Wednesday, November 19, 2014

Why Are The Eagles Working On The Nest?

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

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

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

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

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

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



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

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



Things that helped me learn about this topic:

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

Friday, October 31, 2014

Eyes in The Night!

In honor of all things spooky, we've been running a feature called 'Eyes In The Night' over on our facebook page. So far, we've seen raccoon, deer, opossum, bobcat, hare, great horned owls, skunk, great crowned night herons, and bullfrogs. We've watched them forage, hunt, eat, and very occasionally interact with one another under IR light, which they can't see. It's fascinating to see just how many animals are busy after dark!

Animals can be classified as nocturnal (primarily active at night), diurnal (primarily active during the day), cathemeral (sporadically active during the day or night), and crepescular (primarily active at dawn and dusk). Whether nocturnal, cathemeral, or crepescular, animals that are active under low-light conditions may have bigger eyes and ears, darker colors, more distinct vocalizations, and quieter movements than their strictly diurnal counterparts.

Seeing
Opossum at Eaglecrest 
Why do the animals and birds we watch after dark have such large glowing eyes? Because their eyes:
  • Tend to be larger and more protruding than those of diurnal or daytime animals. 
  • Often have pupils that open more widely than those of diurnal animals.
  • Often have slit rather than round pupils. Slit pupils are more efficient at opening and closing quickly.
  • Usually have more rods than cones. Rods work better in low light, detecting motion and basic visual information, while cones work better in bright light, registering detail and detecting color. Some nocturnal animals have no cones at all.
  • May have a special light gathering structure called a tapetum, which amplifies the amount of light that reaches the retina. The tapetum reflects light that has already passed through the retina back through the retina a second time, giving it another chance to strike the light-sensitive rods. The animals we watch can't see IR light, but their widely dilated eyes certainly reflect it!

Hearing
Deer are crepuscular, or active at dawn and dusk.
Their large, moveable pinna give them excellent
directional hearing. 
Why do the animals we watch after dark spend so much time listening? Many nocturnal animals rely on their hearing as much or more than their vision. How are their ears different from those of diurnal animals? They might have:
  • Enlarged pinnae (the outer part of the ear), facial disks, or other features that help them gather and condense sound.
  • Directional location. Think of ears as a microphone. In some animals (bobcats, for example), pinnae can be moved to funnel sound into the inner ear, helping localize the source of sound. Other animals, like owls, have offset ears that provide a precise x/y prey point based on a sound’s location.
  • Inner ear structures that maximize high frequency sounds (like mice rustling in the leaves). This might include denser, shorter auditory hairs, and denser auditory nerves. All the better to hear you with, my dear! 
  • Ultrasonic hearing. Bats are famous for echolocation, but some moths and nocturnal butterflies have ultrasound-sensitive ears on their wings to help them escape. 

Smelling 
Opossum flehvening at Eaglecrest
Why do the animals we watch spend so much time smelling things? In a low to no-light world, scent conveys important information about potential mates, rivals, predators, and dinner. Nocturnal animals:
  • Often have a larger olfactory epithelium, which improves their sense of smell. The sense of smell is most highly developed in nocturnal mammals, although some nocturnal birds also have a sense of smell. An improved sense of smell helps nocturnal animals find food and avoid becoming dinner under low-light to no-light conditions.
  • Often communicate via scent marking and smell. Scents intimidate rivals, attract mates, convey information about health, and provide information about numbers and types of animals in any given place. 

Touching
Nocturnal animals are very sensitive to touch. Many of them have special adaptations to help maximize touch in low-light or no-light situations, including:
  • Vibrissae, or whiskers that serve as tactile organs. While many animals have vibrissae, they tend to be more prominent on nocturnal animals or animals that hunt in low light. Vibrissae may be found on an animal’s face, forelegs, or feet. 
  • Sensory maps that maximize the input from vibrissae, antennae, and other tactile sensors. A study by biologist Dennis O’Leary found that a mouse’s sensory map is dominated by clusters of neurons that process whisker signals. A cluster for one whisker is bigger that the cluster of neurons dedicated to the mouse’s entire foot. 
  • A higher percentage of the cerebral cortex dedicated to touch. For example, almost two-thirds of the area responsible for sensory perception in a raccoon's brain is specialized to interpret touch. 
In a dark world, special adaptations help animals find food and mates, avoid predators, and defend their territories. I am grateful to have a chance to see them, spooky or not! Every time I step outdoors after dark now, I think about all of the animals that might be active around me.

Did you know...
While we don’t understand all of the ways touch works, image maps called cortical homunculi help map tactility. Check it out:
Links that helped me understand this:


Wednesday, October 15, 2014

When will Mom and Dad...

When will Mom and Dad work on the nest? When will Mom and Dad mate? Are the eagles in Florida going to lay eggs early? "What's going on?!" everyone seems to be wondering.

Mom and Dad are on Eagle Time, which makes their behavior a little harder to pin down by our own clock! Still, their past behavior provides some clues. We should see work on the nest beginning in October and accelerating through the end of the year. In January, the eagles should move deeper into courtship. In addition to nest-building, we should see pair perching, vocalizations, bill stroking and pecking, and some footing or body stroking. Towards mid-to-late January, the eagles should begin bringing soft nesting material such as grasses, corn husks, and corn stalks in to line the nest bowl. Dad will begin sharing food (sometimes reluctantly), and physical contact will accelerate with even more touching, footing, and beak kissing. Mating will most likely begin in late January or early February, followed by egg-laying in late February or early March,

The US Fish and Wildlife Service's Bald Eagle Management Plan has a chronology for nesting activities in various parts of the United States.

Northern US. Includes Decorah, Fort St. Vrain, MN Bound

Southeastern US. Includes Florida Eagle cams, Berry College

As the chart clearly shows, the bald eagles in the Southeastern US are running on SEET (Southeastern Eagle Time) when compared to bald eagles in the northern US. However, eagles in both regions are right on time for their behaviors. In Iowa, Colorado, and along the Mississippi river in Eagle Valley, eagles are beginning to visit and work on nests.
If you can't keep up with the nests live, you are welcome to visit our Facebook page and/or forum.

The US Fish and Wildlife Service website contains some very good information on BE nationwide. Go to http://www.fws.gov/midwest/eagle/conservation/baea_nhstry_snstvty.html for a live web site or http://www.fws.gov/midwest/eagle/pdf/NationalBaldEagleManagementGuidelines.pdf for a .pdf of the management guidelines.

Monday, September 29, 2014

Four and Dispersal

Four back in Decorah. Photo credit Bob Anderson.
Last week, Four took a little trip 22 miles northwest of her natal nest, although she has since returned and reconnected with Mom and Dad. What was Four doing? Will she ever permanently leave Decorah? How do we define and classify the behavior of a highly nomadic species like the bald eagle? I can't tell you what Four is thinking, but I can tell you a little bit about eagles and their movements.

Dispersal is the movement of individuals from their point of origin (natal area) to where they reproduce or would have reproduced had they survived and mated. Navigation is an animal's movement around its territory or home range. Migration is the regular, seasonal movement of animals between breeding and non-breeding areas. While D1 hadn't yet bred, she was clearly migrating back and forth between a non-breeding territory (Polar Bear Park) and a territory in which she would be likely to breed (NE Iowa).

It is theorized that animals disperse for one of three reasons:
  • To avoid inbreeding
  • To avoid kin competition
  • To colonize new habitat
A detailed discussion of these theories can be found here, but all three dispersal strategies are linked to reproductive success. Inbreeding takes a toll on reproductive fitness in the long run, and kin competition can have immediate deleterious consequences, especially if kin are competing over limited resources. Colonizing new habitat disperses a population across a wider area, so local extinctions have a lower chance to kill every individual in a population.

Having said that, D1, D14, and Four didn't sit down and check off a list of reasons prior to dispersing. Dispersal seems to be triggered by a number of factors, including hormones, body condition, reduction of parental provisioning, increased locomoter activity, and external factors that include favorable winds and full moons for night flyers. In short, our eagles learned to fly and hunt, Mom and Dad decreased feeding, an adrenally-produced hormone called corticosterone soared, and the eagles dispersed. Reports of Four and the other eagles playing 'tag' with Mom and Dad shortly before dispersal may really have been a hungry, hormonally-charged young eagle chasing down its parents in an attempt to secure food from them. Suddenly tag seems a little less playful.

Unlike dispersal, migrating animals usually move from one geographic region to another without using intervening habitat.  But are dispersal and migratory behaviors mutually exclusive in an highly nomadic animal that usually doesn't breed until it is four years of age or older? What limited data we have indicates they aren't. D1's first year had characteristics of both dispersal and migration. She left her natal territory on August 13, 2011 and flew 262 miles northwest, arriving at her northernmost destination on September 6th. She spent the next four months slowly traveling south, with long layovers at Yellow Lake and Black River Falls. She arrived back in NE Iowa on December 24th, 2011.
D1 in 2011
D1 spent her winters navigating throughout NE Iowa and SE Minnesota, but she refined her north/south movements considerably. By 2014, her 808-mile trip north to Polar Bear Park took just 16 days. Although she wasn't yet breeding, her trips fulfilled the criteria for migration: they were seasonal, endogenously controlled, and didn't use much intervening habitat.

RRP board member Brett Mandernack is researching the migratory behavior of immature bald eagles. If there is a difference in immature vs. adult eagle migration, when does this change occur? Is it gradual over the first several years of the eagle’s life or is the change abrupt? D1, D14, and Four are part of his work. The paper from his first study, which examines data collected between 1999 and 2006, was published in the Journal of Raptor Research in 2012. An abstract can be found at http://dx.doi.org/10.3356/JRR-10-77.1

So will our eagles choose to nest in Decorah as adults? It's not impossible, but it isn't likely either. Dispersed young may return to the vicinity of the nest, but they don't appear to spend time there as sub-adults or adults. A study of 878 bald eagles found a median natal dispersal distance of 42 miles (69.2 km) overall, with females dispersing farther than males. Unlike human families, the young do not return for a visit with grandchildren in tow.

Eagle cluster map. Decorah is marked by the red 375, but note other favorite spots
Does an eagle's initial dispersal or overwintering perambuation tell us where it might nest as an adult? D1's favorite wintering area was near Elkader, Iowa, about 35 miles south of her natal nest - in line with average disperal distances. Unfortunately, her transmitter stopped talking to us. We'll try to get a visual on her this winter but we can't guarantee it.

As I mentioned at the beginning of this post, Four is back in Decorah and reunited with at least one parent, although we haven't seen them feeding her. We'll let everyone know if she leaves again.



Things that helped me learn about this topic:

Thursday, September 18, 2014

Flight Maps

Will Four ever disperse? We've been asked that question via facebook, email, and our forum. Only Four can answer that question, but I thought it might be worth looking back at D1 and D14 for clues.

D1's first flights, 8/01/11 to 8/12/11
The map above shows D1's first flights. She fledged in June, at 81 days of age, and we attached the transmitter to her on July 18, 2011. The maps shows her exploring her natal territory, traveling simple, short back and forth paths as she learns proficient flying, food-finding, and navigational skills.

D14's first flights, 8/01/12 to 8/12/12
D14 was 78 days old when he fledged in late June, He is less centered around the nest and hatchery than D1 was, but his initial exploratory flights are very similar. Like D1, he is flying short, simple back and forth paths as he gains skill and experience. 

Four's first flights, 8/01/14 to 8/12/14
Four's fledge occurred at approximately 76 days old, in late June. Like D1 and D14, her early flight pattern is relatively simple  - a lot of short back and forth explorations. Her first "loop" occurred on August 10 and was just 1 mile long (.5 miles out and back). 

So when does a hatch year eagle stop exploring and start dispersing? D1 was quite obvious. On August 13 2011, she flew north 14 miles toward the Iowa/Minnesota border. By September 6, she was 262 miles north of the nest. She turned south and came back to Decorah, arriving back in NE Iowa on December 24, 2011. Before leaving on August 13, she had never been recorded more than .98 miles from her natal nest.

D1's 2011 dispersal
The map above displays D1's entire dispersal. On August 13, she went from local travel along simple paths to long-distance travel along more complex paths. Her large loop included several smaller loops with fewer of the simple back and forth flights that we saw her first weeks on the wing.

D14's 2012 dispersal
Unlike D1, D14 spent more time flying around the Decorah area and left town twice: once on September 5, for a 24-mile flight south, and once on September 22, for good. So did he disperse on September 5 or September 22? My money is on September 22. D14's movements seem to indicate a higher degree of pre-dispersal restlessness, but he didn't leave permanently until September 22. Like D1, he went from local travel along simple paths to long distance travel that included looping flight. Unfortunately, he died of electrocution on November 6 near Rockford, Iowa. The loss of D14 was tragic for personal and research reasons. Everything we could have learned from him ended in his premature death.

As their flight paths show, D1 and D14 spent some time acquiring skills and strength before dispersing. They needed to be able to fly strongly, work with the wind, find food, and navigate. We have recently begun seeing some increased complexity and distance in Four's flights. Only time will tell if and when she disperses, but Four's flight paths and recent calf-eating excursion seem like good signs. Stay tuned! You can make your own D1, D14, and Four maps here: http://www.raptorresource.org/maps/personal.php

Four, 9/1/14 to 9/17/14

On Migration

At whatever moment you read these words, day or night, there are birds aloft in the skies of the Western Hemisphere, migrating. If it is spring or fall, the great pivot points of the year, then the continents are swarming with billions of traveling birds...
- Living on the Wind: Across the Hemisphere with Migratory Birds

We get a lot of questions about migration. Do the Decorah eagles migrate? Do our Peregrine falcons migrate? Where do they go when they leave? We fitted our eagles with tracking devices in part to help answer some of these questions. To date, we've learned D1's migratory paths and summer and winter ranges, observed an interesting difference in dispersal patterns between D1 and D14, and an interesting similarity between D14 and Four. 

I used to think migration was very simple. Like a lot of people, I thought that all birds except chickadees, pigeons, crows, and woodpeckers migrated once it got cold. They went south to escape snow and ice, returning to nest when the weather warmed up. 'South' was anywhere it didn't snow, or at least didn't snow much: Georgia, the Gulf Coast, South America. I had no idea that many birds don't migrate, or that 'south' could be Minnesota or Wisconsin. Peregrines, Snowy Owls, and Bald eagles taught me otherwise.

Among birds, migration is the regular, endogenously controlled, seasonal movement of birds between breeding and non-breeding areas (Salewski and Bruderer 2007). Bald eagles and Peregrine falcons are partial migrators - that is, some members of the species migrate and others don't. This is the most common type of migration, which makes sense since migration is driven by a number of factors, including daylight length, food availability, weather, the time it takes to raise young, and the distance between wintering and breeding grounds. Migration allows exploitation of different habitats as environments change seasonally or successionally (Dingle, 1996). Food availability seems to play a very important role in the migration of Bald eagles: inland northern Bald eagles tend to move southward after ice and snow start putting a lid over their favorite food source - fish, while southern Bald eagles are thought to move northward once warm weather drives fish into deeper water (although there is some debate about this). Weather can also impact migration timing in other ways: for example, a favorable wind pattern might help compel a bird to leave for its wintering or summering grounds if other factors are in place.

D1's looping migratory path in 2012 and 2013
I also thought that birds used to travel the same path backwards and forwards. However, it turns out that many birds, including our own D1, favor loop migrations. This pattern might be a response to seasonal prevailing winds, food availability, tradition, and/or genetic influence. More to the point, loop migrations require more complex navigational skills (and perhaps inheritances) than a simple point A to point B path.

So how do birds navigate? Migration studies have found five major methods: 
  • Magnetic sensing: Some birds, including pigeons, are able to use the direction and strength of Earth's magnetic fields to orient themselves. http://www.nytimes.com/2012/04/27/science/study-sheds-light-on-how-pigeons-navigate-by-magnetic-field.html?_r=0
  • Geographic mapping: When I'm in Minneapolis, I use a number of tall buildings to help me orient the city. It turns out that birds do the same thing, using landforms and geographic features such as rivers, coastlines, and mountain ranges to guide them.
  • Celestial navigation: migratory birds use the position of the sun (during the day) or the rotation of stars (at night) to orient themselves. Experiments done by Dr. Emlen in 1967 indicate that celestial navigation is learned. http://www.birds.cornell.edu/AllAboutBirds/studying/migration/navigation
  • Wind patterns: A recent study at Cornell using crowdsourced data found that passerine birds are heavily dependent on wind direction for migration. By shifting routes, birds take advantage of stronger tailwinds in spring and less severe headwinds in fall.
  • Learned Routes: Some bird species, such as sandhill cranes and snow geese, learn migration routes from their parents and other adult birds in the flock. Once learned, younger birds can travel the route successfully themselves.
What do Bald eagles and Peregrines do? It seems they most likely use multiple sources of information, including celestial and magnetic clues, light polarization, wind patterns and direction, and geographic cues (which would likely be highly correlated with geography). Although parents and young don't migrate together, D1 and D14 were in the company of other eagles every time we saw them, so I suspect that some degree of learning, or at least following, also plays a role. While we haven't yet seen Four in the company of eagles outside her family, she's only begun her wandering. Since young bald eagles are much more nomadic than adult Bald eagles, we hope to have several more years of watching her. 

In addition to watching our eagles, keep an eye on the animals outside your window. We know fall is here, and so do they.
  • Birds may begin gathering in huge premigratory flocks, gorging on food to build fat reserves, and exhibiting restlessness, also known by the marvelous word zugunruheThese behaviors help prepare birds for migration. Keeping a well-stocked bird feeder helps them too.
  • Juvenile peregrine falcons are on the move! You'll sometimes catch a stranger on cam as they disperse down river. Please let us know if you get any band numbers! 
  • Frogs and turtles may begin migrating from summering breeding grounds to deeper bodies of water. While their travels are short, they still fit the definition of migration. For more on frog hibernation, click here. The Minnesota DNR has a very good article on helping migrating turtles cross roads, some cities close roads, and volunteers help keep migrating frogs safe. 
  • Some insects migrate and others hibernate. Aggregating paper wasps may be getting ready to hibernate, while dragonflies migrate in large numbers (or check this source out).
  • Watch out for migrating Mule deer! According to National Geographic, they make a 150-mile migration twice yearly from the low desert to the high mountains.
Have a happy fall and take the time to watch for migrating birds and other animals! Would you like to know if the winds are favorable for bird migration in your area? Check these links out: 


Some things that helped me write this post: 
* Regarding male Peregrine dispersal: of course, there are exceptions. We released Zeus, the male at Woodman Tower in Nebraska, in Rochester New York. We were very surprised when he showed up in Nebraska. Did he fly west intentionally or was he some how blown off course or lost? 

Friday, August 08, 2014

Banding Report: Minnesota Power

From our friends at Minnesota Power. Thanks for sharing!

Amy and Matt
The three chicks at Hibbard Renewable Energy Center now have names as well as leg bands.

The youngsters, two females and a male, are Spike, Jolt and Surge. The Hibbard falcon names were dreamed up by Jodi Piekarski, supervisor, generation production at Boswell. She submitted the names Spike, Jolt and Surge, and employees selected the three as winners in a Powergram online contest that attracted a total of 170 electronic votes.

The votes were tallied today, the same day that Bob Anderson and Amy Ries of the Raptor Resource Project were in town to band the chicks born about four weeks ago. Earlier in the day, they also banded the chick born at Greysolon Plaza in downtown Duluth.

Ries, along with Minnesota Power employees Doug Braff and Matt Pohl, climbed the stack at Hibbard as the youngsters’ parents circled and screeched in alarm and news crews from WDIO, KBJR and Fox television stations watched from the roof and documented the climbers’ progress. The nesting box is on a platform on the stack about 200 feet above the ground.

Doug Braff and friend
It was a climb that only a short while earlier was in jeopardy. The MP safety crew—John Hollingsworth, Ian Wenzel and Dan Belluzzo—were checking weather conditions and monitoring lightning strikes. Fortunately, a storm that had been moving closer to Hibbard dissipated and banders were given the go-ahead.

It was Pohl’s first time as part of the banding team. He said he volunteered to help because “I figured it was a unique opportunity.” He said he rarely has climbed anything higher than the roof of his home and Tuesday’s climb “wasn’t as scary as I was expecting.”

Braff, who supports Minnesota Power’s Falcon Cams and is a veteran falcon bander, described the chicks as “feisty,” the conditions as “nice and breezy” and said the experience was “wonderful, as usual.”

Ries checked the chicks for any signs of disease or parasites and placed the bands around their legs. The bands help researchers study the movement and habits of the birds. “They look great,” Ries said as she removed her climbing and safety gear after the climb. “They’re just really nice looking falcons.”

One egg at Hibbard and the four eggs at Boswell Energy Center failed to hatch this spring, and Anderson attributes that to cold temperatures at a critical time. It was a theme the Raptor Resource Project, based in Decorah, Iowa, has seen play out at many falcon nests in the Midwest this year.

Still, even with no luck this year, Boswell is one of the most productive of the Midwest power plant sites, he said. More than 60 peregrine chicks have hatched at Boswell since 1993 and 15 chicks have been banded at Hibbard since 2008.

Contest details

Piekarski’s names received 73 of the votes cast by employees, or 42.9 percent of the ballots. Finishing second in the voting was the trio of Louie, Copper and Ace. The names Aspen, Spruce and Birch finished third in the voting. Breezzy, Chillee and Bhurrrrr captured fourth place (and last in spelling).

In her naming submission, Piekarski said her electricity-based falcon names were tied to the speed of the peregrine falcon: Spike being “a sudden increase in the amount of electricity that a system produces;” Jolt signifying “a sudden strong increase in energy;” and Surge “a sudden increase in electrical power that can damage equipment connected to it.”

For her winning entry, Powergram will present Piekarski with a beautiful 8-by-10-inch peregrine falcon print.

Wednesday, July 09, 2014

EWOT's Electrocution

Yesterday at about 10:45, Decorah fledgling EWOT was electrocuted on a high voltage power line roughly ½ mile from the mulch pile that both fledglings have been spending most of their time on. It was reported to us late in the afternoon. We collected and examined him, returning to the site of the electrocution to gather more information once that was done. Here is what we know.

The line was a 96 Kilovolt transmission line owned by ITC Holdings (http://www.itc-holdings.com/). In general, electrical delivery can be divided into two types: transmission and distribution. High-voltage transmission lines carry electricity over long distances from power plants or grids to substations. The poles or towers are physically larger and taller than those that support lower-voltage distribution lines and don’t support anything except electrical lines. Distribution lines carry electricity from substations to consumers and are supported by what most of us probably think of as utility or power poles. Utility poles are often made of wood and, unlike transmission lines, may also carry telephone and cable wires or support street lights.

ITC is able to detect fluctuations and other anomalies on their lines. When they sensed an anomaly, they sent a field technician out to investigate. He found and collected EWOT, and turned him over to the Iowa Department of Natural Resources. They saw the transmitter and called Bob to let him know that an eaglet had been electrocuted.

When we first got word of another electrocuted eaglet, we assumed it had contacted a standard utility pole. According to Refining Estimates of Bird Collision and Electrocution Mortality at Power Lines in the United States, electrocutions occur primarily at distribution lines, while collisions occur at both distribution and transmission lines. That’s certainly been our experience, since every eagle we’ve picked up has been found at the base of a distribution line. I pictured a standard wooden utility pole as we glumly drove over for our field investigation. I was surprised to instead find a high-power line between a field and a hill. We hiked out and took a look at the scene. We weren’t able to find scorch or singe marks on the pole or insulators, and the eaglet’s body was not at the base of the pole, as we’ve seen elsewhere, but under the lines three to four feet from the pole.

An examination of the eaglet’s body revealed singeing and burning around his elbow and feet. Electrocution can’t happen unless a bird’s body creates a circuit between ground and voltage, or different voltage phases, allowing energy to flow from high to low. Sitting on a wire won’t harm a bird, since it doesn’t create a circuit. But he closed a circuit with his wing and one foot, creating the flow that killed him.

In addition to singeing, the eaglet’s wing had extensive tissue damage and some severing. Although it seemed unlikely, we needed to know whether the transmitter had somehow created or closed the circuit that led to his electrocution. A quick look at the transmitter showed no damage, scorching, or discoloring. We cut the straps and removed it from EWOT’s body. The straps were intact and there was no scorching, singeing, or burning under the straps or backpack pad. Finally, we made sure the receiver could detect the transmitter. The transmitter was functioning normally, so we concluded it hadn’t been part of our eaglet’s electrocution.

Bob contacted ITC this morning. The biologist he spoke with told him that they hadn’t seen an electrocution on a high kilovolt line in the three years he’d worked for ITC. Having said that, they reported the electrocution to the U.S. Fish and Wildlife Service and the Avian Power Line Interaction Committee, and they are assessing steps that can be taken to prevent another electrocution or collision.

What we think
The pole was up to code and we haven’t had any problems at a transmission line before, so we suspect the electrocution was a terrible accident. Other electrocutions and near-misses in Decorah involved distribution poles with wonderful perching spots near the hatchery, where the eagles regularly hunt, fly, and hang out.  The transmission pole provides a bad perching spot overlooking a poor hunting ground bordered by trees. Although electrocution was clearly the cause of death, we suspect that EWOT might have collided with a wire and dropped, contacting other wires or the pole before dropping to the ground. Death was very quick.

Where do we go from here?
We don’t know whether ITC will install diverters or a similar non-collision technology over one death. Companies tend to set priorities based in large part on collisions, electrocutions, and known migration/movement paths. Reporting is key and we are very glad the company didn’t choose to sweep the electrocution under the rug.  
Bob talked to ITC this morning. If there are any more deaths, the company will report them to us, the DNR, and the USFWS.  Neither D1, D14, or Four have spent any time near the high voltage line, but if Four or D1 start hanging out, we’ll make ITC and everyone else aware of it.

Why can’t you build safe perches?
Alliant Energy, the D12 Memorial Group, the Decorah High School, and Decorah Building supply were able to make the distribution poles at the hatchery safer through insulation and safe perches. However, we’re not sure this was a perching problem and we can’t encourage perching on high voltage transmission lines since they are too dangerous. If protection is installed, it will probably be in the form of diverters that make it easy for birds, including eagles, to see the power lines.

What can we do?
Our wonderful fans want to know what they can do to make power lines safe. A few suggestions:
  • ·      Does your power company have an Avian Protection Plan? Click here for more information: http://www.aplic.org/APPs.php. Birds aren’t the only issue, either – my electrical cooperative is upgrading equipment because of squirrels! Talk to your company and find out what they have in place.
  • ·       Report electrocuted animals to your power company and wildlife agency. If your power company shrugs it off, document the problem and talk to your state’s regulatory agency. It’s my experience that most utility companies are very responsive to electrocutions. They kill animals, destroy equipment, can start fires, and are expensive.
  • ·      Learn more about the issue. A few good places to start:

While we can’t protect transmission lines with safe perches, most of our electrocutions have been on distribution lines. This seems like a good time to share the story of the D12 Memorial Group’s work with making distribution poles safer. 
We are really dismayed by the electrocution of another eagle but believe we can do better in the future. We’ll continue working with power companies to improve outcomes for birds of prey and we’ll certainly let you know what happens here. In the meantime, please feel free to share your stories of improvement and recovery with us.