iNat had different recommendations for each picture, fuzzy-horned bumblebee and Vancouver bumblebee were two, the other two weren't bees. I lifted up a yard-waste bin I had sitting in the yard for a long time and found a bee nest! I used the container for its intended purposes then carefully placed it back at night. The bees were actively covering their exposed nest in the interim, and had got it mostly covered in a few hours time.

One video shows the mating behavior of many males around a female that emerged recently, and the other videos show some of the male activity over the nesting area as they search for emerging females. It's hard to capture how many bees were active and how impressive of their activity is in both sight and sound, but these videos give a limited sense of it, although you'll have to imagine the immersive buzz the bees made all around me unless/until I can extract audio to upload as a sound file. (By the way, the slight motion of the background relative to the foreground in the videos is an artifact of processing used stabilize the hand-held video so it doesn't jump around.)

The still photos show new nests (indicated by the fresh sand piles) being dug by females that have already emerged and mated. Over the past few days, the number of new nests went from a few to dozens in several nesting areas I've observed throughout this area; nearly all of the nests in the last two photos were new since I searched that sand ridge a few days ago.

Here's an approximate timeline of activity for these bees based on my observations:

Around March 15, the first males became active. They were common and active around the flowering manzanitas and huckleberries; it looked like they were patrolling for females as well as occasionally feeding at the flowers (e.g., this observation).

About 10 days later, around March 26, males were actively patrolling nesting sites in the sand, although no new nest burrows were present yet. The first females became active and the first mating took place (e.g., this observation).

About a week later, around April 3, males became abundant and highly active around nesting areas, while some males still patrolled flowering plants (in this area still mainly manzanita and huckbleberry plants), and additional females became active along with more mating. The first large mating aggregations became obvious. New nest burrows were still rare (e.g., this observation and this observation).

Within days (by April 5), females that had mated were digging many new nest burrows (e.g., this observation and today's observation above).

For now, activity continues whenever rain stops, clouds thin, and temperatures reach the high 40s to mid 50s F.

Two female Pine Grosbeaks. They were foraging on a gravel road, and bathing in a puddle before shaking themselves off in a tree and then flying away. Very tame birds, as I did not even see them until I was about 15 feet away and they were unfazed that I had gotten so close.

Mapped location not exact for privacy reasons.