Many bees (and other insects) can be found on blooming Willows early in the spring, including at least 6 Mining Bee species that are thought to be specialists. While willows are ubiquitous in most damp environments, they are often overlooked as a pollinator plant since the flowers are inconspicuous and often out of reach. Binoculars and/or a telephoto lens are very useful to fully appreciate one of the first spring pollinator shows.
Genus level ID: See the Mining Bee page for tips on separating other genera. In particular, compare the Unequal Cellophane Bee (Colletes inaequalis), which can be abundant on Willows and is superficially similar to a Mining Bee.
Many species of spring Mining Bees will visit willows, including many that are not identifiable from photo – in particular see subgenus Melandrena, which are common on willows and other spring flowers.
The species below are thought to be specialists and easiest to find on willows. They are in in rough order of abundance and distinctiveness. Click each box for more details on a given species.
Unless otherwise specified, photos are courtesy of Margarita Miklasevskaja at PCYU with funding from NSERC-CANPOLIN. Specialization data primarily from https://jarrodfowler.com/bees_pollen.html