The Horned Mason Bee (Osmia cornuta) flies from mid of March until the end of April. They are a very good pollinator of all kinds of stone fruits, pears, and early kinds of apples. Also usable in strawberry tunnels and under foil.
The horned mason bee is a perfect addition for fruit complexes, even with enough honey bees, because unlike the honey bees are they even flying on colder days ( from 4°C with sun) and guarantee a pollination even under cool conditions.
Despite of its early appeareance is this kind of mason bee thermophile and lives just under 550 m AMSL. Its nesting sites need to be microclimatic convenient on sunny spots without wind.