It's amazing the difference a day makes - they hatched about 36 hours apart, but the differences in size is huge.
The wind is out today big time, I'm nearly getting seasick watching the tree away to and fro, how must they feel
Very interesting watching the feeding - at the first sign of indifference, the parent covers them back up again. The "fighting" between the two chick is hilarious, they quite easily get toppled over.
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!