

What types of trees did they raid for the railings?
The available kind. Primarily cottonwood, judging from the trees surrounding it. The neighborhood also contains maple and oak, but cottonwood is the predominant tree.

How would you describe the tree trunk joining where N2 is?
N1 was out on a limb, away from the central fork of the tree. N2 sits directly in the tree's center fork or crotch, where the trunk splits to form smaller branches.

How many corn husks were in it when you put up the cams?
None! We installed the cams on August 31. The eagles hadn't yet started fall courtship or nestorations.

Did you leave a food offering when you put up the cams on N2?
We didn't. Fortunately, Mom and Dad didn't mind.

Do the cams bother them? Does the IR light bother them?
The eagles are unable to see IR light. I've got a blog post explaining it here: http://raptorresource.blogspot.com/2012/03/what-is-infrared-light-and-why-cant.html. If you don't want to read the long explanation, you'll notice that the eagles' pupils don't respond to the IR light by contracting or expanding. They can't perceive it and we wouldn't either if the camera wasn't mapping the image down into the visible spectrum for us.

The cam doesn't bother the eagles either: it is fairly small, up above them, and painted drably to stop reflection and glare. The globe is highly smoked enough that I can't see through it. If the eagles can, it is no more alarming to them than anything else - leaves blowing, branches tossing, cloud shadows, squirrels and other animals, and people on the bike path. Their world is filled with movement and sound.

Did you work on N1's cams?  If so, did you see anything that would help speculate on why they left N1?
We didn't go up into the tree - those cams are still running from 2012. We don't know for sure why they left, but there are two theories.

• Theory one: That's what eagles do. In one study of 318 eagle territories in Alaska, 45% of eagles studied had more than one nest on their territory. In another study of 924 territories, eagles were found to have an average of 1.5 nests in their breeding area. N1 was built in 2007. Maybe it was simply time for them to build a new nest. We all know how much time they spend working on the nest.
• Theory two: The old nest was built farther out along the branches of the cottonwood. Its weight was causing it to tilt toward the outside. This could have caused the eagles to abandon it in favor of a new nest. 

I'm more in favor of one, myself, but I'm not ruling out two. For more speculation, check out this blog post: http://raptorresource.blogspot.com/2012/10/the-decorah-eagles-have-surprised-us.html

Coming down the tree

How did you get into the tree?
After making sure no eagles were in the area, we fired a crossbow loaded with monofilament line over our target branch. We used that to pull a four mm cord, which was used to pull an 11mm climbing line. Neil used a frog system and I used a grigri + ascender + carabiner. Neil got up into the nest in about a minute. It took me a little longer. Here are two video links that show the basic technique:

• http://youtu.be/NJHBQVkBxj0 (grigri + ascender)
• http://youtu.be/ZTai7Gd5SaY (kroll frog system)

Coming down was interesting since Neil's rope wanted to pull him away from the tree. We wrapped webbing behind him and I pulled him into the tree so he could run the cable. This worked extremely well.

How many cams are there?
Two - one PTZ and one fixed cam. The PTZ is a mini PTZ and the fixed cam is also quite small. They are painted drably.

Where are they mounted?
The nest is cradled in the center of the tree. The limb on the south side of the trunk shoots out and up. The cameras are mounted a little over where the limb turns up. I'm guessing they are about four feet above the nest.

What kind of cams?
Despite having helped install the cam, and don't know much about them. Both were purchased from KT&C and the PTZ is a mini-outdoor cam.

How long did it take to install the cams?
Bob had everything ready to go and it went very quickly. It took about three hours from the time Neil started up his rope. We got up, installed the two cams, and rappelled down, fixing the cable as we went.

Did the eagles notice or mind?
They did not. As I wrote earlier, We installed the cams on August 31. The eagles hadn't yet started fall courtship or nestorations. The cams themselves are small and painted drably to minimize reflections or anything else that might disturb the eagles.

Red-Tailed Hawks and Social Play

Eaglecrest facilitator mochamamma has captured several videos of young red-tailed hawks squabbling, chasing, and stealing food from one another.

• Eaglecrest live stream: http://www.ustream.tv/eaglecresthawks
• Red-tailed hawks fight and chase: http://www.youtube.com/watch?v=xpL_4_xfdnI&feature=share&list=PLeNR2ocnlCOe1ME2oM1i-ixbUGV03AGiF
• Five hawks: http://www.youtube.com/watch?v=mxVug0Ackjc&feature=share&list=PLeNR2ocnlCOe1ME2oM1i-ixbUGV03AGiF
• Eight hawks: http://www.youtube.com/watch?v=XMijoLfGq-o&feature=share&list=PLeNR2ocnlCOe1ME2oM1i-ixbUGV03AGiF

At first we thought they might be nest mates – although Stitch and Spot hatched just one young hawk, there are other nests in the area. But as the hawks piled up – three, four, five, eight – it became increasingly clear they weren’t related. What was going on?

We had a couple of ideas. Eaglecrest’s pond is a hot spot for local wildlife. Well over 30 species of animals have been captured on camera, including reptiles, amphibians, several mammals, and many birds. Large concentrations of raptors have been recorded at watering holes in Africa, Australia, the American Southwest, and other arid places. The young hawks at Eaglecrest were probably drawn in from the surrounding area by the pond’s abundant food and water supplies. But are they competing for limited resources or engaging in play and social interaction? Maybe a bit of both is happening.

I tend to think of red-tailed hawks as fairly solitary creatures. They chose a mate, build a nest, and defend their territory from interlopers, including other red-tailed hawks. But researcher Charles Preston observed red-tailed hawks in winter communal roosts of four to six members. These roosts sometimes included ferruginous hawks and at least one was close to a large communal roost of bald eagles.  Red-tailed hawks will also concentrate in higher numbers based on prey availability, which is probably why I start noticing them in larger numbers mid-fall. Like many other birds, red-tailed hawks are far less territorial when they aren’t breeding, although it might be a stretch to call them social. Yet juvenile red-tailed hawks engage in social play.

Play is well-documented among juvenile red-tailed hawks. They have been observed playing with inanimate objects like rocks and sticks – stalking them on the ground, pouncing on them, and dropping and catching them in flight. Play seems to have evolved in most species that provide prolonged periods of parental care, and red-tailed hawks are no exception. As Charles Preston notes, the young birds “may gradually broaden their range of hunting methods and increase their skills by learning from their parents or other red-tailed hawks.”

The young red-tailed hawks at Eaglecrest chase one another, steal prey, and mock fight. They spread their wings, assume striking poses, mantle food, stalk through the undergrowth, and wrestle, pinning each other down before walking away. It is interesting to speculate that this ‘flocking’ behavior might help the young, inexperienced hunters capture food, even if they risk having it stolen out from under them. More eyes are more likely to find food, especially when the hunters are young and inexperienced. The sheer number of young hawks might help flush prey out, although any successful hunter will need to defend his or her dinner against the rest. Although the pond is a rich environment, the young hawks are still learning to hunt and compete for prey. A little musing: we know the hunting skills they acquire will help them procure food. Will social skills like posturing and wrestling help them acquire mates and defend territory from other red-tailed hawks?

Presumably, our hawks will spend several weeks together honing hunting, social, and other survival skills prior to dispersal (or forced eviction by adult residents). I hope the skills they have acquired through social play will help them survive.

We still don’t know how common this kind of aggregation is, although I intend to do more reading and research in the weeks to come. Is this common outside of hot spots like the Eaglecrest pond? I have no idea. More questions: we have watched young eagles and vultures play, although those birds were pre-fledging. How does pre-fledging play inform post-fledging play? How is play different and alike in different species? Do parents play with young? Why is play so prevalent in juveniles? These are worthy and important questions to ask. Even TED plays attention to the importance of play: http://www.ted.com/talks/stuart_brown_says_play_is_more_than_fun_it_s_vital.html
So get out and play! 

Golden Eagles

Eaglecrest's nesting golden eagles normally appear only at a distance. But on August 31, an immature eagle decided to show up in camera range. Viewers were treated to amazing views of the eagle's golden feathers, large talons, nictitating eyelids, and overall plumage. Video highlights can be found here:

• Beautiful golden eagle
• Golden eagle close-up
• Golden eagle looks wary
• Golden eagle looks around
• Nictitating membranes
• Plumage close up
• Talon close up
• Fly away

Golden eagles get their name from the golden or tawny wash of feathers on their head and neck feathers. Adult American gold eagles are otherwise dark (or chocolate) brown in plumage, with 'marbled' flight feathers on their wing and tail. They range from 26 to 40 inches in length. Overall size is a complicated issue - while American gold eagles tend to be smaller than their counterparts in Eurasia, the largest gold eagle ever recorded was a female banded and released in Wyoming in 2006. Although bald eagles are a little bit longer on average than golden eagles (34 inches in length versus 33 inches in length), the difference is small enough that some golden eagles will be longer than some bald eagles. Confusing the issue even further, golden eagles (unlike bald eagles) don't appear to follow Bergmann's rule: one study found that golden eagles in Idaho were larger than those from Alaska. We can confidently say that they have a larger wingspan than bald eagles: North American golden eagle wingspans range from 6 feet to 7.2 feet according to Animal Diversity Web.

The eagle's nictitating membrane protects its eye

Look at that face! The nictitating membrane found in all birds is clearly visible. This membrane protects and moistens a bird's eye while allowing it to see. It also helps protect the young eagle's eye from scratches administered by struggling prey animals. The golden eagle lacks the baffles or 'jet cones' in a peregrine's nose, probably because golden eagles don't dive as fast as falcons do. Golden eagles achieve speeds of 28-32 miles per hour in an unhurried soaring flight, although they can achieve 120 miles per hour in a fast glide, and 150 miles per hour in a stoop. Its curved beak has sharp cutting edges for tearing meat, but lacks a falcon's tomial tooth. The tomial tooth, a small projection on the outer edge of the upper mandible, allows falcons to bite through cervical vertebrae and sever the spinal column of prey, quickly dispatching it. Golden eagles, however, deal death with their talons.

Check those legs and talons out! Unlike bald eagles, adult golden eagles are 'booted' - that is, their feathers cover their entire legs down to the toes. This may help protect their legs from bites and scratches inflicted by struggling prey. Golden eagles eat more kinds of prey than I can list here, since over 400 vertebrate species have been recorded as golden eagle prey. Although golden eagles appear to have food preferences, they are highly opportunistic hunters that will predate most reasonably-sized animals. They aren't going to wait for rabbits if ground squirrels are available!

Talons. 'He clasps the crag with crooked hands...'

The long, powerful talons of the golden eagle make escape extremely unlikely once prey is contacted. They can be up to three inches long and exert approximately 440 pounds per square inch of pressure. Small prey might be crushed, while larger prey might die from blood loss, shock, or collapse of the lungs following multiple punctures. Although the argument about how much weight golden eagles can carry rages on (Teenagers! Whole cows! Adult wolves!), the general consensus among people who study golden eagles is that prey much over 4.5 pounds would need highly favorable wind conditions for lift. So if a large golden eagle had plenty of momentum, and if the wind was right, and if it was able to swoop down and catch prey in its talons without stalling out, it might be able to lift more. But how much more is a matter of debate. Very large prey is simply eaten in place.

With their short, wide tails and long, broad wings, golden eagles are built to soar. They cock their wings in a slight 'V', somewhat like turkey vultures, and hold their wing tips wide open, flapping only when necessary. Unsurprisingly, they prefer open country and like to nest up high. Jumping off something high to attain lift is much less work than dead-lifting from the ground and height may, in some cases, make it easier to get prey to the nest. At Eaglecrest, the resident golden eagles nest in a large tree. Their large stick nest (smaller than a bald eagle's nest, on average, but still pretty large) is lined with grass and other soft vegetation when in use.

The flash of white indicates an immature eagle

Golden eagles are territorial. Given that this was a juvenile (its feet were not fully booted, it reveals a flash of white at the base of its tail when flying, and it has a lot of white patches), it was most likely a 2013 fledgling that hadn't yet dispersed. Like bald eagles, golden eagles appear to disperse from the natal sites, wander (fairly) widely, and return to their natal region, if not nest, as they approach maturity. I hope our young golden eagle will survive to adulthood and return to contribute yet more magnificent golden eagles to the area. What a wonderful sight to see!

Things that helped me write about this topic:

• Animal Diversity Web - Golden Eagles: http://animaldiversity.ummz.umich.edu/accounts/Aquila_chrysaetos/
• Wikipedia - Golden Eagles: http://en.wikipedia.org/wiki/Golden_Eagle
• Pawnation - Golden Eagles: http://animals.pawnation.com/interesting-golden-eagle-1588.html
• Nature - Eagles: http://www.pbs.org/wnet/nature/episodes/eagles/introduction/3089/
• Identifying feathers: https://www.fws.gov/lab/pdfs/trail.2003c.pdf
• How to age golden eagles. Worth the read - not an easy thing to do: https://www.aba.org/birding/v36n3p278.pdf
• Nictitating membrane. I love this blog: http://www.wqed.org/birdblog/2010/03/05/anatomy-nictitating-membrane/
• The golden eagle and philopatry

Getting Wet!

We talk about weather quite a bit. From wind in the tree to ice and snow on an eagle's back, we watch birds face difficult weather conditions. As our followers know, eagles and peregrine falcons have highly insulative waterproof feathers that protect them from wet, cold weather. However, some birds specialize in getting wet.

This double-breasted cormorant was caught on camera at Eaglecrest. The cormorant is a marine bird that specializes in eating fish, although it will also sometimes eat insects, amphibians and crustaceans (thank you, Animal Diversity Web and Wikipedia). They generally feed in shallow water (less than 8 meters or 24 feet deep), which may explain why they like Eaglecrest's pond. David McDonald, Eaglecrest's owner, also keeps it well stocked with fish.

Even many waterfowl tend to avoid actually getting wet. Like many birds, ducks and geese have feathers that 'zip' together and trap air, forming a water-resistant coat of sorts. They coat their feathers with oil from their preen glands, further helping repel water. Dabbling ducks (like the mallard and wood ducks at Eaglecrest) spend most of their time on the water's surface, tipping butt-up every once in a while to nibble passing food. Wet feathers would weigh them down, causing them to ride lower in the water. This in turn would lead them to expend more energy while searching for food - a bad trade off all the way around. Dabbling ducks want buoyancy.

But the cormorant has a different hunting strategy. A cormorant's outer feathers are water permeable, which weighs the cormorant down and helps it remain underwater. There is some debate about whether this has to do with feather structure or its preen gland. Some sources claim that cormorants produce less preen oil, aiding feather permeability, while others believe that feather structure plays a more dominant role. Whatever the cause of permeability, dry feathers next to the cormorant's skin trap air. Its unique feathers reduce buoyancy while retaining warmth. For all practical purposes, the cormorant is wearing a sort of home-grown dry suit. Unlike its cousin the Anhinga, which soaks all the way through, cormorants can handle cold water. I've seen them in shallow water on the south side of Lake Superior, near the Apostle Islands, where summer surface water temperatures may not climb much above the mid-sixties - and that is in the warm part of the Big Lake! The cormorant's long tail and cyclical paddling also help reduce buoyancy. All of these things
keep the cormorant underwater longer at a lower metabolic cost, which pays off in more food opportunities and reduced energy loss.

Dabbling ducks spend a lot of time floating on the surface of the water. But once a cormorant has secured dinner, it tends to leave. It is a diver and swimmer, not a leisurely floater. It spreads its wet wings to dry until the next time it goes hunting underwater.

Some cultures fish with trained cormorants. Click here for a video that shows cormorant fishing: http://youtu.be/Me3J0K1Qd5o. Note how much lower they ride in the water even when floating. Scuba divers should check this link out - at least scuba divers that also enjoy reading about birds. This is the first time I've found a reference to Boyle's Law in a bird book. And finally, some people believe that the cormorant's wing spreading may serve social or thermoregulatory purposes as well.

Some more things that helped me learn about this topic:

• Spread wing postures: http://www.stanford.edu/group/stanfordbirds/text/essays/Spread-Wing_Postures.html
• Dabbling versus diving ducks: http://blogs.sandiegozoo.org/2012/07/18/dabbling-vs-diving-ducks/
• Cormorants and submerged swimming: http://jeb.biologists.org/content/207/12/2101.long
• Cormorants: http://www.allaboutbirds.org/guide/double-crested_cormorant/lifehistory

Kestrel Nest Box Update

The American kestrel prefers open areas with short ground vegetation such as grasslands, meadows, fields, and parks. In urbanized areas, they might be seen perched on a pole or wire overlooking open space below them. They feed primarily on small animals, including grasshoppers, mice voles, dragonflies, and small lizards. If you have suitable habitat and would like to install a kestrel nest box, click here for our plans. We'd love to hear from anyone who has installed one of our boxes, so shoot me an email and let me know: ries93@gmail.com.

Last year we began a pilot project to install kestrel nest boxes along rural gravel roads. The American kestrel (Falco sparverius) is a small falcon that is in decline throughout parts of its range. There are a number of theories about the kestrel's decline: HawkWatch International's list of factors includes development and reforestation of preferred habitats, poisoning, and the West Nile virus. We've focused on the loss of grassland in Iowa, where farms have grown larger, woodlots, fencerows, and fallow land have shrunk, and small grains and hayland have been replaced with row-cropped soybeans and corn. The Iowa DNR states:

"Between 1990 and 2010, Iowa lost 2,615 square miles of potential pheasant habitat. This habitat was a mix of small grains, hay land, and Conservation Reserve Program (CRP) acres. To put this loss in perspective, 2,615 square miles is a strip of habitat 9 miles wide that would stretch from Omaha to Davenport!" [2012 Iowa Roadside Survey]

So why use ditches? Bob looks at the ditches and shoulders of rural roads and major highways as voleways. I don't tend to think of farmland as heavily developed, myself - it's all green, right? - but mile after mile of row-cropped corn and soybeans is not a natural environment. As grassland and pothole prairie are converted into farmland, animals and birds are forced into ditches. Water, rodents, insects, and plant life attract a wide variety of larger animals, including deer, rabbits, woodchucks, gophers, mink, muskrats, badgers, fox, raccoon, skunks, snakes, frogs, red-tailed hawks, harriers, kestrels, sparrows, mourning doves, gold finches, bobolinks, and pheasants.

A kestrel in one of our nest boxes. Photo
credit Nora Hensley.

A little back-of-the-envelope calculation. Iowa contains a total of 36,016,640 acres. Over 90%, or 32,414,976 acres, is under till. So how much of what's left is ditch? That's a hard question. The DOT manages about 175,000 acres along interstate and state highways, but that figure doesn't cover county, city, and town roads. When those are added in, the total jumps up to about 1.6 million acres, or 44% of the remaining 3.6 million acres left. Although broken and fragmented, that is a lot of potential habitat with which to create a kestrel habitat.

Last fall, we installed six nest boxes along 310th street in rural Winneshiek County [click here for google map]. We returned this spring to find that two of them were destroyed. One had tipped over and the other had been vandalized. However, four were still standing and three contained kestrels! We clearly needed to add cement to the base of the poles to keep them stabilized, but other than that, the plan worked!

Bob enlisted the help of David Lynch and his wife Anne to add concrete to the base of the poles and we returned a week or so later to band kestrels. Unfortunately, we weren't able to band - in two of the three nests, the babies were too young, and they were almost on the wing in nest #3. Still, our pilot project proved that rural ditches can provide habitat for nesting kestrels. 75% of the nest boxes left standing in the spring produced kestrels, and we can avoid tipping by stabilizing the box poles with cement. A big thanks to county engineer Lee Bjerke for giving us permission to install the boxes in Winneshiek county's right-of-way.

We will be looking to expand this program in the coming year, and we would love to hear from anyone who downloaded plans and built one of our kestrel boxes. Shoot me an email at ries93@gmail.com.

Great Spirit Bluff Peregrine Falcon Update

By now most of you are aware that all four young falcons jumped from the nest box at Great Spirit Bluff on June 17th. They were approximately 10 days away from fledging. Searchers were only able to find one of four falcons. Bob evaluated Jonathon, a male, and decided to augment/foster Jonathon into another nest box rather than risk having him jump out again. He chose Red Wing Grain as the new site, since the two young falcons there are about the same age as Jonathon. We fostered Jonathon on the morning of June 19th and he seems to have adapted quite well to his new surroundings. 

We chose not to continue the search after the first night. Like many young animals, the falcons either hide or try to scurry under cover when they hear threats approaching. We didn't want to drive them so deep in into the undergrowth that Michelle and Travis couldn't reach them. Since then, we have heard the young falcons calling from the area below the nest box, and we have witnessed Michelle and Travis carrying what appears to be prey down below. We hope to see the young falcons at the nest box or on the ledge again, but only time will tell. 

We have received numerous questions regarding the nest box at Great Spirit Bluff. Is it a safe box? It is. In the Midwest alone, over 1,000 falcons have been produced at nest boxes that use this design, which provides shelter from the weather and perches for sitting. Netting under the boxes is out of the question, since the falcons would snag their talons, and holes or venting in the side of the boxes to let in wind would also let in rain and snow.

Absent external stimuli, Bob has never seen young falcons jump from a nest box or cliff as they did at Great Spirit Bluff. He believes that insects caused the young falcons to stampede from the box. Just a few weeks ago, 17 of 20 adult whooping cranes in central Wisconsin deserted their eggs due to black flies, as reported in the Wausau Daily Herald. http://www.wausaudailyherald.com/article/20130525/WDH01/305250345/Black-flies-endanger-whooping-crane-nests

Please refer to this blog post for more information about insects, intervention, and fosterage: http://raptorresource.blogspot.com/2013/06/great-spirit-bluff-falcons-intervention.html

Although we knew the gnats and black flies were bad, we were unable to intervene earlier, since that would most likely have caused the young falcons to jump before they had developed their flight feathers. In short, the risk of injury or death was higher if we went to the box than if we did not. This was an unusual and unfortunate situation. We haven't seen it before and we hope never to see it again.

To view the Red Wing Falcons, click on this link, and then choose Red Wing Grain Falcons from the left side and click on that link: http://www.farmyou.com/falcon_cams/index.html. This cam may not always be available, since it has limited bandwidth. 

A big thank you to the Howe family for responding so quickly, climber Dan for last minute assistance, and the staff of Red Wing Grain for letting us foster a falcon into their box on very short notice. Bob made a difficult decision in a stressful situation, but he made it in the best interests of Jonathan, who is thriving in his new home.

Great Spirit Bluff Falcons: Intervention, Insects, and Fosterage

Bugs. Check the video at http://www.ustream.tv/recorded/34496685/highlight/371827

Bob made a decision today to intervene in the situation at Great Spirit Bluff, where four young falcons fell from the front perch. Intervention is always a tough call. He decided to intervene because:

• We have never seen or heard of a situation where three (eventually four) falcons that were 30 days of age or a little younger jumped out of the nest box absent any visible stimuli such as a threat approaching them. Bob said that we might expect to see 'branching' at 35 to 37+ days of age, but 30 days was too young. Something was wrong. His exact quote: "In all of my years of working with peregrine falcons I have never seen young falcons jump or slip off to their death. I have seen falcons nest on 1,000 foot cliffs on a ledge the size of a dinner plate and they always wait until they are feathered enough to fly. I am starting to wonder if we have a unusual hatch of parasites driving the falcons crazy. The only way a young falcon at this age could survive the fall is if by some chance it was slowed down hitting leaves or small limbs. Again, in all of my years of working with peregrine falcons this is new to me. We have had cameras on nesting falcons for twenty years and not witnessed this behavior." 
• We've seen a lot of mortality this year at nest boxes. Of sites that hatched falcons, seven have experienced losses - a record for us. Per the quote, Bob theorized that insects and parasites might be causing problems following an unusually late and wet spring. This gave us a chance to save the falcons, if possible, and determine if parasitism or insects had played a role in driving the young falcons from the box. 

In short, GSBDweller let us know that young  falcons were jumping from the box. Bob decided this unusual behavior needed to be investigated and headed for the bluff. George Howe, director of the Mississippi Valley Conservancy, quickly put together a search team and found another climber to help Bob, since it isn't a good idea for one person to be out on rope alone.

George's team went up the bluff from the bottom, where they found falcon Jonathan. Bob's team waited on top, since the last young falcon was out on the perch. They didn't want to rappel and risk bumping it, since its flight feathers were too short for true flight. If the falcon fell, it might survive if it hit leaves or small branches on the way down. Or it might not. The team elected not to rappel unless the young falcon went back into the box.  However, they were able to observe clouds of insects around the young falcon and adults, once they perched. The falcons were clearly bothered by the insects that swarmed them. 

Bob and Dan had pulled back from the bluff and were packing up when the last young falcon fell. Dan rappelled down to the end of his rope but was unable to find the young falcon. The talus slope is steep and covered in thick brush, and the young falcons would probably hunker down and remain quiet in the presence of human beings and other threats, making them very hard to find. The ground search is over, since at this point we would be more likely to do harm than good. We don't want to drive the young falcons from the top of the talus slope into the brambles, where Travis and Michelle would be unable to reach them. 

So now we needed to decide what to do with Jonathan, the young falcon that was recovered. He was seemingly healthy. Did we want to put him back in the box? Bob decided against it, since he thought it was highly likely he would leap again. We looked at nests with falcons that were the roughly the same age. Red Wing Grain had two falcons only about a day apart in age. We decided to foster Jonathan because: 

• Jonathan was unharmed and should be kept in the wild if at all possible.
• All four falcons abandoned the box due to flies or gnats. Even with treatment, the problem seemed likely to happen again. Since we haven't seen as severe a problem with the falcons at Red Wing, it seemed likely that fostering or augmenting Jonathan would give him the best chance at survival.
• Fostering/augmenting is a proven technique that was commonly used in the early days of falcon recovery. Bob used augmentation a number of times in the early days of falcon recovery. Adult falcons don't count young, so as long as everyone is roughly the same age, augmentation can be used to introduce young falcons into the wild. 

Bob will most likely be fostering/augmenting Jonathan on Wednesday morning (he will keep Jonathan in his mews for a little observation prior to release). It seems likely that our pattern of disappearing and dying young falcons might be caused by insects and parasites in some combination - a "mega-hatch" caused by the late, wet spring. We'll let you know what we find out. 

We have some film clips here: 

• Young falcons and bugs: http://www.ustream.tv/recorded/34496685/highlight/371827
• 1st falcon falls from box: http://www.ustream.tv/recorded/34496685/highlight/371837
• 2nd falcon falls from box: http://www.ustream.tv/recorded/34497469/highlight/371841
• 3rd falcon falls from box: http://www.ustream.tv/recorded/34497469/highlight/371843
• 4th young falcon goes back into box (it fell later): http://youtu.be/SOu32va6oRo

Avian Parasites

On May 22, 2013, the falcon eggs at Xcel Energy's Blackdog nest box began hatching. Immature female 16/U laid four eggs and hatched three. Although both parents diligently cared for their young, they never seemed to thrive. On May 27th, a watcher reporter strange black patches on one of the young. By May 31, two of the three young were dead. We don't know how the first one was disposed of, but the parents fed the second young to the third.

In watching the box, we noticed the strange black patches. We also saw that the remaining baby didn't seem to be developing properly. It was quite small for ten days of age, spent more time under its mother than might be expected, and didn't seem to be developing feathers properly. Perhaps the young falcon had Frounce, a yeast infection of the digestive tract that interferes with food intake. We decided to go up the stack and treat it with Spartrix. This has been a very hard year on our falcons and we really didn't want to lose any more.

I called Dan, our contact at the plant, and made the necessary arrangements. The Blackdog nest isn't especially easy to get to, since it is at the 600' level of the plant's smokestack. An elevator takes you to the 300' level and ladders take you the rest of the way. All told, you need to plan on a minimum of 50 minutes to visit the box. A big thanks to Dan for taking the time out of his day!

I was really shocked when we finally got to the nest. The falcon was very small, coated with black gunk, and swarming with parasites. They were on its back, belly, under wings, and neck. We thought the black gunk might be prey remains, but it was actually scabs, dried blood, and damaged feathers. The parasites,  probably Amblycera or Hippoboscidae, were feeding by chewing soft areas of skin, causing an area of localized bleeding from which they drank.

I decided to give the young falcon Spartrix just in case (Frounce could easily kill a falcon this stressed), and then Dan held the falcon while I carefully cleaned it off.

This is a closeup of the falcon's back and neck. The parasites caused extensive damage, destroying feathers,  interfering with feather growth, and delaying development. I killed and swabbed and crushed and killed and swabbed and crushed again. Once the parasites seemed to be (mostly) dead, I checked the box for anything that might be harboring more, took a few bits out, and returned the baby falcon, along with a dead quail. Mom was back in the box before we were back in the stack, and the quail was gone by the time we reached the bottom. Despite the damage, the young falcon had a good crop and even seemed somewhat feisty, weakly footing with tiny talons. While I don't know that the falcon will survive, we increased its chances of survival.

The parents have been very busy preening the young falcon, sometimes what seemed (to human watchers) rather roughly. We now know that they were trying to remove parasites. But where did the parasites come from? Since lice are transmitted by direct contact, I'm guessing that the lice were brought in on a prey item. According to Science Direct: "With no wings and very small eyes, chewing lice are, by and large, helpless away from their host." However, they were presumably able to hop, skittle, or jump from prey on to the young birds, who lack the armoring feathers of adults and weren't yet preening themselves. We'll be watching this box closely over the next couple of days to see what happens to the young bird.

Ever feel like a tick was crawling on you? Hours later, and I can still feel the lice crawling...

I Found A Baby Bird...Now What?

You've found a baby bird. Does it need help? What should you do? The Ustream Decorah Eagle mods made me aware of a flowchart to help answer your baby bird questions. Since we've been watching fledgling birds in our yard for the past week, I thought I would share it.

This particular flowchart was made by WildCare in San Rafael, California, but you can substitute the name of a local rehabilitation organization if you find a bird that needs care. If you don't know of an organization near you, try searching this website. You can look by location, browse a large list, or filter by animal:

By animal: http://www.wildliferehabber.org/an_disp_list.php
By zipcode and location: http://www.wildliferehabber.org/
By state: http://www.wildliferehabber.org/states.php

Thanks to WildCare for sharing this flowchart! Please pass it on!

http://www.wildcarebayarea.org/site/PageServer

IR Reflective Feathers and Facial Disks

While creating owl highlights this morning for our Eaglecrest site, I came across some very close-up footage of a fledgling owl's face. As the capture above shows, the young owl has a lovely ring of IR reflective feathers around its facial disk. I was curious, so I did a little research. If owls can't see IR light, why would they have IR reflective feathers? Although I wasn't able to find much on IR and feathers, it seems most likely that the ring is produced by melanin, which fluoresces under IR light. Melanin not only produces colors ranging from dark black to reddish brown and pale yellow, it also makes feathers stronger, stiffer, and more resistant to wear.

While many birds have some amount of melanin in their feathers, especially stiff wing primaries, owls instead have porphyrin, a pigment that doesn't stiffen feathers. Soft, serrated feathers aid an owl's silent flight by breaking up turbulence. An angry peregrine falcon whooshes by you, but you won't hear an owl coming (cue creepy music here). Owls are the only birds known to use porphyrin in their wing feathers.

The rigidity of a material also impacts the way it reflects sound. Rigid materials reflect sound better and more quickly than softer ones. To quote: "The speed of sound in a medium is determined by a combination of the medium’s rigidity and its density. The more rigid the medium, the faster the speed of sound." A wall or canyon might produce an echo, but a pillow won't. I tried it myself, just to make sure.

So soft feathers are wonderful for silent flight, but they don't reflect sound nearly as well as rigid feathers. I am speculating that our little barn owl has a ring of stiff, melanin-producing feathers around its facial disk. The stiff feathers channel sound better and more quickly than soft ones would - absolutely crucial for an animal that hunts in little or no light. The contrast between the owl's porphyrin and melanin laden feathers produces a ring effect that might not be noticeable in a bird with more melanin. It is interesting to speculate that 'echoes' produced by the irregularly shaped ring might also aid directional hearing. Changes in the speed of sound might help owls gauge prey distance and location much as bats use echolocation (aside: this might be the most hilarious video about echolocation ever made).

We know that an owl's facial disk is special in many ways, and that barn owls in particular seem to be well-adapted for low to no-light hunting. This looks like another example of owl adaptation in action.

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Thanks to the camera operators at Eaglecrest for the wonderful video! The following things helped me learn about this topic:

• http://thebuffleheadbirder.com/last-owl-in-is-a-winner/
• http://www.birds.cornell.edu/AllAboutBirds/studying/feathers/color
• http://cnx.org/content/m42256/latest/?collection=col11406/latest
• Hilarious video: http://www.youtube.com/watch?v=z7b_E8_fZcc

The Riverside Herons, Xcel Energy, and Rob MacIntyre

The herons return. Thanks to Nora for the cap

Two years ago today, Raptor Resource Project Board President Rob MacIntyre suffered cardiac arrest while assisting his neighbors with cleanup after a tornado in north Minneapolis, MN. He was just 53 years old. The tornado also took the life of Floyd David Whitfield and damaged or destroyed 3,700 properties, including a blue heron colony located in the North Mississippi Regional Park. 

On June 6th of 2011, Xcel Energy staff at the Riverside Plant in northeast Minneapolis informed Dan Orr that blue herons had shown up on a small island owned by the plant. The island, which is sited roughly 50 feet from the east bank of the Mississippi, is believed to be man-made. It may have been built to control water flow or timber floating down the river in the 1890s, when Minneapolis was home to many saw mills. The industry faded in the early part of the 20th century, and the small island quickly became covered with trees. 

The tornado had been devastating, but the re-establishment of the heron rookery provided a lot of hope. We were thrilled with the connection to Rob, his beloved north Minneapolis, and Xcel Energy. Since the Riverside plant already had a falcon cam, adding a heron cam was easy. We also added a kestrel nest box to the plant's reclaimed coalyard, which had been turned into prairie grass. We'll be checking that and the falcon box sometime next week. 

The herons returned in 2013 for a third season on the little island. We hope you enjoy watching them. Fly high, Rob, and know that people still love and care for you. We wish you were here to see the wonderful things that have happened since 2011. 

Rob installing a falcon nestbox at Greysolon Plaza in Duluth