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Long story short, I'm feeding hive A, and Hive B. Both are about 10lbs underweight. Using 1/2 gallon feeders, one right after another, without more than a couple of hours between refills. 2:1 syrup.
Hive A has gained 8lbs after roughly 3 gallons of feed. Hive B has gained 8lbs after 1 gallon of feed.
WTF is going on here? No, the feeders aren't leaking. I'm losing my patience (and losing warm weather). >>>>
Huh, not gaining weight despite feed going away - a gallon of 2:1 feed is about 8 lbs...
1) robbing (covered already)...
2) just leaking out. Ruled out...
3) no way they are eliminating it as waste as fast as they are taking it!!!! If they are using the sugar syrup to feed brood, then.... the hive will still gain weight. Brood are made of lots of water! But perhaps... not as much weight if they are still feeding brood. So this may be playing a role. So, feed 16 lbs (2 gallons), gain 8 lbs... just guessing here.
4) losing bees, as in, winter bees were dying off. Perhaps hive A lost winter bees after hive B already did. It does not cost the bees a lot to check the cluster size; this is the point where PA (and OH) are at only winter bees; summer bees have died off. Worth noting/comparing cluster size.
Just a though - I wonder if hive A swarmed late, and are still building up? A younger queen will push broodrearing later than an older queen. And keep summer bees longer.
At any rate, it's all about having enough stores for winter, right? some thoughts below...
I have found that the ratio of honey to bees is more important that weight for gauging whether I'm in the green or the red for honey stores. So, if a deep has only 5 frames covered with bees, then they should have 5 additional frames with honey beyond what is covered. For NE OH overwintering, to calibrate. That's just an example - and we know that strong 5 frame nucs with 2 stories (10 total frames) do fine for overwintering.
Not that the OP has only 5 frames covered with bees!!!! just using numbers to anchor things.
So, if I am below the number of honey frames I want, I will put on a block of sugar - like, 10 lbs at a time - on a box with a mesh screen bottom, big enough holes the bees can climb up. Lots of ways to make the block -
https://www.honeybeesuite.com/no-cook-candy-board-recipe-for-feeding-winter-bees/ - for a recipe.
Every winter is a bit of a leap of faith for me. ;/ but so far, with overwintering deeps, long hives/top bar hives, and Dadant extra-deep frame hives, that principle of the ratio of 1 part bees: 1 part honey frames has held true.