Last year, John Blakeman offered some perspective on the significance of the evergreens and greenery in the nest, and I thought it would be helpful to repost his thoughts:
"Nest watchers have noted that the haggards bring sprigs of evergreens into the nest. Almost all red-tails do this, for really unknown reasons. But when they appear, it's a sign of profound commitment.
The conventional explanation is that these pine or spruce twigs have fragrant volatile chemicals that drive off feather parasites. Indeed, such vapors do emanate from evergreens, and there must be a few bugs at a nest with evergreen sprigs. And yes, red-tails can have small populations of tiny feather lice. But these are seldom seen, and cause no health or feather problems in healthy birds. I have never been able to discover any of these on my falconry red-tails.
So repelling arthropod (bug) parasites is not really a factor.
And in fact, just look at where the haggards place the evergreen sprigs. If they are brought to the nest to drive out feather bugs, they aren’t in the right place. Most of them get placed out on the rim surface, where the birds stand, not where they squat. The aromatic vapors from these can’t effectively penetrate through the feathers to the birds’ skin surfaces, where the feather lice (what few there are) reside.
Frankly, the birds themselves keep the feather bugs in control by their frequent and prolonged preening. Nest watchers will see a lot of this, with a bird just standing there with its head turned around and probing through feathers all over its body.
But the evergreen sprigs? They can’t be there to repel bugs. Wrong placement.
I really think they’re just really decoration, making things a bit more pretty (well, chromatically luminous for my academic colleagues) than just the bare sticks. I also think it behaviorally conveys commitment by the birds both to the nest and to each other. I don’t think unpaired red-tails ever carry around or do anything with evergreen sprigs.
For fun, I’ve tossed a few of these into my falconry red-tail’s chamber in March, and she does absolutely nothing with them. She pays no attention. It’s obviously a nesting and perhaps a pair-bond thing.
"Here, I brought you this. It shows I love you, and I like our nesting pad here. Don’t we got it good?"
And yes, my academic colleagues will cringe, as I internally do when I present such anthropomorphisms. No, red-tails don’t converse or even think lubby-dubby thoughts. It would be an error to explain what we are seeing in such thoroughly human or mammalian terms. Biologically, it’s not so clearly parallel.
But on the other hand, there are distinct behavioral parallels, although they are not neurologically exact. Hawk brain structure is very different from ours, and they can’t think too deeply on much of anything. Their behaviors are rather ritualistic, just going through the motions, as it were. Their brains aren’t big enough for much more than this.
But that should not discount all the wonderful behaviors we are privileged to watch. It can’t be denied that this is a committed, reproducing couple, tending diligently to bring a new generation of their offspring successfully into the Philadelphia skies. I’m as addicted to watching all of this as everyone else. I’m doing this because it’s just so profoundly exciting and fun, to be able go right in the living room and neighborhood of this bird family. We get to see it live and in person. How exciting, for each and all.
Once again, nothing like it in all the world."
Today, on a gorgeous May morning, the ever-growing eyasses showed off their huge feet, as they sat back and preened after breakfast.
Then follows the predictable nap after eating.
Sometimes, they appear to be doing face plants as they sleep!
When they awaken, they often do some preening, but their balance is still shaky and they tend to slip sideways as they work their beaks through their downy fluff.
This afternoon, the tiercel unaccountably decided to bring a plastic grocery bag to the nest, much to the astonishment of his eyasses.
He returned to deliver a mouse snack, by which time the bag was no longer such a startlement. But the big surprise, however, was the greed of the eyass who grabbed and swallowed the mouse whole. The eyass is even demonstrating mantling behavior - dropping its wings to cover and protect the food from others who might want to steal it.
He was then out for the count, while one of the other eyasses amused itself by exploring the bag.
Later on, the formel arrived with a large pigeon which she ripped up to feed them.
They moved in and started pulling off pieces themselves
As each eyass got stuffed full of pigeon, it slumped down in a food torpor.....
.... until the last one standing got the final morsels stuffed into its bulging crop by the formel
... and then all three got ready for another nap as the formel watched over them.
These haggards model perfect parenting as they provide food, shelter, security and consistent attention to their offspring, and we are fortunate enough to see it all happen from four feet away.