Yellow stripe on top of abdomen does not appear to continue around the underside.

Yellow-faced Bumble Bee (Bombus vosnesenskii) Approx length, 16mm. Yellow abdominal stripe DOES NOT continue around underside in this species. "There is a very similar species, Bombus caliginosus, that has a range that overlaps with Yellow-faced Bumble Bee (B. vosnesenskii). The easiest way to tell the two apart is to look at the yellow abdominal stripe. In B. caliginosus, it continues on the underside, while in B. vosnesenskii, the underside is black." Credit: domingozungri.

Photo comparison on BugGuide
https://bugguide.net/index.php?q=search&keys=Bombus+vosnesenskii
https://bugguide.net/index.php?q=search&keys=Bombus+caliginosus

Genus Bombus (Bumblebees) are our only native social bees. They are warm blooded allowing them to fly at cooler temperatures than most pollinators.
Native Bees https://openspacetrust.org/blog/native-bees/

Pollen Basket: The pollen basket is located on the bee’s hind legs and consists of hairs surrounding a concave receptacle. As the bee visits a flower, she grooms herself and brushes pollen sticking to her body toward her hind legs. She then packs the pollen into the pollen basket. To help keep the pollen together during flight, some nectar is mixed in. Hairs on the pollen basket hold it all in place. Amazing!

Kaufman Field Guide to Insects of North America, Eaton and Kaufman, 2006, p. 344-345.

Native Bees: Get to Know Native Bees of the Santa Cruz Mountains with Obi Kaufmann. May 6, 2020 https://openspacetrust.org/blog/native-bees/