Suga, I looked back through the threads of 2015, and found a
post about this very thing. The post # 866262 dated May 30, 2015
by Clint Brown shows a photo on post # 874968 by permascapes
regarding this bee behavior.
The photo shows the bees have gathered masticated plant material
to use as a plug to seal the hole of the nest which contains the bee's eggs.
It appears to me to be a similar bee as you have pictured.
Hope this helps some.
