You may know that owls regurgitate pellets which consist of undigestible parts of the prey such as fur, feathers and, since they do not have strong enough stomach acid to dissolve them. the pellets contain bones. I have seen owl pellets with almost intact skeletons of mice.
Bald Eagles have very strong stomach acid and generally digest most of the bones they eat. Like most birds, eagles' gizzards have strong muscles which compress and grind up the food. There will still be some parts of their prey which will not be digested, so they too expel pellets.
I once saw one of the Pembroke Pines eagles regurgitate a large amount of sticky white stuff in a long string. I wondered if it had eaten something bad and its stomach rejected it. Indeed, throwing up fluids may sometimes be a sign of illness or happen after a serious injury. Eagles with lead poisoning may vomit. In this case, the eagle seemed go on about as usual after the event.
Philip Martin and another observer at the nest earlier yesterday (JAN 3) reported this observation, in Phil's words:
I do have a little concern. As we discussed, we both saw the female throwing up. On Monday, I saw her throw up what appeared to look like poop. That she threw up this red gel type stuff (I have a photo of you would like). I sent the photo to a wildlife vet friend of mine and she couldn’t identify it. She speculated that it may be undigested fish or frog guts.
Photos are property of Philip Martin and are published with his permission. Although some may consider this "gross," they illustrate an interesting aspect of eagle behavior as well as the importance of keeping eyes on the eagles and caring about their welfare. Like Phil, I hope this is not a sign of illness or injury. Perhaps it is some harmless foreign substance which was indigestible:
Later in the day, Phil wrote:
I spent several hours this morning out at the nest, observing the female. She did not regurgitate the entire time I was there. Attached is a photo I took.