Air layering oddity

Ok, so i decided this year I was going to take a shot at doing some air layering. My first victim subject is a pear tree that produced like mad this year. We moved here in May and the house and property had been unoccupied for 35 years previously, so this tree hasn't been trimmed in at least that long. I picked a few new growth branches that were about pencil size or larger and did them like normal. I also had a branch that was growing out of the side of the main trunk about a foot from the ground that is around the size of my wrist. It grows straight up into the middle of the tree. I decided that it would be one that would need to be trimmed, but instead of trimming, I wanted to try to air layer it. I got a one and half gallon container so that it could try to make plenty of roots. The branch is probably ten feet tall and has a few other branches coming off of it. I'm not even sure this is possible to be air layered, but I figured i haven't lost anything if it doesn't work. My oddity is that of this giant pear tree, all of the leaves have already turned colors and fallen off of it, EXCEPT the branches that i air layered. They are still beautiful and green. Is this normal? I did use aluminum foil around the plastic containers that I air layered with to help seal in some moisture, and i was guessing that maybe they are keeping the roots inside warmer in the sunshine, but then that would also be bad when we've had 30 degree nights already, the foil would make the roots colder. Anyway, any help or insight would be greatly appreciated.

Ah. I think I might have an answer for you. I assume you girdled the branches for air layering? When girdling, you stop the flow of cytokinin from the roots, thereby reducing the cytokinin/auxin ratio (auxins are produced in buds, cytokinins in root tips). The reduced c/a ratio is actually what induces rooting. By contrast, an increased c/a ratio promotes growth of lateral buds. The point is that cytokinin and auxin have roughly opposite effects, and the relative abundance of the two determines what happens. Now, Wikipedia says this:

Auxin inhibits abscission prior to the formation of the abscission layer, and thus inhibits senescence of leaves.

As far as I can tell, that means that a low c/a ratio (a lot of auxin compared to cytokinin) will inhibit leaf drop, and that's exactly the kind of situation that girdling creates. Hormones are funny.

That's actually a pretty common (and encouraging!) thing to see with air-layered branches. When you girdled the stem, you blocked the normal downward flow of hormones, especially cytokinins, from the roots. Meanwhile, auxins coming from the buds get "stuck" above the girdle. High auxin levels are exactly what trigger rooting, but they also slow down leaf aging and delay leaf drop. So those sections basically stay in their own little hormonal bubble while the rest of the tree gets the signal to shut down for winter.
It doesn't mean anything's wrong. If anything, it suggests the layers are still alive and actively trying to root. You might just need to give them some extra time before separating them.