I have had the bee block in the garden for a couple of years now, and I have seen some holes plugged up with what i presumed were bee nests, but I never saw the bees doing their work until today.
And I got pictures. How cool is that!
Also, please everyone, take a look at The Great Sunflower Project, an effort to study and quantify the condition of native bee populations in the United States and Canada. As honey bee colonies continue to have troubles from colony collapse disorder, scientists are studying ways that native bee species can take up the slack, and gardeners can help.
I have planted my sunflowers and intend to help the project. You can help out too.
Native bees nesting in my bee block.