Walt and the Pollen Reserve and CCD
I have used Walt's "pollen box" maneuver for quite a few years now. For those that are unfamiliar, I'll describe how I do it:
I use one standard Langstroth deep for the brood nest in my colonies. As a general rule, I use shallows throughout the rest of the hive for a number of reasons. My overwintering configuration has one shallow beneath the deep, and either one or two shallows of honey above the deep.
My bees are located on the Alabama Gulf Coast, so all but my most northern yards have brood year round. By late January or early February, the buildup is well underway in my area and brood nests are expanding. This is when I checkerboard and add empty supers (shallows) above. As the season progresses, the brood nests will expand upward through the shallows (important to note the difference between expanding and relocating: during this expansion the base of the brood nest remains in the deep, sometimes including all 9 frames). When the shallow directly above the deep has at least 5 frames of brood, I put it to the side and inspect the shallow that is below the deep. Most of the time this shallow is empty, and if so I remove it and replace it with the shallow of brood. The empty is used upstack as a super. Occasionally the brood nest has been expanded into the lower shallow. In this case I just put everything back as it was.
When the colony begins to reduce brood nest volume, this shallow below the deep is backfilled with pollen as brood emerges. The pollen in this box is not the bright, colorful pollen I see at the edges of an expanding brood nest, but rather the dull, glazed, compacted pollen for long term storage.
This "pollen box" maneuver results in a boxful of pollen reliably and consistently in my area. My observations are just that; observations. No "science rigor", but these observations have, to this point, been repeatable. My overwintering success improved when I started using this technique. My colonies are also stronger at the beginning of the buildup than they were when I did not use the pollen box. (Note: to those that will point out that the improvements in my overwintering may have been the result of something else since I did not use the scientific method to prove that the pollen box was the cause of the success: you're right. It may be something else. But the improvements were across the board and coincidental with the change in my management practices.)
As to why I use shallows: first I will say that I do not intend to say one method is better than another, just why my method works better for me. Second, I usually do not use excluders. When the bees in my colonies begin to reduce brood nest volume as the season progresses, they (most of the time) start from the top of the brood nest and reduce down until the brood nest is back in the deep. Early on, I just assumed this was normal behavior. Then a few years ago I was short on shallow comb so had deeps and mediums on some colonies instead of shallows. When I was pulling honey at the end of the season, I found that in these colonies, the bees had moved the brood nest 2, 3, or 4 boxes up from where it started, and had completely filled the 3,4, or 5 boxes below them with pollen. I have played with this for the last few seasons and found that while the bees are content to expand the brood nest up into shallow boxes, they don't want the brood nest to end up there going into Winter. However, given deep or medium boxes above the initial brood area, they move the brood nest higher up the cavity, and have more pollen stored below. Note that the use of an excluder would prevent upward movement of the brood nest as or more effectively than the use of shallow boxes. (Again, I don't own or wear a white lab coat. Just observations.)
Ok, why did I explain all this boring stuff? Because I think the bees' pollen plan is, as Walt and Bjorn have pointed out, much more important than I used to and that it doesn't receive the attention it deserves. Also to point out that there may be some real merit to Walt's supposition that standard management with Langstroth equipment may seriously impair the colony's ability to manage pollen storage the way they "want" to. Given the opportunity, my bees almost always move the brood nest upstack and store huge quantities of pollen (1 1/2 or more deeps!) below the brood area. And this happens well before the Spring flow is over.
If this is what they "want" to do, and our management prevents them from doing so, what are the effects? Are they quantifiable? In a year where Mother Nature conspires to cause major pollen shortages, could the bees' ability to recover from our management practices be stretched past the limit, resulting in higher than normal colony losses (CCD)? I think that it is at least possible, and I'm glad there are folks like Walt and Bjorn and others to bring these ideas into the forum.