Thursday, December 26, 2013

Birds and Daylight Length

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

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

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

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

Some exploration points:
  • Is there a predictable increase in frequency of nest visits as daylight length increases?
  • Do Mom and Dad differ in their nest building behavior? 
  • Do Mom and Dad spend more time interacting as daylight length increases?
  • Does weather also appear to impact nest-building activities?
I would love to hear from any teachers that end up exploring any of these points in the classroom. Email me at and let me know about it, or friend us and share it on our facebook page:

Some reference materials:
  • Living on the Wind: Across the Hemisphere with Migratory Birds (thanks, Joan!)
  • Adaptation and evolution of photoperiod response systems in birds (
  • Explanation of the word Recrudescence (I didn’t know Senescence had an antonym!):
  • Photoperiodism: Deep Brain Light Reception:
  • Photoreceptor Cell:

Wednesday, December 11, 2013

Lead Poisoning, Toxic Shot, and Lead-Free Hunting

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

So how serious is lead poisoning? SOAR has wonderful information on their website at A few figures that struck me:
  • 56% of all eagles admitted to Iowa rehabilitators between 2004 and 2008 had abnormal lead levels in their blood. This ranged from a low of 37.5% in 2004 (with 62.5% of eagles being tested) to a high of 70.0% in 2005 (with 90.0% being tested).
  • The University of Minnesota’s Raptor Center in St. Paul received 117 lead-poisoned bald eagles during the winter of 2009.
  • While lead poisoning can kill directly, as it did with the eagle we tried to rescue, lead toxicity is also a factor in collision deaths and injuries. According to the Raptor Center, about 85% of eagles that come in with collision injuries also have elevated lead levels. This video from the UK shows the effects of lead on a duck's coordination and motor skills:
Lead poisoning is primarily the result of exposure to leaded or toxic shot. In 1991, the US Fish and Wildlife Service banned lead shot in waterfowl hunting, although it can still be used for some other types of hunting, depending on your state's laws and regulations. A survey of ducks on the Mississippi Flyway found that the ban on lead shot reduced lead poisoning deaths of Mississippi Flyway mallards by 64 percent, while overall ingestion of toxic pellets declined by 78 percent over previous levels. By significantly reducing lead shot ingestion in waterfowl, the ban prevented the lead poisoning deaths of approximately 1.4 million ducks in the 1997 fall flight of 90 million ducks.

Did the ban on lead shot prevent successful waterfowl hunting? No. The total number of geese and ducks harvested nationwide declined steeply beginning in about 1984, but started rising again in roughly 1992, as shown by this chart: Requiring the use of non-toxic shot did not negatively impact waterfowl hunting, but did prevent ducks, geese, and many other animals from coming into contact with lead shot by ingesting it directly or feeding on lead-poisoned animals or carcasses containing shot.

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

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


Friday, October 25, 2013

2013 Decorah Eagle Cam Questions

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

Where are Mom and Dad Decorah nesting?
They are nesting in the new or yonder nest, henceforth to be known as N2. N2 is about 533 feet or 162 meters east of N1, by the side of Trout Creek. It is 60-70 feet up in the center fork or crotch of a cottonwood tree. The image below shows both nests and the trout hatchery.
N1 and N2. The eagles are currently nesting in N2.
Click the image for a larger view.
What is the diameter of N2?
We didn't measure it exactly, but it is smaller than N1. I'd guess about 4 feet in diameter. This yields a circumference and area of about 12.5 feet. Neil and I were just barely both able to fit into it, and we hung all of the equipment of the side with leashes and anchors.

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

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

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

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

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

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

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

Did you work on N1's cams?  If so, did you see anything that would help speculate on why they left N1?
We didn't go up into the tree - those cams are still running from 2012. We don't know for sure why they left, but there are two theories.
  • Theory one: That's what eagles do. In one study of 318 eagle territories in Alaska, 45% of eagles studied had more than one nest on their territory. In another study of 924 territories, eagles were found to have an average of 1.5 nests in their breeding area. N1 was built in 2007. Maybe it was simply time for them to build a new nest. We all know how much time they spend working on the nest.
  • Theory two: The old nest was built farther out along the branches of the cottonwood. Its weight was causing it to tilt toward the outside. This could have caused the eagles to abandon it in favor of a new nest. 
I'm more in favor of one, myself, but I'm not ruling out two. For more speculation, check out this blog post:

Coming down the tree
How did you get into the tree?
After making sure no eagles were in the area, we fired a crossbow loaded with monofilament line over our target branch. We used that to pull a four mm cord, which was used to pull an 11mm climbing line. Neil used a frog system and I used a grigri + ascender + carabiner. Neil got up into the nest in about a minute. It took me a little longer. Here are two video links that show the basic technique:
Coming down was interesting since Neil's rope wanted to pull him away from the tree. We wrapped webbing behind him and I pulled him into the tree so he could run the cable. This worked extremely well.

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

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

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

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

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

Red-Tailed Hawks and Social Play

Eaglecrest facilitator mochamamma has captured several videos of young red-tailed hawks squabbling, chasing, and stealing food from one another.
At first we thought they might be nest mates – although Stitch and Spot hatched just one young hawk, there are other nests in the area. But as the hawks piled up – three, four, five, eight – it became increasingly clear they weren’t related. What was going on?

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

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

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

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

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

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

Wednesday, September 04, 2013

Golden Eagles

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

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

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

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

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

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

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

Things that helped me write about this topic:

Thursday, August 22, 2013

Getting Wet!

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

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

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

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

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

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

Some more things that helped me learn about this topic:

Wednesday, August 14, 2013

Kestrel Nest Box Update

The American kestrel prefers open areas with short ground vegetation such as grasslands, meadows, fields, and parks. In urbanized areas, they might be seen perched on a pole or wire overlooking open space below them. They feed primarily on small animals, including grasshoppers, mice voles, dragonflies, and small lizards. If you have suitable habitat and would like to install a kestrel nest box, click here for our plans. We'd love to hear from anyone who has installed one of our boxes, so shoot me an email and let me know:
Last year we began a pilot project to install kestrel nest boxes along rural gravel roads. The American kestrel (Falco sparverius) is a small falcon that is in decline throughout parts of its range. There are a number of theories about the kestrel's decline: HawkWatch International's list of factors includes development and reforestation of preferred habitats, poisoning, and the West Nile virus. We've focused on the loss of grassland in Iowa, where farms have grown larger, woodlots, fencerows, and fallow land have shrunk, and small grains and hayland have been replaced with row-cropped soybeans and corn. The Iowa DNR states:

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

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

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

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

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

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

Sunday, June 23, 2013

Great Spirit Bluff Peregrine Falcon Update

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

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

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

Absent external stimuli, Bob has never seen young falcons jump from a nest box or cliff as they did at Great Spirit Bluff. He believes that insects caused the young falcons to stampede from the box. Just a few weeks ago, 17 of 20 adult whooping cranes in central Wisconsin deserted their eggs due to black flies, as reported in the Wausau Daily Herald.

Please refer to this blog post for more information about insects, intervention, and fosterage:

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

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

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

Tuesday, June 18, 2013

Great Spirit Bluff Falcons: Intervention, Insects, and Fosterage

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

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

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

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

So now we needed to decide what to do with Jonathan, the young falcon that was recovered. He was seemingly healthy. Did we want to put him back in the box? Bob decided against it, since he thought it was highly likely he would leap again. We looked at nests with falcons that were the roughly the same age. Red Wing Grain had two falcons only about a day apart in age. We decided to foster Jonathan because: 
  • Jonathan was unharmed and should be kept in the wild if at all possible.
  • All four falcons abandoned the box due to flies or gnats. Even with treatment, the problem seemed likely to happen again. Since we haven't seen as severe a problem with the falcons at Red Wing, it seemed likely that fostering or augmenting Jonathan would give him the best chance at survival.
  • Fostering/augmenting is a proven technique that was commonly used in the early days of falcon recovery. Bob used augmentation a number of times in the early days of falcon recovery. Adult falcons don't count young, so as long as everyone is roughly the same age, augmentation can be used to introduce young falcons into the wild. 
Bob will most likely be fostering/augmenting Jonathan on Wednesday morning (he will keep Jonathan in his mews for a little observation prior to release). It seems likely that our pattern of disappearing and dying young falcons might be caused by insects and parasites in some combination - a "mega-hatch" caused by the late, wet spring. We'll let you know what we find out. 

We have some film clips here: 

Monday, June 03, 2013

Avian Parasites

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

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

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

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

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

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

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

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

Friday, May 31, 2013

I Found A Baby Bird...Now What?

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

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

By animal:
By zipcode and location:
By state:

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

Thursday, May 30, 2013

IR Reflective Feathers and Facial Disks

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

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

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

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

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

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

Wednesday, May 22, 2013

The Riverside Herons, Xcel Energy, and Rob MacIntyre

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

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

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

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


In addition to being silent flyers, owls are remarkably cryptic. This photo shows a barn owl, possibly mother Tess, perched just outside the nest cavity. She has flattened herself against the tree and is holding one wing down. Her barred wings break up her outline, making her difficult to see against the tree's rough bark.

Camouflage exists in two basic forms: crypsis and mimesis. Cryptic camouflage makes animals hard to see, while memesis, or mimetic camouflage, disguises them as something else.

Visual crypsis can be achieved in many different ways. When Tess is perched as she is above, her colors and patterns resemble a natural background. Owls are adapted for exceptional camouflage when roosting and hunting. Many species have colors and patterns that mimic the bark of preferred trees, which may explain the incredibly variety of color and pattern morphs seen in many widely distributed owl species.

Disruptive patterns use strongly contrasting, non-repeating markings such as spots or stripes to break up outlines. Tess's barred wings, plumage, and dark spots help break up her outline, making her difficult to see. Her spots also make her more attractive to male barn owls, who exhibit a clear preference for spotted females. The bigger and darker the spots, the better!

Cryptic patterns and coloration don't work as well when an animal is moving. While the fledgling owls aren't acting particularly cryptic, adult owls have very cryptic behavior. They perch quietly and hunt stealthily. Their soft feathers reduce turbulence, muffling the sound of air flowing over their wings. As the young owls learn how to fly and hunt, they will become increasingly cryptic as well.

The combination of stealthy coloration, disruptive patterns, and cryptic behavior make owls very cryptic, or hard to see. But some people believe that kestrels practice mimetic camouflage. The picture to the right shows the kestrels nesting at Xcel Energy's Pawnee Station earlier this year. The male is on the left and the female is on the right. They are facing forward, so we can see the dark 'eye spots' on the back of their heads. This mimetic false face might confuse predators into thinking that the back of a kestrel's head is actually its front.

Like many ground-nesting birds, Killdeer lay very cryptic eggs. I find it extremely difficult to see the Killdeer egg in this video, even though she lays it right in front of us (it can briefly be seen about 52 seconds into the video). Both of the adults are quite cryptic against the gravel road. However, they also practice a distraction display that disguises a healthy bird as an injured one and helps protect the nest. When a threat approaches the nest, the killdeer holds it wing in a position that simulates an injury and emits a distress call. The 'injured' killdeer lures the predator away from the nest by appearing to be easy prey. Once the predator is far enough away from its nest, the killdeer flies away. This behavior also strikes me as mimetic, since a healthy bird is mimicking an injured one.

Can you see the Killdeer egg in this picture?

Tuesday, May 21, 2013

Barn Owls Fledging at Eaglecrest

The barn owls began fledge at Eaglecrest on 5/19/13, when the first barn owl decided it was time to leap from the nest. We wondered how fledge would work, since the nest was so tight. The internal diameter of the hole is roughly a foot and a half, yielding a total area of about 1.76 feet (A=pr2) for four to five rapidly growing owls. In general, the birds we watch spend time wingercizing and hopping before fledging, learning about their wings and building some muscle prior to their first flight. But the size of the nest cavity prohibited the young barn owls from getting wing practice in. Would the lack of wingercizing present a problem? The answer appears to be 'No'. After sticking its wing out of the hole and clambering back in, the fledgling owl stuck its feet outside the hole, looked around, lowered its head, and leaped out into the night. This video shows the owl rapidly winging away from the tree, while three or four siblings watch from the hole. Actual fledge happens at 8:35 into the video.

Over the last two nights, we have watched the young owls begin to learn the basics of flying. They hop on branches, clamber up and down the trunk, and spend time practicing on the former canada goose nest, hopping and flying from the trunk to the nest and back again. We've also seen them scanning, moving their heads back and forth as they look at and listen to the world around them. Earlier this year, I was talking to one of my children about her navigational skills. "Mom," she protested, "why would I know how to navigate?  I've lived in the same place my whole life, and I don't drive yet." I think the young owls may be having a similar experience. They've spent their entire lives to date in a small, crowded hole where their wings and directional hearing weren't really needed. They have roughly five weeks of diminishing parental care to learn  flying, pouncing, hovering, hunting, and capturing prey. While flying and hunting are instinctual, proficient flying and hunting must be learned. A few video highlights from the first couple of nights:

According to the Barn Owl Trust, the amount of food each owl receives from its parents diminishes to zero by 14 weeks. There is some disagreement about dispersal, which may or may not happen after 14 weeks. We'll see what this family does.

Not a night owl? I am freeing up video from each night on a daily basis. To watch video, go to  Eaglecrest's Ustream site. Social stream will most likely be open. Click the Video tab just left of the Social  Stream tab above SS to view video.

Friday, May 17, 2013

Happy Endangered Species Day!

While we are perhaps best known for our work with web cams, the Raptor Resource Project was incorporated as a 501c3 in the late 1980s to help return the then highly-endangered peregrine falcon to the wild. In honor of Endangered Species Day, I'm going to talk a little bit about peregrine falcon recovery and our work with peregrine falcons. Many, many people worked to recover the peregrine falcon, and I don't mean to short any of them. But this post talks specifically about our work.

The Setting

In the late 1940s, biologists began noticing precipitous declines in the populations of many predatory birds. The cause of these declines was not identified until the mid-1960s, at which point several raptor species, including the Peregrine falcon, were facing extinction. DDT, a widespread, extensively-used pesticide, was interfering in eggshell formation. Seemingly healthy birds were laying eggs so thin that they were literally crushed to death by the weight of the incubating adult. How drastic were the effects of DDT? In the early 1940s Joseph Hickey, a Wisconsin biologist, determined that there were more than 200 pairs of Peregrines east of the Mississippi River. But by 1968 there were no Peregrines east of the Mississippi river at all. By the mid-1970s, the population had dwindled to 19 pairs in the western United States.

Dan Berger's Notes
Project friend Dan Berger was deeply involved in charting the species' decline in the 1950s and early 1960s. Dan worked with Fran Hamerstrom, Aldo Leopold's only female graduate student and a great conservationist in her own right. The falcon-finding team drove slowly along the (then gravel) roads by the Mississippi in an old van that had been retrofitted with a large plywood platform. One team member would lie on it and look for falcons. When a falcon or likely cliff was spotted, the team stopped to explore.

Now we use 11 mm static ropes and a variety of climbing equipment to get to eyries. But none of that existed in the 1950s. The team purchased hemp rope from hardware stores and used it to build ladders, which they used to access nests hundreds of feet off the ground. Their work made it clear that the peregrine falcon was in decline.


The Peregrine’s return to American began with the formation of the prestigious Peregrine Fund at Cornell University. Led by Dr. Cade, the Fund pioneered techniques of captive breeding to produce young peregrines for release. Although many opposed the idea, Dr. Cade persevered and by the mid-1970s began releasing captively-produced peregrines using a falconry technique known as hacking. Following the lead of Dr. Cade, other groups in the United States and around
the world began to breed and reintroduce peregrines.

Bob Anderson became interested in falcon recovery in 1972, when he was working at the Science Museum of Minnesota. He produced his first falcon in 1975. Peregrine falcons were very highly endangered at the time, with only about a dozen pairs left in the wild in the United States, so he began breeding Prairie and Gyr falcons, which were more common. . In the early 1980s, he sold his home in White Bear Lake and all of his 3M stock to begin his breeding program. He often says that successful breeding required a 24x7 commitment. When I met him, he was feeding young peregrines every four hours around the clock.

Weighing an egg
Very little was known about how to successfully breed falcons and incubate eggs, so the people involved in it were creating a new discipline. They shared information on what did and didn't work, including artificial insemination, incubator conditions, semen collection, breeding birds, and caring for young. Eggs were measured to determine weight and measure water loss. Bob was checking the egg to assure incubator humidity was optimal for hatch. With only a handful of peregrine falcons left, any loss was a big one.


Young falcons were released using a technique called hacking, developed by falconers to improve the hunting and flying skills of falcons raised in captivity. Young birds are released from a hack box, which provides some shelter for them. Since the falcons don’t have the hunting skills they need to provide for themselves, food is put out on a hack board. As the young falcons become proficient hunters and flyers, they eat less of the food provided at the hack board, and feeding eventually becomes unnecessary. This mimics the care that parents provide in the wild.

In falconry, the birds are re-trapped. Since the goal in this case was release, none of the birds were re-trapped. All of the birds we watch in the midwest today are the descendants of captively-bred and released falcons. Without the people who bred them for release, we wouldn’t have falcons to watch in the wild. While many of the people who worked in falcon recovery were academic, others were enthusiasts who believed they could recover the species through hard work and diligent care. Working together - and a lot of people from all walks of life worked to recover the falcon - they did!

Very early releases in Minnesota and Wisconsin were done in wild places. There were attempts – some successful and others not – to hack birds at Maiden Rock and a nameless bluff just south of Nelson, Wisconsin, and at Weaver Dunes in Minnesota. Following a failed attempt at Weaver Dunes, it was decided that all releases would be done in the city.

In 1987, just two peregrine falcons were produced in the
wild  in the mid-continent. Banding season lasted
less than an hour. 
This is MF-1. Produced by Bob Anderson in 1985 for the Minnesota Falconer’s Association, in 1987 she became the first bird to return mid-continent and breed in the wild. She nested on the Multi-Foods tower in Minneapolis, MN from 1987 to 1994.  He attributes his production success to good breeding stock. The issue of breeding stock was somewhat controversial. Since the original population was almost gone, it had to be recovered from a variety of subspecies, including some that had never nested in the area. Bob acquired breeding stock that was as close to the original anatum as he could get, since he believed they were more likely to survive.

Power Plants

In 1989, an employee and falconer named Paul Simonette reported a falcon at Xcel Energy's Allen S. King plant. Bob verified the report and approached Xcel Energy about putting a falcon nest box on the stack, at the 400’ level (ring two). They agreed and the Utility-Peregrine Program was off and running.

Belinda currently lives on ring two. She's a real monster.
Peregrine falcons provide wonderful organic pigeon control, and the company quickly became interested in boxes at their other facilities. They were joined by many other power companies, including Minnesota Power and Light, Dairyland Electric Cooperative, and Alliant Energy. Since 1989, over 1,000 falcons have been produced from power plants ranging from MPL in Cohasset, MN near the headwaters of the Mississippi river, down through the  Portage de Sioux Power Plant in St Charles County, MO. Power companies also played a crucial role in returning the Peregrine falcon to the wild, and especially to the Mississippi river valley.

The River Valley

In the mid-1990s, Bob started to wonder why peregrine falcons weren't returning to historical cliff eyries. We witnessed falcons fighting to the death over nest boxes not far from historic eyries that were home to the original population. Why weren’t they using the cliffs?

Bob began to think that the falcons were imprinting to buildings. He proposed a series of cliff-based releases to address the problem. It was 1996 and the idea was controversial. Only 55 falcons had been produced in the wild in Minnesota, Iowa, and Wisconsin, and the species was still quite endangered. Pat Schlarbaum from the Iowa DNR was very interested in Bob’s hacking proposal, so Bob sold his place in Hugo, Minnesota and moved to Iowa to breed and hack falcons.

This is the eyrie, built into the side of a house
Bob and several friends and Project members, including John Dingley and Dave Kester, built a special eyrie on the side of his house in which to raise the captively-bred falcons for release. The eyrie was built to resemble a cave and looked out on a natural landscape. The young falcons were raised in this chamber with as a little human interaction as possible until they were ready for release.

After an initial test release in Bluffton, Iowa, it was time to work on the Big River. Bob chose Hanging Rock in Effigy Mounds National Monument because it met all of his criteria. It was along the Mississippi river, highly visible, and in a region that contained several historic eyries. However, it wasn’t in his back yard. We hacked falcons from Effigy Mounds National Monument in 1998 and 1999. It was an arduous process that required a 100-mile round trip and three-mile mosquito-infested hike along a muddy, narrow trail every day, for over 40 days each season. The young falcons were fed and counted every day.

I returned to Effigy Mounds in 2010 and hiked out to Hanging Rock. The trail is a lot nicer now.

Return to the Cliffs!

In the spring of 2000, Bob learned that one of the falcons we had hacked at Effigy Mounds had been spotted on Queen’s Bluff, a historic eyrie south of Winona, Minnesota. He was thrilled! Our experiment had been a success. Although we’ve now seen falcons from buildings go to cliffs, and falcons from cliffs go to buildings, crossover did not begin until we created cliff-imprinted falcons. By hacking falcons from cliffs, we’d created falcons who were programmed to return to them. Other falcons would follow.

This photograph shows the female perched on a snag. Bob and I hiked up the back of Queen’s Bluff when I was four months pregnant with my son, who is now 12 years old.

The returned population of peregrine falcons is probably the most documented the world has ever known. Every spring we work out a banding schedule, load up gear, and head out to power plants, stackhouses, water towers, buildings, and cliffs. In 1987, two peregrine falcons were produced at one site. This year, we will be banding at roughly 40 sites, including power plants, water towers, stack houses, and cliffs. We climb, rappel, and scramble like crazy to get all of the work done. Because of falcon banders, we have a life history on every bird we can identify that stretches back to the founding population. Organizations that band falcons in the midwest include the Raptor Resource Project, the Midwest Peregrine Falcon Society (who also maintains a wonderful database), and the Wisconsin Peregrine Society.

Helping Species

The peregrine falcon was removed from the federal Endangered Species List in 1999. Its recovery was a true success story, since it showed that dedicated, passionate people could make a difference for the better. However, other species are still in need of our help. Visit the Fish and Wildlife Service Endangered Species Day website for more information, or check out this map (thanks, Nora H!).

We can make a difference!

We stand on the shoulders of giants. I would like to encourage everyone to learn more about two relatively unsung American conservation heroes, Fram Hamerstrom and Althea R. Sherman  (I would be happy to see posts about conservation heroes everywhere in the comments). They made a difference. You can too!

  • Fran Hamerstrom (and Dan Berger and many others): A book: Mice in the Freezer, Owls on the Porch. You can buy it from Amazon. Fran Hamerstrom was amazing! 
  • Althea R. Sherman: A book: Birds of An Iowa Dooryard. Amazing observations from a woman who did not begin her career as an ornithologist until she was 50 years old. See also this website: 

Saturday, April 27, 2013

Avian Infanticide

On April 24th, the turkey vultures in Missouri laid their first egg. The egg was captured by video-maker Priscillash and celebrated by cam watchers. We were all perplexed when the egg disappeared. What happened to it? A quick review of footage revealed the culprit - a male turkey vulture. He spent roughly 20 minutes rolling, banging, scraping, rubbing, and biting the egg on and off camera view. The barn's owner was not able to find the egg or eggshells, so we assume the vulture consumed the egg after cracking it.

This behavior appears to be infanticide. Although we haven't seen it at the nests we watch, it is not an uncommon behavior in birds. Avian infanticide may involve killing eggs or hatched offspring. It includes:
  • Exploiting young as food
  • Sexually-selected or paternity-influenced infanticide
  • Resource competition
  • Social pathology, gender selection, reproductive fitness
We've seen falcons and eagles exploit dead young as food, although we haven't seen them kill young for food - the difference between infanticide and cannibalism. In the case of the bald eagles at Fort St. Vrain, and the falcon Belinda at the Allen S. King plant, the dead young were readily available and the live young needed feeding. Although it seems awful to many human watchers, exploiting dead young as a resource very probably saved live young, especially at Fort St. Vrain, where the eagles were struggling with cold weather and a heavy snow fall that reduced food availability.

The vulture destroys the egg
The turkey vulture may have been committing sexually selected or paternity-influenced infanticide. He - we think it was a male given the brow ridge - could have destroyed the egg because it was not his egg. There is some very lively discussion going on about whether or not this male was last year's father. If he was, he may have destroyed the egg because it wasn't his egg. In this scenario, he arrived at the barn to find his mate had already paired with another male and laid an egg. Since the egg wasn't his egg, he destroyed it. If it wasn't the same male, he may have driven off the original male. Once again, since the egg wasn't his egg, he destroyed it.

In this scenario, paternity was uncertain. The male bird was assuring that all of the offspring produced in the barn would be his. The female could most likely still be fertilized if the egg was destroyed, given that she hadn't laid all of her eggs yet. We haven't seen re-clutching in the presence of eggs, but we have when failed eggs have been removed from the nest. By eating the egg, the male effectively removed it.

Infanticide can also be compelled by resource competition. In this scenario, a parent does not have enough food or nest space for all of its young.  It may kill weaker young or refuse to feed or incubate them. Although Cain and Abel syndrome occurs between offspring instead of adult-to-offspring, it is an example of resource competition that can result in death. As cruel as it seems, the young best able to adapt to limited resources are the ones who will survive.

Finally, we have the last trio: social pathology, gender selection, and reproductive fitness. Social pathology occurs when infanticide occurs for no discernible reason.  Social pathology is a highly maladaptive behavior that doesn't benefit the individual or group. While I have tried to avoid using loaded terms, the closest human analogy would be murder. Eclectus parrots practice infanticide based on sex: that is, mothers kill male offspring. And some birds appear to practice brood reduction to maximize reproductive success, killing particular offspring while leaving others that are presumably more fit. Less mouths are easier to feed. We talk about the role that natural and sexual selection play in driving specialization. Could infanticide also be playing a role?

While this behavior is very difficult for us to understand, it is part of what birds do. The social and emotional lives of birds are complex, and it is my feeling - and I stress feeling here - that birds and humans have some states that are analogous to one another, and others that are not. We shouldn't judge the birds for living their lives - this is not a part of bird life we've seen very often, but it is still a part of bird life. We'll keep watching the barn.

Things that helped me write about this topic:

Friday, April 26, 2013

Red-Tailed Hawks, Nest Greenery, and Ants

First Meal
The hatchling red-tailed hawk at Eaglecrest ate its first meal yesterday afternoon. Like bald eagles, red-tailed hawks eat an extraordinary variety of prey. I thought I detected some fur on baby's first meal, but red-tailed hawks also eat birds, reptiles, insects, fish, and carrion. Eaglecrest's wonderful wildlife resources will provide plenty of food for the rapidly growing hawks.

We also saw the hatchling nibbling at the green leaves lining the bottom and sides of the nest bowl. Watchers know that Stitch and Spot regularly replenish the sprigs of small leaves placed haphazardly around the nest. As pretty as it looks, the hawks aren't bringing in greenery for decoration. The aromatic blue oak leaves may mark active territory, discourage parasitic insects such as fleas, ticks, fly maggots, and lice, or perform both functions at the same time.

Repelling Insects
We know that blue oak leaves release a wide variety of volatile organic compounds. A number of them have been identified as possible insect repellents, including isoprene, an oil that reduces thermal stress and repels insects. At least two mechanisms have been suggested for isoprene's repellent properties:
  • Number one: Isoprene hides host plants and animals by interfering with an insect's ability to smell a host. Parasites can't locate hosts hidden in an isoprene haze.
  • Number two: Isoprene repels insects. As the isoprene outgasses from the freshly cut leaves, it ozidizes to terpene, an insecticide. Many insects actively avoid terpene.
Whatever the mechanism, a number of animal species use greenery in and around their nests, burrows, and dens, including twenty-six members of the order falconiformes. Many of them choose highly aromatic leaves and/or bark, suggesting that appearance or appetite alone do not account for the regular delivery of fresh greenery to their homes. We've watched birds go to amazing lengths to build nests and protect their young. Why wouldn't they try to repel parasites and insects? 

Having said that, the leaves don't appear to work on ants. We periodically witnessed ants on and around the nest on April 25, although they didn't appear to be unduly disturbing the hawks. I'm no ant expert, but they appeared fairly small to me. Ants both migrate and swarm, so while may have been attracted to the nest by prey leavings, they also may have been simply passing through. I haven't been able to find much evidence that ants are especially harmful to birds, outside of a few highly specialized species. Some birds even allow themselves to become covered with ants - a practice known as anting that may be yet another defense against parasites. 

Enjoy watching the wildlife at Eaglecrest!

There is some debate about whether or not birds use greenery to repel or reduce parasites. Although I found the evidence to be pretty compelling, a few writers and researchers listed other possibilities, including that hawks are programmed to snip greenery in much the same way they are programmed to build nests, that hawks like greenery in the nest, and that the greenery is the result of hawks snipping branches away to improve sight lines in the nest.

Things that helped me write about this topic: