I was hanging out laundry during the first spring (the one that lasted a week) and heard an odd sound coming from the bird feeder. The "plink, plink, plink" was sunflower seeds falling out of the feeder onto the squirrel guard as a honeybee burrowed among the seeds in the feeder. I watched for a while and saw that there were at least 10 bees engaging in this odd behavior, including 4 who had burrowed to the top of the column of sunflower seeds and were now stuck inside of the plexiglass tube.
I thought they might be looking for water, but the birdbath was full, and untouched. On the other side of the house, bees were working the crocuses like normal. On the clothesline side I felt like I was watching bees on drugs.
Now I used to keep bees and worked for a commercial beekeeper back in the "golden age" before mites made the business so difficult. I also worked in orchards and have observed honeybees in my spare time since I was a baby. I know what I am looking at when it comes to bees, and I've never seen such odd behavior in bees.
I have no idea what was causing it. If I see it again. I'll try to take some video.