Ok,
We have years of data concerning brood areas at different times of the year
in hives from all around the NW U.S.A. - in both full sized and nuc hives.
I can provide some summary information based on lots of years of work and
some projections from our bookeeping bee population models. The models
allow us to input the number of cells per frame, vary the queens
egg-laying, selectively remove some or all of the brood of any age, etc.
1. Brood frames and pollen gatherers:
As most of you know, a broodless colony often discontinues foraging for
pollen. You can have a large field force of forager, but they will be
bringing in nectar, not pollen. The point being made in the pollination
guidelines is not that the brood patches will suddenly provide foragers for
the crop, but rather that the presence of uncapped brood requires pollen
for the protein needed by the brood, and lots of it.
A quick rule of thumb regarding the brood status of a colony is to look at
the front entrance when the bees are flying. If they aren't bringing in
pollen, it's a good bet that they don't have any uncapped brood in the
hive. The queen may or may not be present.
Pollen gathering (numbers of bees) should scale in some manner to the area
of uncapped brood - unless the colony has large stores of pollen, all those
mouths need food.
2. Queen egg-laying rates:
Queens vary widely in their per day production. There are lots of myths
regarding good and poor queens. One is that large areas of contiguous
capped brood = a good queen = healthy brood.
The implication is that she lays systematically, filling cells as she goes
WITH the expectation that adjacent cells in any small area of the comb
should have brood of similar age. This is only partially true, and you can
check this by picking caps off of pupal cells. Some queens produce nice,
neat brood frames with a very uniform laying pattern. Other queens produce
brood patches that are also uniform in capping, but when you pick the cells
open, the pupae are of mixed ages. The queen lays in a spotty manner, then
comes back and fills in. If you have something that is killing early stage
brood, the queen may be able to mask this by the relaying. She just keeps
replacing eggs and larvae until you get a survivor in each cell.
3. One has to distinguish between a queen's egg-laying potential, and her
day to day laying rates.
In the spring, the queen can and may really crank out the eggs. But, our
models and data both indicate that the colony can only support the amount
of brood that can be fed and covered by the current bee population. At
about 2 brood (eggs, larvae, pupae) per adult bee, the colony seems to hit
an upper limit and either the queen shuts down and/or the bees remove any
additional eggs. This ratio seems to change somewhat with time of year.
The queen's egg-laying will also fluctuate with weather, forage, etc.
Later in the season, the upper limit for her egg-laying seems to be mostly
a function of available space (and I don't mean just count the cells per
side of a comb). During a nectar flow, brood nest cells get filled with
nectar during the day, which may later be moved to upper stores. The
number of cells available to be laid in is the total number of cells in the
brood boxes minus the number of cells already containing brood, pollen,
nectar, honey, etc. If you use a queen excluder to force the queen down,
and this space becomes even more constrained.
4. Queen egg-laying is often disrupted (to the point of shutting down)
when queen excluders are placed on hives and sometimes when stacks of honey
supers are added during a nectar flow (in which case, supercedure of the
existing queen may occur). We have seen this often in commercial beeyards.
5. My estimate, it is not uncommon for as many as 25-30% of the queens in
any large bee operation to be superceded within the growing season - and
the beekeepers have no idea that this is happening to this extent. Again,
we have the data to back this up. At least, it holds in the NW and parts
of the east coast.
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