Phenology Report, March 15 2022
Ready or not, it’s time for this week’s phenology report! In an average year, this week would be a great time to look for eagles on their nests. The heavy snows this year, however, are preventing the eagles from accessing their nests. While we and the eagles wait for the snow to melt, John offers us a longer version of the ‘eagle-centric’ article he wrote for the February-March edition of The Senior Reporter:
In a patch of aspens just west of the house there is an eagle’s nest. It hasn’t always been there. In the mid 1980’s, a pair of eagles began constructing a nest in a white pine near the aspens. The white pine had been girdled by porcupines and the top was dying. This afforded the eagles easy access to the tree.
I built my house in the late 1970’s and the eagles came along in 1985 and began building their nest. If they had begun first, I would have been prevented by laws designed to protect eagles from building as close to the nest as I am. They chose to tolerate me as a neighbor, not the other way around.
The white pine served as their home for fourteen years. On November 6th I wrote the following note in my journal:
Sometime in the last few days the eagle’s nest has fallen. Most likely it was on the first since we had strong winds from the southwest that day. From 1985 till 1999 they were our companions. Many of their young came into or yard as they were learning to fly. One even sat on our deck rail.
You can get a feeling of my sense of loss and despair. Six days later I wrote these words in my journal:
The eagles who had previously lived in the recently fallen nest have begun to re-build their nest. They have picked a popple (P. tremuloides) with a fork at the top. Sticks are being added regularly.
Until that moment I had paid little or no notice of the popple. The eagles, on the other hand, must have been studying it all along. From their nearby perch in the white pine it must have given them a sense of strength and utility. The fork at the top was actually four stout branches forming a natural base for a nest.
I was dubious. Aspens are not known for their strength. If you put a quarter of a ton of sticks in the top of an aspen, the weight alone would seem to be enough to cause failure. Couple that with the size of the nest acting as a sail against any wind and I didn’t give the nest much of a chance to succeed. Sixteen years later, they began building a new nest east of the house and across a tamarack swamp. This time they selected another white pine.
This pine offered a dead top with several bare, open, easily accessible branches to perch upon. I couldn’t blame them for choosing to move. I was amazed that the aspen hadn’t snapped off in any one of dozens of strong wind events over the intervening years. The fact is that the nest in the aspen still remains. Standing tall and proud, the only telltale sign that it is not occupied is the smooth exterior. As the branches rot, the winds strip away the protruding ends and the nest takes on an unnaturally smooth look. Regularly attended eagle’s nests are constantly being refurbished. The new nesting material leaves the exterior looking a good deal more unkempt than an abandoned nest.
The presence of the nest brought my attention to the aspen. I hadn’t been keeping records on that particular tree. Once the eagles had selected it, I began to watch more carefully its phenology. It turns out that it is member of a clonal patch of trees ten in number. All are quite close in age if trunk size is any indicator. All of these clones are late to leaf out in the spring. A fact that originally had me thinking they might be big tooth aspen. A close inspection confirmed that they are trembling aspens. They also hold their leaves later in the fall. Whether this had something to do with the eagles’ selection I can’t say. Somehow they were able to defy my judgement and select a tree ideally suited to the task.
This is the time of year when eagles return to the north. Truth be told many don’t bother to migrate south at all. Increasing numbers of eagles have kept many in the north all winter. They don’t always stay around the nest, but from time to time they make a visit. The expansion of the deer herd and the resulting road kills provides the eagles with much of the food required to stay warm and healthy. Any stretch of open water will support a population of eagles not inclined to head south for the winter.
My records confirm that the eagles return to the nest every year in February. Typically one shows up and then within a day or two the mate shows up. There is always a period of re-acquaintance signaled by soft calls between the two. Shortly after they begin the process of adding to the nest. Both birds will bring sticks to the nest though not all are found suitable to the feng shui. The base of a tree containing an eagle’s nest is littered with discarded branches.
After the eagles have added the new sticks they begin to bring grasses to line the bottom of the nest. In August of 1989 I climbed up and into the nest near my house. Using ropes to ensure that if I did fall, it would only be a short distance before I would be arrested, I clambered over the edge. The nest had a slight depression in the middle with most of the bottom lined in grasses. It was far from the cup nest made by most small birds. I could have curled up in the bottom and slept comfortably.
Once the nest has been rehabilitated the female settles in to begin laying eggs. Last year, that appeared to be around the 12th of March. She begins to brood the eggs as soon as the first one is laid. This staggers the hatch so that the birds are at least a day or two apart when born. The advantage goes to the first born. They will make sure that they are fed before the second or third eaglet is fed. In this way, if the hunting is particularly poor at least one will survive. If the parents are good hunters, or if the food supply is plentiful, the chances of survival for the subsequent offspring are improved.
There was a time when even seeing an eagle was a remarkable stroke of good luck. Pesticides caused the eagle eggs to be so fragile that the weight of the parent was enough to shatter the egg. Luckily it was discovered and the pesticide was banned. Now the population has rebounded to the point that almost anyone on any given day will see an eagle. And this time of year, watch to see if they aren’t doing some home improvements.
This is the time of year that the eagles should be back, and potentially even sitting on eggs! Last year, the eagles were on their nest on March 12th, and the average tends to be in the first week of March.
While going through old photos, John stumbled across a picture of his house in March of 2019. The snow was up to the eaves, just like it is this year! The similarity struck him, so he dug in to his records. He found a photo from April 10th, 2019, depicting a speckled alder just beginning to flower. The average flowering date is about a week earlier. The same pattern was found in the red elderberry (average flowering date is March 6th or 7th; in 2019, it flowered on April 14th) and the hazels (average flowering date is April 8th; in 2019, they flowered on April 15th). The pattern is very suggestive- in 2019, when the snow cover was similar to this year, spring was a week lake. It’s likely we will see the same pattern this year, or at least that’s John’s prognostication! (I had to look that one up: prognostication is defined as “the action of foretelling or prophesying future events.”)
Enjoy the warming weather, even if it comes a week late!
Remember you can add your voice to our phenology talkbacks show! Get in touch with me (firstname.lastname@example.org), John (email@example.com), or text ‘phenology’ to 218-326-1234.