Wednesday, October 17, 2018

Who's on N2B? Welcome to the Confusion Couch!

Welcome to the Confusion Couch! Many of our followers are asking "Who is that eagle?" after watching the Decorah and Decorah North nests this week. In Decorah, an adult male eagle that we've been calling DM isn't DM (or Dad - sorry, everyone!). And we can't decide who we're seeing ar Decorah North. Is that Mr. and Mrs. North, or are we seeing somebody else?

Let's start with Decorah. We originally thought that DM came to N2B a couple of days ago, but started to rethink it after taking a closer look. We needed iris patterns and John was able to get some yesterday. We're going to start with head studies...

Decorah Male, FKA UME, June 2018. DM lost feathers during a blackfly strike, which left him pretty tattered looking. He presumably would have grown them in since then.
DM? October 16, 2018. While DM would have regrown feathers lost in the black fly attack, this head study gave us pause. It sure didn't look like DM!
Dad Decorah, February 2018. Rumors quickly began to fly that the October 16 eagle was Dad returning to N2B.

The three head studies offered a tantalizing hint that our October 16th eagle was not DM, but more was needed to prove it. Fortunately, irises are very helpful in ID’ing individual eagles. Like fingerprints, each iris is unique.

DM? Male eagle from October 16, 2018
DM, June 2018
Dad Decorah, February 2018

We are looking at the left side of the eagle’s face in every photo, so we’re comparing left iris to left iris. The irises of all three eagles have distinctly different patterns and markings. The eagle we thought was DM, who we will refer to as UME-2 from now on, has an iris with some patterning around the center and a distinct small blotch at around 3:00. Like UME-2, DM’s eye has some central patterning, but he has two eye spots instead of one, and his eye spots are located at about 5:30 and 7:00. Dad’s eye has less central patterning and more eye spots than either UME-2 or DM. I checked earlier iris surveys and found that Dad’s iris splotches and dots didn’t change much over the years we watched him, which rules out a return. UME-2’s irises are simply too different for him to be Dad.

So why did we think this eagle was DM at first? First and foremost, that’s who we expected to see. DM has been identified recently and has been on territory pretty consistently since he showed up in April. Mom’s response didn’t give us any reason to question the eagle’s identity – a prey chase is often game on and Mom has chased DM around! – and he seemed quite comfortable at the Y and on N2B. We’re reminding ourselves to look closer before ID’ing eagles, especially in a rapidly changing situation like this. Bald eagle mate changeovers are a new thing for us and we’re learning a lot about what that can look like. We’re also wondering if this eagle hasn’t been here a little longer than we thought. Has Mom been perching with UME or DM or some other eagle in the maple tree? At this point, we don’t know.

How about Decorah North? We’re in an active discussion about Mr. and Mrs. North as I write this. We aren’t seeing white pantaloon streaks on the female eagle that is visiting the nest now, but the head and facial features are very similar. Are the white pantaloon feathers really a good marker? I checked in with our eagle panel, who felt that they were pretty reliable given that Mrs. North has had them for the three years we’ve watched her. But no one could say for sure. Both eagles have been seen pretty consistently and they are spending time in familiar spots. However, those spots might be desirable to any eagle, so that’s not really an indicator either. I’ve put myself on the Confusion Couch here, but we will be trying to get some good close-ups for iris and leg scale comparison.

So what’s going to happen next? Is Mom going to bond with a new male this year? Will it be DM or has another male pushed him out? How long will it be until we know? Unfortunately, we have no idea. Until last April, it seemed like Mom and Dad would be together forever. As of this fall, it seemed like Mom and DM might enter into a pair bond. And now we’re throwing our hands up into the air, getting back to eagle time, and waiting for Mom to show us what she’s going to do. Eagles are moving around right now, which means that Mom may have plenty of suitors to choose from and UME-2 may not be the last new male we see at N2B this year. We’ll continue to get eye patterns when we can at both of our nests, we’ll do our best to count the visitors, and we’re looking forward to learning more about this stage of eagle life. Go eagles – and the best of luck to both nests this year.

The takeaway? We don’t always know as much as we think we know and ID takes time and skill…especially in a situation like this. We need to make sure we don’t let our personal stories and ideas about the eagles interfere with our eagle observations – not an easy task when we spend so much time watching and thinking about them! Behavior can help guide observations, but may not be especially helpful given that good perching and nesting spots might appeal to multiple eagles.

A Guide to the Acronyms

  • DM stands for Decorah Male. Formerly known as UME (Unknown Male Eagle), he showed up in mid-April, right after Dad disappeared. 
  • UME-2 stands for Unknown Male Eagle 2. UME-2 has been on site since at least October 15. While we don’t give every eagle we see an ID, UME-2 has been in N2B, perched near N1, and been pursued by Mom. He’s been on site long enough to get an ID. 
  • N2B: N2B stands for Nest Two-Bob. N2, or Nest 2, went down in a storm in 2015. Bob approved the starter nest plan but died before it could be completed. We named the nest in his honor. 
  • N1: N1 is the second nest on this territory. It was over in a tree across Siewers Spring Road, but has mostly disintegrated since the eagles left it in 2012.

Tuesday, August 14, 2018

What's on the menu at the Decorah North Nest?

Kike collected prey remains from the Decorah North nest when we were working on cameras in the fall of 2017. Since my family was tired of animal parts in the garage and 2018's fall camera work is just around the corner, I decided it was time to get them identified!

The photo below shows all of the remains that Kike recovered from the nest. In all, he found 23 white-tailed deer remains (4 partial skulls, 18 leg bones, including four with the hooves still hatched, and one sacrum that measured 3-7/8" wide by 7.5" long), three wild turkey remains (legs with the claws still attached), one opossum skull, one raccoon skull, an unknown set of wings, a dry corncob, 4 unknown vertebrae, 1 unknown skull fragment, and some unknown mammalian leg bones. We also found some miscellaneous clods of fur that looked like white-tailed deer fur given the color, texture, and size of the fur piles. These were not included in our count.

I was really surprised that we didn't find more fish remains! Sherri Elliott provided this list of menu items from the 2017 North Nest season:

Feathered (19)
  • Birds (6)
  • Chicken and parts (4)
  • Coot (2)
  • Duck (1)
  • Gosling (2)
  • Grouse or Pheasant (3)
  • Turkey or Goose (1)
Finned (246)

  • Trout (144)
  • Sucker (44)
  • Fish pieces (58)
Furred (47)
  • Deer – Heads (4) 
  • Legs or sections (12) 
  • Groundhog or Muskrat (2)
  • Oppossum (2)
  • Rabbit (8)
  • Raccoon and pieces (11)
  • Squirrel (6)
  • Field Mice or Voles (4)
Reptiles (2)

  • Turtles (2)

Miscellaneous (125)
  • Cow Placenta (37)
  • Mystery Meat or Unidentified Food Objects (48)
  • Animal legs/feet (4)
  • Pink/Red Innards (24)
  • Bony Meat (12)
What we saw come into the nest was in line with our expectations about what eagles eat overall.  As we've seen in our other nests, the North Eagles have a preference for fresh fish but will happily eat other foods, especially if those foods fall into the low risk/high reward category - think cow placenta, which takes very little energy expenditure or risk to get when cows are calving near your nest tree. However, if we had been relying on nest remains to determine eagle diet, we would have had a very distorted view of their food web. The prey remains we find in a nest might not adequately reflect what the eagles are eating, especially if they are eating foods that don't leave prey remains behind (placenta, innards), decompose quickly or fall into the nest (small or previously butchered prey), or are eaten by nest visitors like mice, squirrels, and other birds.

Having said that, I was surprised by all of the white-tailed deer. We've been asked about it several times. Were the deer killed by a combine? Were the deer road-killed? Are the eagles preying on live fawn deer? What's up with all the deer?

To solve the puzzle, we have to start with the season. Mr. and Mrs. North were bringing in fawn deer between April and mid-May. Combines aren't used for discing, planting, or early cultivation, which rules out combine-killed deer. There aren't a lot of hay fields in the area and it is also too early for haying. How about road-kill? We can't rule it out entirely, but the area doesn't have many roads or much traffic, and the whole legs and sacrum were not smashed, broken, or splintered, something I would expect to see in road-killed deer. Many of the deer parts were also fairly well-developed, with small black hooves and/or bits of fur still clinging to them, which rules out aborted fetal deer.

Were Mr. and Mrs. North predating fawn deer? We used to assume that any deer brought into the nest were scavenged, but bald eagles have been observed predating fawn deer. In 2011, naturalists documented predation of a radio-collared white-tailed fawn in Menominee County, MI. In 2016, biologist Sophie Gilbert documented bald eagle predation of Sitka Black-tailed fawns. In 2017, a landowner in northeastern Wisconsin witnessed an eagle attack and kill a swimming fawn. Once the fawn was dead, the eagle dragged it to land and began feeding. In other words, it is possible that Mr. and Mrs. North were preying on fawn deer, not simply finding them dead.

The documented research on eagle/fawn deer predation tends to indicate that eagles don't commonly predate deer, so why are Mr. and Mrs. North bringing so many deer to the nest? While four or five deer (based on skull count, leg count, and observation) isn't a whole lot of deer either population or percentage-wise, it is more deer than were documented in Gilbert's study or the study done in Michigan. A few thoughts:
  • Eagles know their territories and their prey. It wouldn't take Mr. and Mrs. North long to learn that fawn deer are vulnerable to predation, especially during the first three to four weeks of life. While the Norths prefer fish over everything else, they would be happy to take an animal with a lot of reward for very little risk. 
  • There are a lot of deer in the valley of the Norths. The river, grasslands, and upland forests are surrounded by row-cropped corn and beans. This concentrates deer (and many other animals) along the river's corridor. Predated or scavenged, the presence of deer in the North's diet might be a function of the sheer numbers of deer in the valley. 
  • The Norths have an excellent territory in which to find and predate fawn deer. Their forests are relatively open, reducing the amount of cover for fawns to shelter in. Deer often cross the broad, open valley for water and forage, putting young fawns at risk once they begin traveling with their mothers. 
What did we learn? The North nest prey remains did not accurately reflect the North's overall diet, but still yielded some interesting surprises! Given the scarcity of data on eagles predating fawn deer, we'll be looking into this issue more deeply. I'm also curious about the lack of opercular bones given all the trout and suckers that were brought into the nest. We found them in the Fort St. Vrain nest. Why aren't they here?

Did you know? Bonus Skull!
Teeth are my best friend when it comes to skull identification. The skull below is upside down. Our mystery animal has some pretty unique teeth. Its combination of sharp front teeth and molars for grinding mark it as an omnivore. How many front teeth does it have past its sharp canines? It's hard to see here, but I counted ten. This marks it as an opossum! Opossums have 50 teeth total - more than any other North American land mammal!


Tuesday, August 07, 2018

Birds Threatened By Proposed Rollback Of Endangered Species Act Protections

Imagine a world where there were no bald eagles or peregrine falcons. By the late 1960's, rampant use of the pesticide DDT, habitat loss, and persecution made extinction seem very likely. The Endangered Species Act (ESA), signed into law by President Nixon in 1973, was an important part of bald eagle and peregrine falcon recovery. It:
  • Levied serious legal penalties for killing threatened and endangered species;
  • Mandated the preservation of habitat critical to a listed species' survival, and;
  • Decreed that federal agencies prevent their actions from jeopardizing the existence of threatened and endangered species. 
Despite overwhelming public support for the Act, the U.S. Department of the Interior is currently proposing to roll back endangered and threatened species protections in three critical areas. Their changes will:
  • Roll back habitat protection for endangered and threatened species; 
  • Reduce protections for and allow take of threatened species, and;
  • Weaken the role that biological assessment and science play in listing decisions.
Federal rule changes require a period of public input, which in this case ends on September 24th. If any of you would like to comment, we've put together a breakdown of the proposed changes, what each change actually means when stripped of its bureaucratic language, and links to comment. The changes break down like this...

Critical Area I: Rolling back habitat protection for endangered and threatened species
Revision of the Regulations for Listing Species and Designating Critical Habitat. This proposed rule change will make it harder to designate critical habitat: the land and waters that endangered and threatened species need to survive. It will also make it easier to eliminate existing critical habitat, opening previously protected land to commercial and recreational use.
  • What it says: "We propose to revise section 424.12(a)(1) to set forth a non-exhaustive list of circumstances in which the Services may find it is not prudent to designate critical habitat as contemplated in section 4(a)(3)(A) of the Act. Under the clarifications that we propose in this revision, the Services would have the authority but would not be required to find that designation would not be prudent in the enumerated circumstances."
  • What it means: 4(a)(3)(A) requires the Service to designate critical habitat when it makes an endangered or threatened listing; i.e., when a species is listed, its habitat must also be listed. The proposed rule change would allow the Service to exempt habitat from the listing.
  • Why it's important: For endangered species, critical habitat is the key to survival. A study by the Center for Biological Diversity found that plants and animals with federally protected habitat are more than twice as likely to be moving toward recovery than species without it. Migratory species like birds are especially vulnerable to habitat destruction because they tend to inhabit more than one natural habitat. This seemingly innocuous proposal eliminates one of the most important tools we have to protect and rebuild species in danger of going extinct. If species don't have a place to live, migrate, feed, and breed, listing means little to nothing.
What you can do: Comment on this change by pressing the blue "Comment now" button at the upper right side of this page:

The devil in the details: The federal government seeks feedback on whether it should consider modifying the definitions of “geographical area occupied by the species” or “physical or biological features” in Section 424.02. The geographical area is currently defined as an area that may generally be delineated around species' occurrences. This may include those areas used throughout all or part of the species' life cycle, even if not used on a regular basis (e.g., migratory corridors, seasonal habitats, and habitats used periodically, but not solely by vagrant individuals). The physical or biological features are the features that support the life-history needs of the species, including but not limited to, water characteristics, soil type, geological features, sites, prey, vegetation, symbiotic species, or other features - including critical ephemeral locations like migratory feeding, wintering, or summering grounds. Changing these definitions could have a significant negative impact on habitat conservation.

Critical Area II: Rolling back legal protection for threatened wildlife and plants

Revision of the Regulations for Prohibitions to Threatened Wildlife and Plants. This proposed rule change will reduce legal protection for wildlife and plants listed as threatened.
  • What it says: "We, the U.S. Fish and Wildlife Service, propose to revise our regulations extending most of the prohibitions for activities involving endangered species to threatened species. For species already listed as a threatened species, the proposed regulations would not alter the applicable prohibitions. The proposed regulations would require the Service, pursuant to section 4(d) of the Endangered Species Act, to determine what, if any, protective regulations are appropriate for species that the Service in the future determines to be threatened."
  • What it means: "Take protection" was extended to threatened species in 1978. Like endangered species, threatened species can't be harassed, harmed, pursued, hunted, shot, wounded, killed, trapped, captured, or collected. It provides safeguards to species that are in need of support, but allows some activities to be exempted if the Service finds it appropriate. The proposed rule change would remove these protections for species listed as threatened.
  • Why it's important: Section 4(d) provides legal protection and resources to threatened or dwindling species while rewarding collaborative conservation efforts to keep species like the Gunnison Sage Grouse off the endangered species list. Rolling back these protections will allow threatened wildlife and plants to be subject to "take". It will also remove incentives for collaboration, making it more difficult and costly to reverse population declines. The Section 4(d) rule was designed to create fewer endangered species by providing incentives to protect and rebuild threatened species. Rolling it back will cause population declines among wildlife and plants already struggling to hold on, creating more endangered species.
What you can do:  Comment on this change by pressing the blue "Comment now" button at the upper right side of this page:

The devil in the details: The federal government seeks specific feedback about replacing blanket 4(d) protections with special rules for each species listed as threatened. It also seeks feedback regarding a timeframe for finalizing any rules, after which the rule would be dropped and the process restarted before any decision could be made. Replacing blanket protections with special protections and drop rules will significantly reduce protections for threatened species, especially given the dwindling resources allocated to the Fish and Wildlife Service.

Critical Area III: Weakening the role that biological assessment and science play in listing decisions

Revision of Regulations for Interagency Cooperation. This proposed rule change will weaken the role that biological evidence and science play in listing decisions.

  • What it says: "We, FWS and NMFS (collectively referred to as the “Services” or “we”), propose to amend portions of our regulations that implement section 7 of the Endangered Species Act of 1973, as amended. The Services are proposing these changes to improve and clarify the interagency consultation processes and make them more efficient and consistent."
  • What it means: The Endangered Species Act currently directs all Federal agencies to work to conserve endangered and threatened species and to use their authorities to further the purposes of the Act. The proposed changes to Section 7 weaken the requirement that Federal agencies consult with the U.S. Fish and Wildlife Service when any action an agency carries out, funds, or authorizes may affect a listed endangered or threatened species.
  • Why it's important: When a Federal agency determines that its action is likely to adversely affect a listed species, the agency submits a request for formal consultation to the Fish and Wildlife Service. Formal consultation includes sharing information about the project and species likely to be affected by the action. Once formal consultation is done, the Service prepares a biological opinion on whether the proposed activity will jeopardize the continued existence of a listed species. The Section 7 Rule mandates consultation and produces listing decisions based on the best available biological science. Rolling it back will reduce the role that science-based evidence plays in making listing decisions and minimize the role of the US Fish and Wildlife Service in conserving America's wildlife and plants for the public good.

What you can do:  Comment on this change by pressing the blue "Comment now" button at the upper right side of this page:

The devil in the details: Note that the federal government is seeking comment on the extent to which the changes outlined in this proposed rule will affect timeframes and resources needed to conduct consultation and (2) anticipated cost savings resulting from the changes. They are also seeking comment on the merit, authority, and means for the Services to conduct a single consultation, resulting in a single biological opinion, for Federal agency actions affecting species that are under the jurisdiction of both FWS and NMFS. FWS has a higher standard.

According to the proposed rule changes, the federal government seeks only to make things more efficient and streamlined. Their concentration on technical definitions, bureaucratic language, and efficient timeframes conceals their true intent - to drastically roll back protections for endangered and threatened animals and plants and the habitat they live, feed, breed in, and move through. If I didn't find it all so appalling, I might be awed by the sheer nefariousness of this death by a thousand cuts. Follow the comment links earlier in this blog to speak up for America's wildlife and wildlands.

Opponents of the Endangered Species Act sometimes argue that the law hasn't been successful, but according to a 2016 report published by The American Bird Conservancy, seventy-eight percent of mainland birds listed as Threatened or Endangered under the ESA have populations that are now stable, increasing, or have recovered enough to be delisted. That sounds an awful lot like success to me.

Why do I care? I had the privilege of visiting Chicago's Field Museum during a peregrine conference five years ago. Attendees were given a behind-the-scenes tour of the museum, including a look at their vast bird collection - lovingly preserved corpses of birds kept for study and remembrance. It was there that I got my only look at the Carolina parakeet and the Ivory-billed woodpecker. Gone forever from life, the two species now exist only as study skins in museums. Had the United States not banned DDT and passed the Endangered Species Act, it is highly likely that peregrine falcons, bald eagles, and many other animals would have joined them, existing only as rumors, museum specimens and curiosities on film. However cherished their memories or lovingly preserved their corpses, they too would be gone, dead, extinct, lost. Forever. I care because I've come to love them, and because I also believe that their survival is our own. This land is our land. We need to care for it and respect it

Monday, April 23, 2018

Questions about N2B: Dad, UME, Mom, and the eaglets

We're getting a lot of questions about the situation in Decorah. What happened to Dad? Will Mom abandon the eaglets? Did the unknown male eagle attack Dad or drive him away? Are the eaglets being fed? Is Mom feeding herself? We put together a timeline and answers to the most asked questions. Keep in mind that, while researchers have studied bald eagles for years, this level of observation became possible only very recently and there is much that we are seeing for the first time.

Timeline of events
  • 4/18/18: A serious snowstorm follows right on the heels of a three-day weekend storm. Mom and Dad spend the day caring for the eaglets, at times feeding and brooding them together in the nest. Dad is last seen on the nest around 7:30 PM. Mom broods overnight. We have been reviewing the footage to look and listen for anything unusual, but the process is time-consuming. We will let everyone know if we do.
  • 4/19/18: A bright, sunny day follows the storm. We are a little concerned when Dad doesn't replace Mom for his morning shift, but think that he might be resting up from the intense flurry of activity following two large storms. As the day wears on without Dad, we become more concerned and begin making plans to go look for him. We see another eagle. Is that Dad? We send an on-the-ground observer, who tells us that Dad is there. However, Dad doesn't show up to feed the eaglets or give Mom a break. 
  • 4/20/18: We enter a second day without Dad. We are increasingly worried that something has gone wrong. Mom continues to care for the eaglets, who are stuffed to the point of bursting with nestovers and fresh-caught fish. However, she clearly knows that Dad is gone and at times seems very wary about activity near the nest. She peal calls throughout the day with no response. Our camera operators catch several glimpses of another eagle in the area. We determine it is a male eagle and designate him UME, or unidentified male eagle. Could that be Dad? If it isn't, why is Mom tolerating him so close to the nest? He spends part of the day perched above it and Mom at one point perches near him. If it is, why isn't he giving Mom a break, bringing in prey, responding to her peal calls, and harassing an osprey that has perched by the pond? Why does she seem so wary of his presence? Unfortunately, UME never comes close enough for a look at his iris, molt pattern, or foot scales. John launches a search of the hatchery and nearby areas with some friends, but doesn't find anything. Despite yesterday's observation, we become increasingly convinced (based on behavior and photographs) that Dad isn't here. After a consultation with our eagle experts, we announce that UME is not Dad.
  • 4/21/18: John coordinates a search from the hatchery. 20 volunteers and a drone team from the Decorah Fire Department look for Dad. They search roadways around the hatchery, the bike trail, the stream, the area around N1, the hatchery grounds, hatchery buildings, and power poles and lines to the east. We don't find any sign of Dad. Meanwhile, Mom continues to feed the eaglets and we see UME fly on to the Skywalk and stay for about five minutes. Mom is agitated by the intrusion and remains wary of UME, although her peal calling has largely stopped. 
  • 4/22/18: Dad is still absent, another search doesn't turn up anything, and Mom is still wary of UME (who is still hanging around and does a fly through at one point). She feeds the eaglets throughout the day. While we worry, they have bulging crops and are developing on track: eating, sleeping, pooping, bonking, playing house, wingercizing, exploring their clown-clomping feet, and starting to grow pinfeathers. 
Your questions
  • QQ: Could UME have driven Dad away? Or did Dad leave because he was tired of caring or could no longer care for the eaglets after two big storms?
    We talked with our eagle experts about the likelihood of both questions. It isn't unknown for new eagles to drive away territorial eagles, although we haven't seen displacement during the nesting season at any of our nests. We don't have any documentation of an adult eagle, male or female, simply deserting young, and Dad was caring for the eaglets up until the time he disappeared. Put simply, we don't believe that Dad voluntarily deserted the nest but we don't know where he is or whether UME had anything to do with his disappearance. After several days of terrible migration weather, birds finally got a break and were busy heading north. UME could have displaced Dad, or he may have been migrating through the area when Dad disappeared. Since there was no response to his tentative exploration of the area around the nest, he might have decided to stay and get a little closer. 
  • QQ: What could have happened to Dad? 
    Our search was structured along the following possibilities: UME injured Dad in a fight (we searched around the nest with binoculars and checked the trail, stream, fields, and area around N1). Dad was hit by a car while eating or getting roadkill (we searched roadways and ditches). Dad was electrocuted on or collided with a powerline (we searched the base of poles and along powerlines). Dad got caught in a building (we searched hatchery buildings). We covered a lot of area with 20 volunteers and a Decorah Fire Department drone, but didn't find Dad. We still don't know what happened to him. 
  • QQ: Is UME a threat to the eaglets?
    This is a tough question. Anecdotes and scientific literature both contain examples of new adults killing eaglets and caring for eaglets. We are hopeful that he won't, given that he hasn't behaved in an aggressive way towards the eaglets or Mom. We're waiting to see if he brings Mom any food or courts her. 
  • QQ: Are you going to pull the eaglets from the nest? 
    We are not.  From a human perspective, we would be caring for the eaglets by keeping them safe from hunger and predators. But from Mom's perspective, we would be invading and killing her eaglets. Mom is far more capable of caring for her eaglets than we are, and we have no plans to take her young from her.  
  • QQ: So Mom can feed the eaglets by herself? 
    Mom has fed the eaglets to bursting multiple times every day since Dad disappeared. Between the hatchery and the stream, she is more than capable of keeping them fed. 
  • QQ: I saw that Mom was attacked by a bird. Was that an eagle? 
    Mom was being swooped by crows earlier today. We've also seen starlings and nuthatches steal nesting material and search for food. All of this is completely normal behavior and has nothing to do with Dad being gone. 
  • QQ: Mom seems really wary and watchful. Why?
    Mom is probably responding to UME, who as of this post on April 23rd was still in the area. While he hasn't treated her aggressively, he still isn't her mate and she is usually very wary when he comes near the nest. We've only seen one exception, which happened on Friday, April 20, when she perched near him.
  • QQ: Could this be Mom and Dad's offspring from another year? 
    While it could be, we have no way of knowing one way or another.
  • QQ: How old was Dad?
    We don't know, but believe him to be at least 21 years old based on his plumage and when we first started watching him.. Is it possible that he could have been less cold-tolerant because of age? We're asking our team on that, but we don't know at this point. 
Thank you for all of your care and kind comments. We know this is hard on everyone. We promise to keep you all posted. 

Friday, April 13, 2018

Eaglet Growth and Development, Week Two

It is April 13 as I write this, and our eaglets are growing rapidly! In Decorah, D29 is twelve days old, D30 is eleven days old, and D31 is nine days old.

Left to right: D30, D29, D31
In their second week of development, the eaglets will gain roughly two pounds between their 7th and 14th day of life. They will experience rapid growth in features like beaks, culmens, and footpads, start replacing their white natal down with thicker grey thermal down, and begin exploring the nest. Although they aren't yet standing on their toes, they are able to sit up - way up! - for feeding and shuffle around on their metatarsi. Their eyes are wide open and fit more comfortably in their eyesockets, features like brow ridges are beginning to appear, and their legs and footpads are yellow, not pink. Gary Bortolotti wrote that bald eagles might gain more weight per day than any other north American bird, although the majority of their weight gain occurs within the first 30-40 days. This rapid weight growth is fueled by their nutrient-rich diet of meat. Over the past week or so, we watched the eaglets chow down on fish, rabbit, squirrel, ground squirrel, coot, groundhog, and unidentified birds. D29 became proficient enough at shooting poop to christen the Poopcasso tree on April 9th, although it was quickly joined by its siblings on April 11th and 12th. While babylet battling hasn't entirely subsided, it has become less intense as pecking orders are established and eaglet crops are repeatedly stuffed until they look ready to burst! The eaglets are alternately hitting, submitting, and quitting to cuddle in the nest cup, grow, and wait for more food to arrive. We haven't gotten to see much of them given the cold, but D29 did finally escape the nest cup during warmer weather Wednesday!

So what did we see in the nest this week?

April 8: Eaglet explorers. Despite the cold weather, the eaglets are busy popping out from under Mom and Dad and starting to nibble at nest materials, exploring  the world with their sensitive beaks and tongues.

April 9: Preening! When birds preen, they remove dust, dirt and parasites from their feathers and align each feather in its optimum position. D29's exploratory downy nibbles today marked an important first step on the road to feather care!
April 10: Thermal down begins to emerge! A hatchling eaglet's fuzzy white natal down doesn't assist thermoregulation, aka controlling one's temperature. Denser thermal down provides more insulation and helps nestling eaglets keep their body temperatures at a relatively constant 105'ish degrees. 

April 11: Eaglet escapee! D29 took its first sojourn out of the egg cup today! At ten days of age, D29 weighs between about 2 and 2.5 pounds. It can't stand on its feet, but it can sit upfor feeding and shuffle around on its metatarsi. Its feet and toes are yellow, but its tiny talons are still clear.

April 12: Cropzillas! D29 has just gorged itself on more food than it can stomach! It will store the food in its crop until it is ready to transfer it to its stomach for digestion. This mini 'pantry' helps assure that the rapidly growing eaglets get the nutrients and calories they need, when they need them.

Painting the Poopcasso tree! On the morning of April 9th, the eaglets weren't quite shooting poop as far as the Poopcasso tree. D29 christened it that day, and all of the eaglets were hitting it by the 13th!
In the week to come, we can expect (continued) rapid growth in footpads, talons, and legs. Beak growth will rapidly slow as the eaglets' beaks approach adult size and we may see dark juvenile feathers start to sprout from their grey down. Overall weight and height gain will continue, most likely reaching their steepest curves some time this week. By the end of their second week of life, our little bobbleheads at Decorah will be almost a foot tall! Enjoy eaglet earholes and egg teeth while you still can - their earholes will soon be covered by down and their egg teeth are wearing away.

The general stages of eagle development are:
  • Stage 1 - Structural growth. In their first thirty-five to forty days of life, eagles grow very rapidly, gaining weight and building bones, muscles, tissue, and features like tarsi, footpads, toes, and claws. This phase of development slows down about halfway through an eaglet's time in the nest, even though individual features might continue some level of growth.
  • Stage 2 - Feather and flight-related growth. Eagles grow four sets of feathers - natal down inside the egg, thermal down, juvenile feathers, and adult feathers. Thermal down starts growing at about ten days, juvenile deck feathers at about 20-23 days and juvenile flight feathers at about 27 days, but feather growth doesn't overtake structural growth until thirty-five to forty days after hatch. Flight muscles also begin growing as eaglets wingercize, flap, hover, and eventually branch and fledge.
Neurological coordination occurs throughout an eaglet's time in the nest. During week two, their eyesight and basic coordination skills are improving as they grab food from Mom and Dad, sit up tall for feedings, shuffle around on their tarsi, and explore the world with their sensitive beaks. As they grow, they will become more adept at controlling beaks, legs, wings, and feet. They will learn to stand on their own feet, tear food, self-feed, and flap their wings, going from cute but clumsy clown clompers to graceful young eaglets poised at the edge of fledge.
I'm not sure how familiar many of you are with the cortical homunculus, an image-based tool that maps tactility. While useful and extremely cool, most cortical homunculii are static - that is, they reflect just one phase (usually adult) of an organism's life. But an eaglet's cortical homunculus will differ from an adult's as body parts and associated skills are gained and neural pathways developed. Our eaglets' brains and bodies are rapidly growing and changing as they gain the skills they need for life outside the egg! I'd tend to think that visual acuity and eaglet beak and tongue sensitivity  suddenly 'lit up' this week, leading changes in coordination as the eaglets began sitting up, grabbing food, moving around, and preening and nibbling at things.

Things that helped me write this blog, with a few considerations:

Tuesday, April 10, 2018

Bald eagle tongues and beaks!

This blog was inspired by RRP Director John Howe, who was reviewing footage of Mom and Dad feeding eaglets and was delighted by the dexterity of their beaks and tongues. I had never blogged about that topic and it was very fun to learn about just how specialized some beaks and tongues are!

We know that bird beaks are specialized for feeding. Birds of prey have strong, curved beaks with sharp edges to help them tear meat. Falcons specialize even further, adding a tomial tooth to help them kill prey. Dabbling ducks have tiny, comb-like structures on their beaks to strain small animals, insects and plants from water and mud, while piscivorous ducks have saw-like structures to help them hold on to struggling fish. But what about bird tongues or, more specifically, bald eagle tongues? Are they specialized as well?

Let's start by taking a look at Mom and Dad's tongues!
Dad's Tongue

Mom's Tongue

At first glance, bald eagle tongues look somewhat similar to ours. They are pinkish, relatively narrow, fit nicely between the sharp ridges of their beaks, and are flexible. They are short enough that eagles can't easily bite their tongues, although they can stick them out. Unlike us, bald eagles have two barbs, or rear-directed papillae, to help lift and pull food items to the back of their long mouths: a relatively common feature in bird tongues.

Although birds of prey don't have specialized tongues, their tongues (and beaks) are packed with mechanoreceptors that respond to pressure, distortion (think of an eagle stretching its tongue or biting into bone), temperature, texture, and vibration. Merkel cells are sensitive to very fine changes in touch, pressure, and temperature. These tonic cells keep providing information to tell Mom and Dad exactly where their beaks and tongues are and what they are doing. Phasic Herbst and Ruffini cells sound an alarm to let Mom and Dad know that something has just happened. Herbst cells are sensitive to vibration, pressure changes (I grabbed or dropped an object), and texture changes. Ruffini cells are sensitive to stretching, distortion, and temperature (I just bumped something warm and hard - must be an eaglet's beak and mouth).

These sensors aren't evenly distributed throughout a bird's beak. While I couldn't find any studies on birds of prey, studies have been done on quail and ducks. Sensory cells in a quail's beak are distributed like this:

Cadual BeakMiddle BeakCranial BeakBeak TipCell Type

Bald eagles have considerably different diets and lifestyles than quail, but both ducks and quail concentrate sensors in the cranial areas of their beaks (think of a falcon's tomial tooth or Mom and Dad's tomial ridge). Once a bird has allowed something past the tip of its beak, it has a lot of decisions to make about how to respond to it and what to do with it. Given that quail and ducks are preccocial omnivores and bald eagles are altricial carnivores, I would love to see a study on bald eagle beaks.

Thanks to their beak blinders, bald eagles have a blind spot directly in front of them, which means they can't always see their young during feeding. So how do they select food, find the eaglets, and get food into their mouths? Immediate and ongoing sensory feedback helps parents and young align beaks, and tells new hatchlings to open their mouths wide for food delivery! Once both beaks are in the correct position, Mom or Dad use their sensitive, flexible tongues to carefully push food into the eaglet's waiting mouth. Changes in pressure, temperature, and texture help the eagles change course in mid-delivery, detect dropped food, find eaglets, and pull back as needed. Mom and Dad also use their tongues and beaks to detect and avoid feeding young hatchlings chunks of bone, large pieces of fur, or sharp fins that could cause them to choke.

How do Mom and Dad manipulate food so well? Check out the top photo, which shows a side view of Dad's tongue. We can clearly see that its fleshy tip rests on a muscular stalk. As described in Laura Erickson's excellent blog on bird tongues, this stalk controls Dad's tongue to manipulate food items. Dad can stretch and tip his tongue forward to feed eaglets, pull and tip it backwards to move food into his mouth, or move his tongue to one side or another as needed. His flexible two-stage tongue and rear-directed papillae give him incredible control, and the sensory cells packed into the tip of his beak and tongue provide the feedback he needs to feed eaglets...even when he can't quite see where they are. Annoyed with Mom or Dad over dropped food or missed beak-loading opportunities? Imagine trying to feed eaglets using your just tongue and nose! The video below shows just how delicate they are when it comes to feeding hatchlings.

Did you know? 
Bird banders can use the color of a bird's mouth and tongue to help age birds. Younger birds may have spots or bands to help parents with food targeting. Colored tongues in some adult birds can aid mating displays and/or signal a warning to other birds.

Understanding a species' behavior and diet helps us understand how its tongue and mouth evolved. Check out Laura Erickson's blog More About Bird Tongues Than A Normal Person Would Want To Know for a great look and description of some bird tongues! You know you want to learn more!

Things that helped me learn and write about this topic

Friday, March 23, 2018

The Broken Egg at the Decorah North Nest

We asked our panel of eagle experts about the broken egg at the Decorah North nest. Could egg viability be determined from the video? Did they have any ideas about egg breakage? Was Mrs. North likely to produce more eggs?

In general, the panel believed that the egg’s viability couldn’t be determined from the video, although two of them commented that a darker patch in the draining egg fluid could have been an embryo. At 19 days old, an embryo would still have been quite small and not especially easy to see given the circumstances. Since we couldn’t come to a definite conclusion, our answer is “No” – we don’t know whether the egg was viable or not. We have some information about embryonic developmental stages here:

So why did the egg break? Female eagles lay down calcium in their shell gland/uterus, and their large eggs take a lot of calcium. Was she not able to lay down enough calcium to protect her egg from breaking, and if so, why? She may not have had enough calcium available during that stage of egg formation, or something else could be going on with her reproductive system. One member of the panel asked about her age. Female bald eagles and peregrine falcons can experience reduced fertility as they age. They might lay fewer eggs, strangely colored eggs, oddly shaped eggs, ‘smooshy’ eggs, thinly-shelled eggs, or infertile eggs that never hatch. It’s too early to know whether that’s the case, but we will be watching to see if any of those things happen moving forward.

Was she poisoned again? We saw no sign that she was poisoned this year, and the poison from two years ago would not affect her shell deposition now.

Is Mrs. North likely to produce more eggs? The answers were mixed. If she does, it should happen around March 30, or about 14 days after she lost the first one. Other birds of prey, including gyrfalcons and barn owls, take 14 days to recycle after losing a clutch. I really went back and forth about this (19 days is a long time to incubate an egg!) but the answer gave me some hope, especially given that Mr. and Mrs. North are still copulating. We’re crossing our talons, hoping for the best, and keeping a very sharp eye on Mrs. North!