Tuesday, December 11, 2012

2012 Annual Report

Our annual report is now available online. The report discusses 2012, talks about 2013, and contains plenty of information and observations from the sites we monitor and band at. Enjoy! 


Thursday, November 29, 2012

11/27/12: D14 Announcement

We are sorry to announce that Bob Anderson found D14 dead yesterday near Rockford, Iowa. D14, a 2012 hatch year bald eagle from Decorah, Iowa, was electrocuted after landing or trying to land on a power pole. Bob immediately notified the utility company. D14's body will be sent to the National Eagle Repository, where his feathers and other parts will be distributed for use in Native American religious ceremonies. Bob and Brett Mandernack did a close exam
ination of D14's body. He was healthy and butterball fat. There were no signs of wear from the transmitter or backpack.

How common is electrocution? A federal study done in the 1990s identified impact injuries, poisoning, gunshot, and electrocution as the top four sources of bald eagle mortality. We haven't seen it in Decorah until this year, but D14's transmitter was the only reason we were able to follow him after he left the nest. New poles commonly have bird safety devices since bird electrocutions are not only tragic, but can cause fires and power supply disruptions. However, many old poles remain and safety devices don't always work. It's been known since the 1920s that power lines and poles can present a danger to birds. As Bald eagle (and presumably other large bird) populations expand, more electrocutions may happen.

D12, a sibling of D14, was electrocuted earlier this year. A group calling themselves The Memorial for D12 Facebook Group (aka The Raptor Nation) responded by working with Alliant Energy, Puget Sound Energy, Decorah High School, and Decorah Building Supply to develop and fit bird-safe perches for the hatchery. I have a blog post and links about that here:http://raptorresource.blogspot.com/2012/11/bird-safe-power-poles.html.

If you'd like to initiate a perch project in your area, please talk with your local power company. The following links provide wonderful sources of information:

Avian Power Line Interaction Committee: http://www.aplic.org/
D12 Memorial Group story: http://raptorresource.blogspot.com/2012/11/bird-safe-power-poles.html
Avian Protection Devices: http://www.srpnet.com/environment/aviandiagram.aspx
D12 Perches: http://www.flickr.com/photos/68092929@N03/8203641600/

All raptors - all wild animals - face myriad dangers in their lives. It is easy to forget that watching and tracking them doesn't protect them. We'll miss following D14.

Monday, November 26, 2012

Bird Safe Power Poles

Adult Eagles on Perch
This post is about a group inspired by the electrocution of eaglet D12 in the summer of 2012. The Memorial for D12 Facebook Group/The Raptor Nation worked with Alliant Energy, Puget Sound Energy, Decorah
 High School, and Decorah Building Supply to make and install safe perches at the hatchery. In their own words: 

"After the death of Decorah Eaglet D12 by electrocution, D12 Memorial Facebook Group/The Raptor Nation member Ruth Mitchell came up with an idea. Her vision was to build perches to make the electric poles in the hatchery area safer for the Decorah Eagles. Becky Burland agreed to explore the possibility and do the footwork in Decorah.

From the beginning, Alliant Energy's Shawna Sailor was very interested in the project. She realized the magnitude of the loss of D12 as the first known tragedy at the DE nest. Shawna and Alliant engineer Dennis Dye worked diligently to learn about perches and Alliant's ability to use them along with their existing equipment.

Mel Walters of Puget Sound Energy was instrumental in educating us about perches and how Alliant might design a perch to meet their specifications. Puget Sound Energy is a leader in the industry in making electricity safer for raptors and other wildlife. Mel explained that they have 1000 eagle nests in their area and they are always working to increase safety for the area raptors. Along with perches, they also use bird guards and perching deterrent strategies. We were lucky to have Mel share his experience and knowledge with us.

Part of Ruth Mitchell's vision was to have local students build the perches. It was hard to imagine Alliant allowing students to be a part of this specialized collaboration, but Becky talked with John Condon, the Industrial Tech teacher at Decorah High School. He was excited to participate in a project that would help teach students the basics of reading a blueprint and executing its construction. John was also confident that the students could meet Alliant's quality assurance expectations. A previous class made the eagle bike rack that was installed at the hatchery in 2012.

Representatives of Alliant Energy, Decorah High School and The Raptor Nation met recently to finalize the Perch Project. Alliant Energy is donating all the hardware and installation labor, Decorah High School students are donating the labor of building twenty perches, and Decorah Building Supply donated 50% of the lumber needed for the perches.

John Condon of Decorah High School reports the class will start building the perches sometime between Thanksgiving and Christmas. Alliant will install seven perches on the hatchery poles that Bob Anderson of the Raptor Resource Project identified as most important for protection. They will use the other thirteen perches as popular bird poles are identified."

The Raptor Resource Project thanks The Raptor Nation/D12 Memorial Facebook Group, Alliant Energy, Puget Sound Energy, Decorah High School, and Decorah Building Supply for their hard work on behalf of the Decorah Eagles. We'll keep you posted on the installation. Follow the link below for a look at the perch blueprint.


Friday, October 26, 2012

The Decorah Eagles Have Surprised Us With A New Nest!

Mom and Dad are surprising us again.  We have noticed in recent weeks that they seem to be building an alternate nest in the neighborhood.  This is not unusual for bald eagles, but it is new for Decorah.

The two bald eagle nests in the photograph above are located roughly 500 feet away from one of Minnesota's busiest interstate highways. The nest at the left was the first nest built by the resident bald eagles, who raised at least eight clutches before deciding to build a new nest in the same tree. I watched them raise young in the lower nest last year, observing in fits and starts as I drove by or sat immobilized in traffic. But I wasn't able to watch them build their new alternate nest, located above and to the right of the original nest, so I'm not sure exactly when they started.  I've seen eagles sitting in and perching by the alternate nest this fall, and I'm pretty sure the female will lay eggs in it come late winter.

Bald eagles build the largest nests of any North  American bird (Stalmaster 1987). So why would they invest the time and energy to build a new nest when the old one remains perfectly serviceable as far as we can tell?  Several hypotheses have been proposed to explain it:
  • Alternate nests may serve as 'insurance'. If the occupied nest is destroyed or rendered unusable, the eagles can quickly occupy the alternate without having to build a new nest.
  • Changing nests from year to year helps the eagles avoid parasites and 'nest mates' who are attracted by the food the eagles bring in. Shifting nests from year to year may help the eagles avoid parasitism.
  • The additional nests may be a way of marking territory. They warn other breeding pairs away and demonstrate fitness on the part of resident adults.
  • Eagles like to build nests.
Although we haven't seen it in Decorah before, multiple nest building is a relatively common activity: in most but not all instances bald eagles will have more than one nest in their breeding territory. In one study of 924 territories, eagles were found to have an average of 1.5 nests in their breeding area. In another study of 318 territories, 45% of eagles had two nests or more (Stalmaster, 1987). Eagle nests can be classified as active (shows or showed evidence of breeding by bald eagles during the current or most recent nesting season), alternate (intact or partially intact and used by bald eagles at any time during the past five nesting seasons, but was not used during the current or most recent nesting season), or abandoned (inactive through six or more consecutive nesting seasons). It takes six years for a nest to go from 'alternate' to 'abandoned', since last year's alternate nest might become this year's occupied nest. Why? Only the eagles know for sure.
It is interesting to us that, like the bald eagles in Lino Lakes, the Decorah eagles occupied a single nest for several years before beginning an  alternate. The new nest in their territory is located nearer the trout hatchery, roughly 300-500 feet from their current nest near the woodshed. We don't know at this point which nest they will occupy next spring. Bob did find a dead buck beneath the foot of the 'alternate' tree, which could have played a role in their decision to choose this particular location. But we don't know that for sure.
Here's a peek at the alternate nest (photo by Jim Womeldorf):

To recap:
  • Bald eagles commonly build multiple nests on their nesting territory.
  • Mom and Dad have started construction of an alternate nest about 300-500 feet from their current location.
  • We will not do anything that might influence them to abandon construction of this nest, including camera installation or nest invasion. We cannot and will not disturb them: building multiple nests is part of eagle life. The health and welfare of the eagle family is more important than the nest they choose or our desire to watch them on camera. We'll miss following them, but it is exciting to see them building a new nest! Once again, Mom and Dad are giving us new insights into the lives of bald eagles.

If the eagles do adopt the new nest:
  • We will provide photographs and updates from the ground.
  • We will consider putting a camera in it next year, in early fall.
A few things to ponder: 
  • Is the length of time a mature pair stays on territory correlated with the construction of alternate nests? Five or six years would be plenty of time for parasites and 'nest mates' to become problematic, or at least annoying.
  • Is the length of the bond between the pair a factor? More experienced (older) Bald eagles seem to be better at parenting in many ways. Would a more experienced pair be more likely to build an alternate nest for insurance?
  • Does the actual or perceived encroachment of other adult eagles play a role? If other eagles are present, resident eagles might feel a little more compelled to mark territory.
We would really like Mom and Dad to use the nest they have occupied for so long, but we cannot and will not interfere if they decide to use the new nest. As we said in an earlier post on intervention, their lives are a gift we have been privileged to share. We can only hope we'll get another chance in 2013.
Stay tuned and we'll keep everyone updated as the situation develops!

Things that helped me write and learn about this:
  • Book: The Bald Eagle. Mark Stalmaster, 1987. This is a wonderful book, and the eagle illustrations are charming.
  • Book: The Bald Eagle: Gerrard and Bortolotti. Another great book.
  • Green Value Nursery, Hugo, MN. Thanks for letting me park and walk across your land to get photos of the Lino nest. I'll buy flowers from you next spring!
Note: I got an email from Nancie Klebba in Lino Lakes. She says:

I spoke with a few people on the board that live on the lake and the City's environmental coordinator and they believe the nest has been on Peltier since about 1993 or 1994.

Marty the environmental coordinator said he would check back to see if he could find the exact date.  He  also said the old nest has not been used the last few years.

Thanks, Nancy!

Tuesday, October 16, 2012


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 two young eagles with tracking devices in part to help answer some of these questions.

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 and Bald eagles taught me otherwise.

Bald eagles and Peregrine falcons are partial migrators - that is, some members of the species migrate and others do not. Mom and Dad Decorah both stay put on their territory year round. They have abundant food and water, so there is no reason to leave. Belinda, the falcon at the Xcel Allen S. King plant in Stillwater, Minnesota, also has a history of staying put. There is abundant food on territory and an open water supply slightly south of the plant. In both cases, the resident bird or birds' presence may make it easier for them to preserve their territory without having to chase off interlopers that set up house in their absence.

However, other birds, even those with defined nesting territories, leave. Immature and adult Bald eagles congregate in large numbers by open water along the Mississippi river, a very important flyway for many kinds of birds here in the midwest. Belinda may stay put but it is not uncommon to see interloping falcons at empty nestboxes: just two weeks ago, Brenda Geisler spotted a Peregrine falcon from North Dakota at the Great River Energy nestbox in Elk River, Minnesota. What is migration and why do some birds stay put while others leave?

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 (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.

In general, young Bald eagles are much more nomadic than adult Bald eagles, something we've seen with both D1 and D14. In spring and summer, hatch-year and young sub-adult eagles may fly north to over-summering areas in the northern United States and southern Canada, returning to their birthplace in late summer or early autumn. Or they may not, as we've seen with D14. We don't know why D1 dispersed so much farther than D14 in her first year. Among Peregrine falcons, females tend to disperse farther than males* , but I haven't been able to find documentation of gender-related dispersal in Bald eagles. I'll keep looking, and you are welcome to post links and resources in the comments. Perhaps further study will shed some light on the issue. Eagle migration and dispersal is very complex.

So how do birds navigate? Migration studies have found four 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
  • 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. Again, we really have no idea why D1 and D14 behaved so differently.

We suspect that D1 will come back to NE Iowa this winter, following Lake Superior's western shore. We don't know whether she will come down along the Mississippi river or go back into western Wisconsin, where she spent so much time in the fall of 2011. But we are looking forward to finding 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?

Thursday, September 27, 2012

Return to the Nest 2013: Q&A Session

Social Stream moved very quickly during the interview with Bob on Tuesday, September 25th! I wanted to publish his answers to a couple of the very commonly asked questions I saw floating around in the stream, and hopefully answer a couple that he didn't get to.

Before I start with the questions, videos are here:

What did you guys do when you installed the cam?

Bob Anderson directed the installation. He designed and tested the equipment, planned and oversaw the deployment, worked with Dave and Neil via the webcam to make sure everything was installed correctly, and staged on the ladder to help pass equipment.

Neil Rettig and Dave Kester climbed the tree. They cleaned the old camera dome, replaced the broken IR cam, removed an unnecessary screw, and added two new cameras: a new PTZ and a very high resolution fixed bullet cam. As Bob pointed out, we'll have new views. You will sometimes be able to see one of the cams appearing on screen.

Jim and Charlie worked on the computer and power protection systems and helped haul equipment.
Amy Ries briefly staged midway up the tree to help get the camera bag up, set anchors, and helped haul equipment.

What is new this year?

We have a new PTZ cam, a new high resolution fixed cam, new views of and from the nest, better surge suppression and electrical protection, new video cards, and a new system to switch back and forth between the cams on site or remotely.
Kudos are due John Howe for designing the switching system, and Kenny from Simms Electronics for his technical assistance and computer systems.

When is the cam turning on?

We don't have an exact date yet. We need to get a T1 line pulled in for faster service and make some changes to our computer system. It will be sometime between mid-October and mid-November.

When will chat re-open?

Chat will re-open in February. We will announce an exact date as it gets closer.

How did Mom and Dad react to the camera installation?

Mom and Dad weren't at the nest when we got there.  They did fly by in the early afternoon and vocalize two or three times before leaving. We saw them briefly soaring over the bluff later in the day, which was warm, windy, and perfect for flying.

Are Mom and Dad already working on the nest?

Yes, they are! They have begun adding crib rails to the side in preparation for next year's brood.

Were you able to get permission to lighten the nest? Who would you get permission from?  

The US Fish and Wildlife Service oversees permits and other issues related to the Migratory Bird Treaty Act, including falconry, raptor propagation, scientific collecting, special purposes (rehabilitation, educational, migratory game bird propagation, and salvage), take of depredating birds, taxidermy, and waterfowl sale and disposal.  We have permits to go into the nest and install cameras, and we have permits to band and attach transmitters to eagles, but we did not get permission to lighten the nest this year.

Bob pointed out that Neil, Dave, and all the gear weighed more than the eagles were likely to bring in this year, so we think the nest will be fine. We'll probably ask again next year.

Did you leave a treat for the eagles?

We usually do, but we did not this year. Fortunately, they didn't seem to hold it against us.

Is the crossbow dangerous to the eagles?

We use a dull bolt, but we also don't shoot the crossbow when the eagles are in or near the nest. We don't want to take any risks with them.

Will Mom and Dad migrate?

Probably not - they have a history of staying through the winter. Eagles are partial migrators - that is, some eagles migrate and others don't. For eagles to be non-migratory, there must be sufficient food during the winter.  The Decorah eagles have a nest in a relatively sheltered location, with ample access to food year round. The adults are not migratory.

Are D13 and D14 still around?

Yes, for D14, although we haven't seen D14 at the nest. D14 spends a lot of time NW of Decorah, near the Upper Iowa river. He has been seen in the company of other adult and hatch year eagles, but we don't know whether those eagles are family members. It is certainly possible, although there are other eagle families in the area. You can follow his adventures at: http://www.raptorresource.org/maps/D14_latest.php

Probably for D13 - D13 was believed to be spotted recently, but we don't know for sure.

Why do these eagles always lay three eggs?

They don't - in 2008, her first year at this nest, Mom laid a two-egg clutch. She has, however, laid three egg clutches every year since. Three egg clutches are not common in Bald eagles.  According to Gary Stahlmaster:
  • 79% of clutches have two eggs
  • 17% of clutches have one egg
  • 4% of clutches have three eggs
  • Less than 1% have four eggs.
Food availability impacts Bald eagles in a number of ways, although there is a lot of debate about whether or not it impacts clutch size.  Some studies say 'No', while others hint at a link. Our nests don't make it any clearer either way: one nest (the Decorah nest) has a reliable high-quality food supply in a relatively sheltered area, while the other nest (the Fort St. Vrain nest)  is at the foot of the Rockies in an area with harsh weather and a more limited food supply.  Yet the eagles at both nests have a tendancy to lay three egg clutches. We don't know why.

Are you going to turn the nightlight off this year?

No: the nightlight is infrared light, which the eagles can't see. Click here for more information on the IR cam.

Are you going to have cameras in the kestrel nests?

We don't have any plans to do so right now. The kestrel project is a pilot that explores using county right-of-ways along gravel roads to expand the kestrel population. We don't easily have a way to get power or connectivity out to the boxes, which are located in remote areas. If you would like to learn more about that project, click here.

What was that about Philippine Eagles?

The Raptor Resource Project will be working with the Philippine Eagle Foundation to raise awareness of the highly endangered Philippine Eagle. From the foundation:  The Philippine Eagle Foundation firmly believes that the fate of our vanishing Philippine Eagle, the health of our environment, and the quality of Philippine life are inextricably linked. We are therefore committed to promote the survival of the Philippine Eagle, the biodiversity it represents, and the sustainable use of our forest resources for future generations to enjoy.

We plan to add a Philippine Eagle cam and help sow the seeds for a recovery effort for and by the Philippine Eagle. We will post more about that as it gets underway.

Thank you for watching!

Tuesday, September 18, 2012

09/17/12: D14 and D1

D1 is on the move! She's roughly 77 miles of her northernmost point right now, although she's a little north of the southernmost point we've tracked her at this month.http://www.raptorresource.org/maps/latest.php

Back in Decorah, Bob took some time to track D14 this afternoon. He writes: "I had a bit of free time this AM so I tracked down D14. He was perched in a white pine tree on the top of a bluff overlooking the Upper Iowa River. There were two adult eagles perched nearby. I returned to this area a few hours later and got a beep pointing down stream. I got a booming signal when I pointed the yaggi at three immature eagles soaring high over the river. They were so high up I could not tell which one was wearing the transmitter."

D14 along the Upper Iowa River
D14 with other eagles

Wednesday, September 12, 2012

7 nestboxes in 2 days!

I've blogged a little about our pilot kestrel project [click here for kestrel nestbox plans]. We kicked it off last week when we installed the first six boxes along a rural gravel road in Bluffton, Iowa. The 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 rural ditches? Bob started talking about ditches as a sort of habitat of last resort in heavily developed areas. 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 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. Winnesheik County gave us permission to install nestboxes along 5 miles of dirt road in rural Bluffton, Iowa, and the fun began!

In the wild, kestrels nest in cavities in trees, cliffs, and buildings. They like to be up high, they want perches, and they need a fairly long box with a hole toward the top, preventing direct sunlight from reaching the box's bottom. We didn't want to use cement in the holes we dug to support the pole, since that would mean hauling water out to each site. The pole needed to be strong but also breakaway, given that it was in the county right-of-way. Bob wanted the nestboxes to have a slightly slanting roof to shed rain, sun and weather resistant siding, and a perch for the kestrels to, well, perch on. Here is what the finished boxes look like, absent a coat of paint. Bob and board member John Dingley built the boxes out of T11 siding, which we also use to construct falcon nestboxes:

Board member John Dingley with the kestrel nest boxes

Now for the posts! We weren't able to get 18’ 4x4 posts, so Bob ordered 15 green-treated 2x4 boards. He decided it would be easier to haul materials than posts, so we constructed the posts on site by gluing and screwing them to create a laminated 4x4x18' pole. Voila! Strong enough to stand against the wind, yet still break away against cars, trucks, tractors, and other vehicular interlopers. 

Bob assembles a kestrel nestbox in his mobile workshop

Last Tuesday dawned hot and humid! Bob and John borrowed a truck from camera operator Charlie and set off. The procedure went something like this: they reached a spot, stopped the truck, put up orange cones, and went to work. While John dug a fout-foot deep hole (among many other things, John is a mason), Bob built the pole, attached the pre-made nestbox, and added about two inches of sand in each box.

John digging a nestbox hole

Once the hole was dug and the box was ready, we levered the box up and into the hole. We added dirt, tamping roughly every two inches. When the hole was about half-way full, we added roughly a five gallon bucket of gravel, tmaped that, and finished with dirt. The gravel compacts extremely well - almost like cement - and provides drainage to help keep the wood from rotting.

John with an installed nestbox
The next day we installed a peregrine nestbox on a cliff just south of Bellevue, Iowa, at Bellevue State Park. We were were very pleased to find Indian mounds at the top of the cliff, just above the spot we intended to hang the nestbox. Although these were conical mounds, the Mississippian people revered the falcon and built falcon mounds. It seemed like an appropriate place to put a falcon nestbox. We were joined by Pat Schlarbaum from the Iowa DNR and Park Manager Shannon Petersen, who helped carry gear and were in general very enthusiastic about the project.

Dave, gear and mound 

Bob went down the wall to find a good spot for the nestbox. It has to be unavailable to raccoons (as usual, we found raccoon poop all over the ledges), fairly flat, high up, and visible - it can't be hidden behind foliage. Once he tagged a spot, he came up, cutting brush out of the way to make it easier to handle the nestbox. The nestbox is roughly two feet by three feet, weighs 30-40 pounds, and is constructed of T11 siding in a steel frame, which will not warp or pull off the anchors. It can be a bear to handle, especially in thick brush. The time we took to cut away branches and vines saved us a lot of work!

Bob lowered the nestbox to me, on a ledge, and I caught it and carried over to the edge, belaying it down to Dave. As usual, hazards included rocks and the box itself. Bob put a long rope on the bottom side of the box, which made it much easier for those of us below him to guide it over cliff edges and keep the box away from rocks. I got the box down to Dave and then joined him on rope, where we levered the box into place and anchored it to the wall with our awesome new hammer drill (donated by Pat Schlarbaum, thank you very much!).  Once it was firmly in place, Bob lowered down 80 pounds of pea gravel and a perch. We filled the box with the pea gravel (roughly 3 inches deep, to add drainage and prevent egg breakage), attached the perch, and got off the wall. 7 nestboxes in 2 days - done!

Dave is above the box and Amy is below it
Note: We forgot to add sand to one of the kestrel nestboxes, so Bob and John went out to fill it late last week. They saw 8 kestrels between the first box and the last box, and one box already appeared to have been claimed by a male. We anticipate banding babies here in the spring!


Resources that helped me write this article:

Monday, September 10, 2012

9/10/12: Weekly Roundup

John Carton got photographs of both recently fledged Turkey vultures! He writes: 

"The turkey vultures are now able to fly very capably with strong wingbeats, but still are staying close to their "home territory".
Presumably their parents still return to the area to feed them. One would guess that the young birds get some valuable flying practice following each feeding and emulating the departing parent; however, I have not yet had the opportunity to observe it. Today, first one and then the other adolescent left its perch, in strong flight low above the surrounding treetops, easily gaining altitude. Their flights were observably strong and accomplished."

I've been asked about whether or not the adult vultures are still feeding and/or teaching their young to fly and find food. While we don't know the later for sure (yet), John's observations indicate that the parents are still providing at least some food for their young. More of his photographs from 9/8/12 can be seen here:http://www.flickr.com/photos/johncarton/sets/72157631472408848/

D14 remains near Clermont, Iowa, while D1 is still up in Polar Bear Park, albeit on the southern end. Both Mom and Dad eagle have been seen near their nest, and we anticipate that they will stay through the winter once again. We don't have a date for cam turn on yet, but I'll post here once we do.

Monday, August 27, 2012

08/27/2: Weekly Roundup

D14bybridge I'll start with a D14 report from Bob, who writes:

"Mary and I set out to locate D14 on the Upper Iowa River down stream from Bluffton, Iowa. We were getting a strong signal with the PTT receiver as we came down into the valley near what is called the Hutchinson Bridge. As we drove over the old bridge, D14 flushed from its upper beams. He flew to a nearby tree and we were able to get some pictures. Mary and I then met with Dixie Hutchinson to show her where D14 has been on their river property. The land owner from across the river joined us just as a team of horses pulling a large wagon and making lots of noise with their hoofs caused D14 to take flight once again. We were surprised to see him join another immature eagle (D13?) in the air. He broke off and returned to land on the upper beams of the old bridge. All of us could easily see his transmitter."

We believe that D1 remains in Polar Bear Park, but have not had an update for five days. Her transmitter is solar-powered, so it is possible that grey, rainy weather has prevented the battery from charging. I'll post new coordinates as soon as we get some.

The first Turkey vulture (BB) fledged yesterday at about 10:27am. We have a Ustream video highlight here: http://ustre.am/_1GOFB:1cZn. As of this post, LB is still in the barn. I've had some questions about whether or not the TV will return to the barn after they have fledged. I don't know, but have asked for a ground update. I'll post when I get it.

For the next two weeks, we will be testing equipment, building kestrel nest boxes, and installing a Peregrine nest box at a cliff in Bellevue, Iowa. Once we have plans drawn up for the kestrel boxes, I'll post them as well.

Happy birding, online and off!

Tuesday, August 14, 2012

Turkey Vulture Musings

Some people enjoy watching the little Turkey vultures and others do not. The TVs behave quite differently from the eaglets: they spend hours a day beating each other up, don't play in a similar fashion, appear to frighten their parents (the hooligans!), and have a very unappealing diet.  They are fun to watch (if you don't mind intestinal tug-of-war) but there are not nearly as many 'awwwwwwhhh' moments. Both Bald eagles and Turkey vultures are raptors [note - I had a few of emails that pointed out this is debatable. Some experts argue that New World vultures should be placed into storks, others argue they should have their own order, Cathartiformes, and still others argue that they should be placed into raptors]. So why are their young so different? I think - and this is speculation - that the way the young birds play and interact with one another reflects their very different lifestyles as adults.

Since eagles eat live prey, they need to hunt. Since recently-killed prey has firm flesh still connected by tissue, muscle, and bone, they need to tear food. When Mom and Dad bring food in, the eaglets sometimes stalk it. Once the eaglets can stand and walk well, they also tear food with their feet, steal it from their parents and one another, and mantle to guard and protect it. Food play includes stalking, pouncing, and grabbing. A few examples:      
Turkey vultures, on the other hand, eat primarily dead food (they have been observed eating pumpkins), detectable by the smell of ethyl mercaptan.  They don't need to stalk or hunt wary prey, although they do need to eat quickly to compete with other vultures and carrion eaters, including larger Black and King vultures. I don't know that carrion or hunks of carrion could be carried to the nest without falling apart: at any rate, Turkey vultures rely entirely on regurgitation. The young don't play with food much at all that we've seen: their parents regurgitate it, they eat it, and that settles it. As John Carton noted, the chicks learn to "gulp their food properly" in response to their parents' quick in and out feedings. Eating quickly is a necessary survival skill for turkey vultures, and they don't play with their food.
Eagles build huge nests, and the young eaglets mimic Mom and Dad's nest-building activity from a very early age. They move and place sticks and other nesting material, and play tug-of-war as well (perhaps preparing for the inevitable adult differences over where, exactly, that stick should go).
Turkey vultures don't build nests the way that eagles do. In this case, the adults spent some time preparing the straw prior to egg-laying: they pecked at objects, snapped straw into smaller pieces, and formed a depression for their eggs.  However, they invested very little time in maintaining, building, or caring for it once the eggs were laid. While the young turkey vultures roam around and explore objects, they don't engage in the same kind of stick and nesting material play that the eaglets do. In this case, no nest seems to equal no nesting play.

Turkey vultures and Bald eagles are both social, and both sets of young spend a lot of time interacting with one another. When it comes to play, the eaglets tussle, cuddle, preen, steal food, and play tug of war. The young vultures (vulturelets?) beat each other relentessly, with occasional breaks for preening. While the eaglets appear to play at the complex skills of hunting, nest building, and competing for food, the young vultures appear to play primarily at competition, period. Although Turkey vultures are social, this behavior leads me to wonder about the intensity of TV to TV food competition. Is this all about other carrion eaters, or do adult Turkey vultures beat each other up over food as well?
Although the behavior of the little Turkey vultures may not be as appealing as the eaglets to human watchers, their play and interaction is equally effective at helping to prepare them for the challenges of adult life. John predicts that they will most likely begin flying between August 28 and September 3rd. I've enjoyed watching them in the nest and look forward to his observations once they have left.

If you haven't watched the Turkey vultures, you can see them at: http://www.ustream.tv/missouriturkeyvultures

Sunday, June 17, 2012

Observations of the Turkey Vultures

John Carton, Chuck Hird, and a group of dedicated Turkey Vulture watchers have been sharing and compiling information about the Turkey vultures on the 2012 Missouri Vulture Live Cam (http://www.ustream.tv/missouriturkeyvultures). Thanks to their dedication and hard work, we have these observations to date. Some of their comments are cross-referenced to the following web-accessed literature source:

This barn loft setting is in Marshall Missouri, at a barn where a pair of turkey vultures have successfully raised a hatch in each of the last three years. They have actually been returning to this loft for more years prior to the last three, however photo documentation has been accomplished only in the last three years (photos by John Carton may be viewed at http://www.flickr.com/photos/johncarton/).
Encouraged by the Missouri Department of Conservation to share information with Bob Anderson, director of the Iowa based Raptor Resource Project, the owner did so. Following a short planning process, a resolve was made by the Raptor Resource Project to establish this site as the “first ever live cam for nesting turkey vultures”. In late Fall 2011, the camera and computer monitoring equipment was installed at the site by Bob Anderson himself, with John Carton and the owner assisting. A professional electrician and neighbor on this street in Marshall volunteered all of the necessary trenching and installation of the conduit and electrical wiring.

Return of the Vultures
The first returning turkey vultures to this live cam site were observed on April 1st.

Presenting Adult Interactions
Initially several adult vultures visited the loft. Individual mature adult vultures look very much alike, so it is not possible for us to distinguish how many different individuals actually visited. On several occasions three birds were present together, and viewers reported seeing four on at least one occasion. At no time were four positively identified by a contemporary camera panning.

Gender Identification of This Mated Pair
While the physical appearance of adult male and female turkey vultures is apparently not differentiated, we are able to distinguish between the parents of this mated pair by a dark horizontal line extending across the brow of the male bird from the top of one eye to the top of the other. We know by deduction that this “distinguished eyebrow” bird is the male, only because we actively observed the egg laying by the other via this live cam. We presume this eyebrow marking is an individual difference rather than a gender distinction, however more observations of other birds is necessary.
Dad Turkey Vulture. Note the brow ridge.
Mom Turkey Vulture. Her head is smoother.

Tending The Nesting Area
On each visit to the loft, the individual vultures walked about the loft floor, each time apparently locating the straw mat area that would later become their nesting spot. While there, each repeatedly pecked at any objects on the floor mat, and repeatedly picked up and snapped into pieces the various lengths of straw. Each bird also displayed a “nest forming” behavior by squatting down on the floor litter and turning circles to create a depression. While each accomplished this behavior individually, there were several occasions when both birds were present at the same time, displaying the “nest turning” behaviors side by side. If this was in fact an interactional behavior (rather than just a parallel behavior) I had the distinct impression that it represented a relationship patterning behavior preparatory to the upcoming egg-laying and incubation periods when both parents would be called upon to tend the nest for extended relief periods (future live cam observations of the pre-egg laying period will be needed to confirm or revise this impression).
This video shows some 'nest-prep' activities:

Egg Incubation
Reference source cites incubation period of 38-41 days. My observations in prior years at this Marshall Missouri site was more like 30 to 35 days. This year’s web cam documented 1st egg laid on May 9, 2012 with 2nd egg following about May 12th.

Parenting Role Differentiation
Generally, adult vulture gender differentiation appears to be minimal.

A. Incubation related behaviors: reference source cites both parents incubate the eggs. Live cam observations confirm same. Noting that actual time measurements have not been laboriously taken, neither parent appears to pend greater or lesser time sitting on the eggs, or taking longer breaks.

B. Chick feeding related behaviors: reference source cites both parents feed the hungry chicks with regurgitated food.

Head Movements 
Periodically both adult birds have displayed rapid side to side head movements, as if a reflex movement. At times the head shakes have been as rapid as perhaps 5-6 per second, causing some viewers to speculate they were being bothered by insects or perhaps mites in their ears. Other times the head shakes have been slower frequency, one or two movements at a time, separated by several seconds between “shakes”. Occasionally in conjunction with the side-by-side head movements the adult bird has abruptly struck its beak against an adjoining wall, making a resounding “clunk” sound. I have wondered whether these characteristic head movements may have the function of clearing it’s nostrils for detection of new scents to detect potential presence of danger. When potential danger is detected, as by a sudden outside noise, the bird’s head is thrust up and it is not clear whether the side-to-side head movements accelerate at those times. More observations are warranted.

“Egg-Sitting” Patterns 
As noted above, both parents share in incubating the eggs, acting in shifts and rarely if ever both present in the loft at the same time. Typically one bird leaves alone, and later either that bird or its mate returns. The unattended time period for the eggs has generally been for as much as 20 minutes to an hour. On only one occasion, after the first egg was laid and before the second, was the egg left unattended overnight.

Egg-Turning Behaviors 
At each separation and return to the eggs, the attending parent gently turns the eggs with its beak. The method typically includes a positioning of the feet under the eggs, while extending the beak over the eggs and nudging them one at a time between the toes and on top of the feet. In the process of egg repositioning, the adult bird often moves its entire body in a rotating motion over the eggs, sometimes half a circle and sometimes completely, carefully turning and nudging each egg along using the side of its beak. This egg positioning takes place in a very deliberate unhurried manner, completed as the parent resumes sitting with the eggs nestling snugly infolded under its breast and crop area. There is no apparent gender differentiation in the egg tending behaviors between the parent birds.

Adult Interactions (Cont)
 A. Pre-egg Laying Interactions:
From the time of the vultures return to this loft, the adult birds have displayed a very minimum of physical interactions with one another. From their April 1st through the first week of May the two primary birds (that became identified as the mated pair) generally arrived individually at the loft, their arrival times ranging from as little as five minutes to as much as a half hour from one another. On other occasions one would arrive alone, remain a while and leave without our seeing the other. On nunerous occasions a third bird that some viewers came to call “limpy”, because of an apparent limping walk, was present with the primary pair. This caused speculation that “Limpy” might be an offspring of the primary pair that has still nit completely separated from them. That of course is only speculation at this time, however interesting as a possibility. In general the adult vultures presented themselves as highly independent and not inclined to any physical contact with one another. Their apparent wariness to allow any physical closeness seemed to wane after a few weeks visiting the loft, at which time they agreeably stood side by side occasionally touching at the shoulders, peering out the loft window, until one would abruptly fly off leaving the other to sit there perhaps five minutes or so before it too would leave. At no time was any actual breeding behavior observed at the nesting site. As they sat at the windows and walked about the loft floor there appeared to be some pattern of pursuit on the part of one toward the other, with a not-so-determined returned rejection by the other (viewers were inclined to dub the pursuer as the male, and the rejecting interest as the female, but the cues were always very subtle and physical appearance of male and female is very similar).

B. Adult Interactions During Incubation Period:
While both parents have tended the eggs in a similar manner, they have done so entirely independently from one another. At no time since the eggs appeared have both birds been observed in the loft at the same time, and the third bird called “Limpy” has not been present at any time. There has been absolutely no reciprocal adult bird behaviors during this time, such as one bird bringing food to the sitting bird. The sitting bird has left at intervals, which is presumed to find food for itself, and to defecate (since there is little if any sign of defecation inside the loft or around the nesting area). Rarely, if at any time has the other parent been present at the loft at the time the sitting bird requires a break. None-the-less, within 15 - 30 minutes of a sitting bird’s departure from the eggs, either that same bird or its mate arrives to resume the sitting (again without any observed interaction with one another).

Thursday, May 03, 2012

Michelle, Travis, and Peregrine Questions

Michelle and Travis hatched two young falcons on 5/13/12, and the questions are already flying! I'll try to answer a few of the most common here.

1. Why are they nesting in gravel? I wish the hatchlings had grass or something softer!
Historically, peregrine falcons nested in two places: on cliffs and in trees. To quote: "Although the peregrine falcon is currently considered a cliff-nester, records indicate that it once nested in tree cavities (Goss 1878, Ridgway 1889, Ganier 1932, Bellrose 1938, Spofford 1942, 1943, 1945, 1947, Peterson 1948). The peregrine still uses cavities in broken-off trunks in Europe (Hickey 1942), but the hole-nesting population of America apparently disappeared with the felling of the great trees on which they depended (Hickey and Anderson 1969)."

Either way, peregrines did not build nests out of branches, twigs, or grasses. Cliff nesting birds use ledges or potholes. These commonly have some kind of substrate: sand, pebbles, dirt, and so on. The male and female dig and wiggle out a scrape, or shallow cavity, into which the female lays her eggs. The substrate provides drainage, cups the eggs, and helps keep them from breaking on the edges of the underlying rock. We use 80 pounds of pea gravel in our nest boxes to simulate a substrate and protect the eggs.

2. How long can the babies go without eating?
The hatchlings consume the egg yolk shortly before hatching, which gives them enough nutrition  for 24 to 48 hours. However, they don't usually have to go very long. Their first feeding was at 11:49am CST this morning.

3. What do falcons eat?  Falcons eat other birds. We've found the remains of pigeons, woodpeckers, coots, finches, blackbirds, ducks, cuckoos, and many other birds stashed in and around nests. In general, the adults catch a bird by diving or stooping on it. If the impact doesn't kill it, the adults use their tomial tooth - a notch in their beaks - to bite through their prey's cervical vertebrae. They pluck their prey prior to eating: "feather falls" have helped me locate Peregrine falcons at the Mayo Clinic and the Dairyland Alma power plant. 

Adult peregrine falcons eat about 2 1/2 ounces (70 grams) of food per day. Using a rough back-of-the-envelope calculation, males average 587 grams of weight and females average 1205. So males eat roughly 11% of their body weight each day. I'm guessing - and this is a guess - that females do the same, so Michelle probably eats a little more than Travis does. It has been speculated that  gender-based size differences allow male and female birds of prey to eat from a slightly different prey bases, widening the available food supply.

So based on this calculation, I'd need to eat about 16.5 pounds of food every day to keep up with Michelle.

4. How fast will the babies grow?
Peregrine falcons double their birth weight in 6 days, and are 10 times hatch weight in three weeks.
Like the eaglets, they start with a fluffy white coat of baby down. We'll start to see brown juvenile feathers emerging at about 20 days of age. By 40 days, the young birds will be sleek brown juvenile falcons.

Over the next few weeks, we'll see a lot of eating, sleeping, and pooping. Poop is a great way to locate the nests and perches of many kinds or birds. See bird poop? Look around for the bird!

5. Will Cain and Abel Syndrome be a problem here?I don't want to say 'No', but I haven't seen it at any of the other Peregrine falcon nests we watch. There is an ample food supply and Michelle and Travis are very good at caring for their young.

6. Mom and Dad are talking to the babies!
Yes, they are! We've already heard Michelle echupping encouragingly to her young immediately before their first feeding. We'll also hear the young food begging (which one website describes as 'screea screea screea'), and kakking: an alarm, defense, and 'annoyance' call. Peregrine falcons are  very vocal. I've had unhappy babies set my ears to ringing more than once.

7. Does the nest smell bad?
It depends! Some falcons are great housekeepers, while others (I'm looking at you, Hibbard plant falcons) let prey remains pile up in the nest. If the nest is messy, the young birds smell interesting to human banders - not bad, but not pleasant: a complex, spicy smell.

Things that helped me learn and write about Peregrine falcons:

Friday, April 27, 2012

Watching Bald Eagles

Bob took a turn operating the controls at the Bald eagle camera this morning. He was fascinated by Dad, who brought in three suckers in one hour. Suckerfish are 'rough' fish: generally considered undesirable by humans, they have large scales, fleshy lips, and a 'sucker' mouth that is wonderful for attaching to rocks and scouring river bottoms for food. They spawn in shallow water during the spring, when water temperatures reach between 47 and 60 degrees Fahrenheit. The Iowa DNR tells us that males move upstream in large schools, congregating and defending spawning territories that contain gravel riffles and rubble shoals. While suckers are spawning, eagles are raising a family. Suckers make easy prey: they are relatively exposed, there are a lot of them, they congregate in one area, and they don't leave until spawning is done. "Think about it," Bob said. "We are watching them eat food they evolved with over eons."

Bald eagles have several excellent adaptations for fishing. An eagle's powerful toes, locking talons, and spicules - tiny projections on the bottom of its feet - help it grasp and hold slippery fish, as do the serrations on the roof of its mouth. The black pigment on its wing feathers strengthens them against breakage when it dives into the water. Its nictitating membrane and the boney ridge over its eyes - so noticeable in Mom - helps protect its eyes from sunlight and reduces glare. Bald eagles eat a wide variety of prey, but they are fishers par excellence.

So how old are Bald eagles as a species? Birds begin to appear in the fossil record between 144 and 66 million years ago. These ancestral birds gradually diverged into separate species. Kites, the ancestors of today's Acciptiridae, emerged tens of millions of years ago. Like modern eagles (but not all Acciptiridae) they are believed to have scavenged and hunted fish. The first eagles descended from kites roughly 36 million years ago, and the earliest known fossil remains that closely resemble the bald eagle date back to about a million years ago.

Plio-pleistocene Bald eagles in North America might have shared the landscape with mammoths, dolichohippine horses, camelops, glyptotherium, terror birds, and stegomastodon, as well as more familiar bats, birds, rodents, and fish. Did they build the same kinds of nests? Did they raise their young the same way? Did eagles feed on suckerfish even back then? We don't know: birds don't preserve very well. Still, the thought that Bald eagles flew over an ice-age North America gives me the shivers. So much of what was is gone now, but eagles and sucker fish are still with us.

Fast-forward to a shallow stream 15,000 years ago. Suckers are making their way upstream to spawn. Suddenly, an eagle swoops down and hooks one to bring to its waiting young, who are clamoring hungrily in the nest above. Dad has food. His legacy will survive into a future he can't imagine.

Things that helped me learn and write about this topic:
It was fun to read about plio-pleistocene life forms. It reminded me of very loved books from my childhood that I haven't thought about in ages: brightly colored children's science books about the ice age with fantastic illustrations of mammoths, saber-tooth tigers, and so much more. What a treat to think of them again!

Monday, April 23, 2012

They Grow Up So Fast!

The eaglets in Decorah are 27, 26, and 24 days old. Their darker second down has been in for days, and pinfeathers are beginning to show on the edges of their wings, signaling the emergence of their first juvenile contour feathers. Here is how it works. Each feather arises from a feather follicle in the skin. The pin feathers, or feather follicles, contain undeveloped contour feathers. As the contour feathers develop and emerge from their follicles, they push the down feathers off. The down will remain attached to the contour feathers until it rubs off.

Other changes: the eaglets are more proficient at walking and pooping. They are a lot bigger, although their growth curves (when expressed in weight gain per day) will begin slowing sometime in the next three to six days. The overall size of their footpads should already have started slowing down but the growth of their juvenile contour feathers is just taking off : like many animals, parts of the eaglets' bodies grow at different rates.

If human children play house, the eaglets are playing nest. We've seen the eaglets tussle with cornhusks, move debris around the nest, nibble on everything from food to mom's tailfeathers, 'attack' prey, and explore. Socially, they spend a lot of time interacting with one another and with their parents: they alternately dominate and cuddle, observe Mom and Dad (especially when food is involved), and 'help' with nest chores. This behavior is all part of their growth and development. We sometimes think of play as being unimportant or trivial, but play lets young animals 'practice' the skills they need for adulthood, cements bonds between players, and is pleasurable to those playing.
Here are some videos that show our eaglets growing, playing, and practicing:
Sherri Elliott's daily 'Whattas' on our facebook page provide a wonderful round-up of eaglet daily and developmental events: https://www.facebook.com/pages/Raptor-Resource-Project/103786266324668?sk=notes. I wasn't able to find any information on Bald eagles and play, but here are some play links worth looking at.
I think we should all get out and play after this post is done!

We've been asked how soon we can tell if the eaglets are male or female. The short answer is that we can't tell for sure unless we capture them and take measurements or a blood test. Having said that, Gary Bortolotti notes that sexual dimorphism begins to appear in some variables after 20 days of age. Initially, size depends more on hatch order than anything else, but after 20 days, gender begins to play a role. Females are bigger than males and have correspondingly wider wingspans, bigger feet, and thicker tarsi. Without proper measurements we are speculating, but speculation is part of the fun.

Bob is anticipating that fledge will happen mid-June: a little less than two months from now. Over the next few weeks, we'll see the eaglets get bigger. Dark brown juvenile feathers will replace their fuzzy grey down and we'll see even more wingercizing and play as they transition from nestlings to flighted hunters. Have fun watching!

We are also waiting for the Great Spirit Bluff Peregrine falcon nest to begin hatch on May 2nd, and the Turkey vultures to lay sometime between May 1 and May 7. There will be a lot to see, laugh at, and learn from.

Things that helped me learn about and write this post:

Tuesday, April 17, 2012

Birds and Weather

We've heard a lot of concerns about weather from nest watchers.  Following the nicest March anyone in the American Midwest can remember, we've had tornado outbreaks, high winds, damaging storms, large fires, and snow. The Decorah Bald eagle nest has been tossed around by wind, the Fort St. Vrain eaglets died of exposure following a spring storm, and the Dairyland Power Genoa cam was damaged by lightning. We get asked daily if we can't do something about the weather: shore up nests, build roofs, and even take young birds from their nests. The short answer: No. I wrote about intervention in an earlier post. We intervene in the case of obvious, acute danger, but weather is a chronic condition that all of us have to live with.

High winds, severe storms, and fire are nothing new. If animals couldn't survive them, they wouldn't be here. The birds we watch are well prepared for the weather challenges they face.
  • It's Cold and Wet! Feathers are wonderful insulators and adult Bald eagles have roughly 7,000 of them. Light and fluffy down feathers trap air, while flight feathers hook together like a zipper, forming a continuous 'vane'. Preening releases an oil that coats the outer layer of feathers, which further protects adult birds from moisture: the outer feathers may get wet, but the bird's body does not. We've watched the adult eagles shake off rain and sleep under a blanket of snow. They are well prepared for cold, wet weather.

    As of this post, all of the Decorah eaglets have their second down. Unlike the first fluffy white down, the 'wooly' second down has insulative properties. Mom and Dad will still protect the eaglets from rain and snow, but they are able to thermoregulate now.
  • It's Hot! We've had a lot of questions about panting this spring. Like dogs, eagles don't have sweat glands. They control heat by panting, radiation through their unfeathered legs and feet, and perching in the shade. March was unusually warm and the cottonwood doesn't leaf out until April, so the eagles spent a lot of time in direct sunlight. We also got to see a little more of the eaglets than we usually do: many cam watchers commented on how lively, naughty, and busy this year's brood has been. The dry, hot weather means that the eaglets spend more time exploring the nest than huddled under Mom or Dad, and everyone spends more time panting.
  • It's Windy! Adults and young hunker down against high winds and storms. Some of their behavior appears instinctive and some is learned. The first year Mom nested here, she turned tail to the wind and was blown out, nearly taking a young eaglet with her. That hasn't happened since. The adults minimize their profiles during high winds, keeping wings tucked in, tails low, and young birds protected. Young birds curtail nest exploration and play, sheltering under Mom or Dad until the wind dies down.  When the adults do get pushed around by sudden wind gusts, they don't grab at the eaglets, and the eaglets are not especially aerodynamic at this point.

    We've also heard from watchers concerned that the Decorah Bald eagle nest will fall/has fallen. The nest weighs approximately 1300 pounds, is tightly woven of strong wood, and is wedged securely into the limbs of a cottonwood tree. The tree is healthy, with no large dead limbs, and near a good water source.  Can we say that the nest will never fall? No. But is it likely to fall? Also no. The nest is very secure and the tree is healthy and relatively secluded from wind. If the nest or tree did go down, we'd be on site as quickly as we could.
In short, we can't do anything about the weather. Fortunately, the birds we watch are equipped to survive it in all but the direst cases. The Decorah nest in particular benefits from an ample food supply, experienced parents, and a relatively sheltered location. Last year, we watched them respond to cold weather and late snowstorms. This year, we've watched them respond to warmer, windier conditions: they've spent more time off the eggs and young babies, and their 'hunker down' time has been more likely to be a response to wind than rain or cold weather.

Here are a few videos that show the Decorah eagles under various weather conditions:
Things that helped me write and learn about this topic:
If you would like to learn more about how animals survive cold weather, I highly recommend Winter World: The Ingenuity of Animal Survival by Bernd Heinrich. If you would like to know more about animals in summer, I highly recommend Summer World: A Season of Bounty, also by Bernd Heinrich.