During the prior three years We believe that the first egg was laid on December 13, 18 and 11. This year, based upon an undocumented observation, we believe that the female assumed and maintained an incubation position beginning on December 11, 2011. Two days later, on December 13, the nest appeared to be empty over a 15 minute period. The next day and again on December 16 the female was reported to be sitting very low in the nest.
Based upon ground observations during the prior three years, the first egg hatched 35, 34 and 35 days after being laid. This year, on January 15, the adults exhibited a change in behavior that strongly suggested that the first egg had hatched. This was 35 days after the presumed day it was laid.
In past seasons an eaglet was first seen from the ground at the age of 23, 18 and 7 days (average 16 days) respectively. This year it was sighted on day 18.
Pre-flight branching (climbing out on branches in the nest tree) and "helicoptering" (hovering a few inches above the nest) was observed when the oldest eaglet was 69, 73 and 60 (average 67) days old , respectively. As of yesterday, March 20, the eaglet was presumably 65 days old and had not yet exhibited this behavior.
This raises an interesting question. Is it possible that this year's eaglet is actually younger than we assume? Might it have been the product of the second or third egg that was laid, up to a week later than the first? It is possible that one or more of the other eggs was infertile or was destroyed.
This year's eaglet also behaves differently than those in previous seasons. It tends to be rather passive. While it calls loudly to be fed, it assumes a subordinate posture once the adult arrives to feed it, crouching low in the nest. It also waits quietly while the adult tears off portions of prey. In past years, the older and larger eaglet competed vigorously to be fed. The younger nest-mate(s) generally stood by and sometimes the parent had to actively feed the younger chicks. We have even seen the parent block the older eaglet to prevent it from continuing to monopolize the meal.
When the eaglets were nearly full grown (as is the case now), they would actually attack the parent when it brought in food, even causing it to simply drop the prey in the nest. In contrast, this year's eagle chick seems to wait until the food is cut up into small portions by the adult. We have seen it pick at prey, but then begin calling as if it needed to be fed.
Our theory is that the lack of competition from siblings may be the cause for the submissive behavior of this eaglet. Further, based upon comparative developmental milestones, it may be as young as 57 days, rather than 65 days as we have assumed. These are only hypothetical assumptions, but we will be interested if other observers confirm or challenge them.
Re: Why is there only one eaglet, and how old is this one? COMMENT PLEASE
Thanks Ken - this has a lot of good info that I have always wondered about in the 3 years I have been going to see this nest. I see this chick as very small, compared to past years at this time, when they were huge and getting up on branches above the nest - and I was wondering about what the age of it might be. Also, this year, I see the parents as much more attentive and they both seem to be on the nest together more than in years past. I find it all fascinating and I am so glad I found this forum.