Eaglet DN3 died sometime yesterday. Why did DN3 die? While it didn't get nearly as much food as its larger siblings, it was still shooting poop yesterday, indicating that it had enough in its system to be pooping and excreting urates normally. However, DN3 may not have eaten yesterday and didn't eat much the day before that. It also didn't help that the weather was cold and damp. Mom and Dad North are brooding based on the older nestlings, who no longer require daylight brooding unless it is raining, snowing, or unusually cold. DN1 and DN2 have thermal down, but DN3's thermal down was just beginning to come in and it would have benefited from brooding.
We suspect there is no one cause for DN3's death. The six-day difference between DN3 and its oldest sibling resulted in insurmountable developmental differences, including dominance interactions that DN3 always lost given its much smaller size, a resulting lack of food, and a lack of brooding before it was really able to thermoregulate on its own. Had the weather been warmer, DN3 might have been able to survive even given the shortage of food and dominance interactions with the older two, but all three together were too much.
Are Mom and Dad North bad parents? No. Eagles don't fit neatly into our human ideas about what good parents are. The older two have been thriving under their care. From an eagle point of view, there is no purpose in caring for weaker young that are less likely to survive than healthy young. Personally, I would love to have seen DN3 survive and I was very hopeful up until yesterday afternoon. But as someone who loves and watches birds, I also need to accept that this is what they do. Humans don't make good parents for birds.
Why didn't we intervene? What happened at the North Nest is completely normal from an eagle perspective. It is well-documented that the youngest member of a three-nestling clutch can die, even though we haven't seen it in Decorah or Fort St. Vrain (eaglets have died because of hypothermia and illness at FSV, but those were very straightforward deaths and didn't involve just the youngest sibling). We haven't intervened in these situations in the past and will not moving forward.
Watching wild creatures doesn't give us ownership over them. The lives of 'our eagles' are truly their own and this was yet another example of how we differ from them. Juliet Lamb has some excellent perspective on the relationship between watchers and watched here: http://daily.jstor.org/wildlife-cams/