Wednesday, April 20, 2016

Eaglet Growth and Development: Week Three

04/13/16: Decorah Nest
04/13/16: Decorah Nest
04/19/16: Decorah Nest
04/19/16: Decorah Nest
D24 is 22 days old today, while D25 turns 21 days old. In the past week, the eaglets' footpads and talons have grown, their feet and legs have yellowed, and their talons have turned almost entirely black. Their mohawks have become more apparent as they shed their white natal down, which disappears from the head last. Almost every time I checked in, the eaglets were either eating or recovering from a meal. Their crops bulged so heavily at times that it was hard to believe they could sit up! They also had a fine buffet to chose from, including trout from the hatchery (look for finer scales and a front pointing mouth with thin lips), sucker (look for rougher scales and a bottom pointing mouth with fleshy lips), rabbit, muskrat, and even a mink.

Eaglets spend roughly 75-80 days in the nest, so we are a little under a third of the way to fledge. Most birds of prey seem to spend roughly the first half of nest life gaining weight and growing structural features like footpads, talons, toes, and beaks. While some structural growth may occur later on, the second half of nest life is dedicated to feathers and wings as feathers replace down and wings lengthen.

This week we were treated to a lot of eating and sleeping, but big changes are on the way! Pinfeathers started growing out late in week three and poop went from little slices to big spatters as the eaglets got better at sitting up, bending over, and shooting poop! What else can we look forward to in the coming week?
  • The eaglets should start standing on their feet. This will change nest exploration and enable them to really get to work on the Poopcasso tree!
  • Natal down mohawks will vanish and dark deck feathers will poke through the eaglets' natal down at an astonishing rate.
  • Still enclosed in their keratin sheaths, eaglet pinfeathers will grow longer. 
  • We may be treated to the beginning of wingercizing sessions! Once the eaglets can stand, they can really begin exploring their wings. 
By the end of the fourth week, the eaglets should be standing well and may be starting to walk and tear their own food. I have no doubt that many of us will be mouse-clicking, shoeing, and blowing to get inquisitive eaglets back into the center of the nest as they widen their explorations and begin broadening their horizons! 

While we've been making guesses at gender, the weight of the two sexes begins to separate as females gain weight faster than males.  Sex takes over from age as a size determinant around 50-60 days. But cameras can be tricky and clutches can have large males and small females or be all one sex, making ID impossible without measurements or a genetic test. We'll have a lot of fun seeing if size conforms to our observations based on what we have seen of beak size, commissure extension, and other traits, and I can hardly wait for food tearing and wingercizing!

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.

Stage 3 - Neurological Coordination. Eagle watchers know how ungainly eaglets can seem! As they grow, they become more adept at controlling beaks, legs, wings, and feet. They 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. We discussed it very briefly in this blog and I'll include links below. 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 legs, feet, and wings are starting to 'light up' this week, leading important behaviors like standing, tearing, and flapping!

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

1 comment:

Robert said...

I have been watching the Decorah North Nest since the cameras were turned on. I watched the Decorah Eagles nest since 2011, including the year that Mom and Dad Decorah decided they needed a new nest. Of course, there were no cameras that year. I have been blessed to be able to watch these raptors as they raise there young. Something is different this year watching the DN Nest. There are no opportunities to learn the way of the bald eagle as there was with the DE nest. That nest had a considerable amount of chat time, with moderators and even actual chatters that knew what they were talking about. There was no chance of ending your watching day confused. Questions were asked and answered then and there. The mods were respected.
Without a way to ask questions or simply read the chat daily through the day, there is no learning experience. People can only watch and come up with their own ideas about what they see. This is where all the negativity seen this year comes from. It will only continue and likely become worse. With no one to guide us, "the Mods", we are left with no choice but to figure out as best we can, what it is that we are seeing. In the beginning, there was a Social Stream without moderators. Not the best way to try and understand what was going on. It was, however better than what we have now. One hour of moderated chat which move so fast that my 79 year old eyes can not keep up with it.
I am not trying to tell you how best to run these eagle cams. I'm just making an observation. Friday evening there was a chatter on making lots of negative comments. If there was regular daily chat probably this would not have happened. The bottom line is the one hour chat in the evening does not allow for any of us to learn about what we are watching. I myself watch several hours every day and evening.
Thanks for your time and I really hope you can see the point I am trying to make. Also, I hope this is in the correct place for someone to see it.
Robert Frisone