We have your Monday morning North milestones and movie marathon! The Decorah North eaglets turn 16 and 15 days old today. While the wet, chilly weather put a damper on nestploration in their second week, we thrilled to several milestones, including a first fish tail (DN15), a first pellet cast (after the fish tail), emerging thermal down, and huge cropzillas on both eaglets!
DN16 left, DN15 right. See the difference in size and natal development? 34 hours makes a big difference when you have such a rapid growth curve.
Pellet Casting
Why is pellet casting a big deal? Eagle parents feed their hatchlings ‘baby food’ – tiny morsels of pure meat that can be easily swallowed and are completely digestible. But as eaglets get stronger, more coordinated, and more demanding, meals start to include non-digestible bits: the scales and fins on a hastily-gulped fish tail, for example. Once DN15 swallowed a fish tail, we knew that a pellet would follow close behind!
Thermal Down
DN15 left, DN16 right. See DN16’s tiny earhole? Enjoy it now – but also look for the flat feathers that cover adult ears. We’re not sure if they aid hearing by channeling sound, baffling wind, or both. Also: look at those rapidly growing clown clompers!
If you’ve followed the Decorah North Eagles for more than a year, you know that this spring has been late and cold! Fortunately, both eaglets are growing nice ‘coats’ of dense, wooly thermal down. Natal down feathers – the adorable fluffy feathers that eaglets hatch with – are terrible at locking in heat. But their new grey flannel pajamas trap heat and are better at repelling water, which means that we should see a lot more eaglet exploration next week!
Want to learn more about natal down, thermal down, and flight feathers? We have a blog for that! https://www.raptorresource.org/2019/05/01/from-bobble-heads-to-eaglets-natal-down-thermal-down-and-flight-feathers.
Return of the Cropzillas!
Have the eaglets eaten? Look for a bulging cropzilla or snack pack. If you see one, the eaglet has eaten!
Watchers sometimes worry whether eaglets are getting enough to eat, especially when older siblings bonk down younger siblings. Bald eagles have one of the fastest growth rates of North American birds, which means that a hatch difference of as little as 34 hours can mean a huge difference in size and ability. We cross our talons and trust the eagles, but we also look at their crops. Even if we miss watching a feeding, swollen crops let us know that the eaglets are getting plenty of food! Check out these cropzillas!
Mr. North and DNF are also changing. As their gonads begin shrinking, they decrease courtship and pair bonding behaviors. As prolactin ebbs, their metabolisms speed up, they become more physically active, and they probably become hungrier. But they still take time for a little afternoon delight!
Bald eagles are so fascinating! An interesting thing to me: they go through what I think of as a human reproductive lifecycle every year. We watch gonadal recrudescence, new love, babies, children, empty nesting, and gonadal senescence. For us, that’s a lifetime. For them, that’s a year. What’s up with our eagle Moms? Their hormonal regime is changing: https://www.raptorresource.org/2019/05/09/what-is-up-with-our-eagle-moms/.
If you made it this far, thank you so much for watching, sharing, learning, and especially for caring. Let’s keep working to make a difference for all of the wildlife we love.
Sibling love! DN15 (right) gives DN16 an adorable wing hug
The Raptor Resource Project