Here are a couple photos from last year of some of the bees that were all over the spruce trees at my sister’s place in central Wisconsin. I was checking out the bees on the mountain ash that was flowering when I noticed the buzzing coming from the spruce trees next door. They were all over them. My guess is that maybe they were collecting propolis but I’m not quite sure.
I suspect your photos show propolis collection since the trees aren't covered with, nor are the bee's pollen baskets showing any pollen. I do think a bee would collect most any pollen if hungry enough (a problem here in California Buckeye land), and have observed carpenter bees harvesting grass pollen when there were plenty of other nearby pollen sources.
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