Complex sentence: Colony decline happens during the summer months between the end of egg production and overwintering, however, because the females of "Lasioglossum hemichalceum" migrate between different nests, more than one nest exists at a time.
Split into simpler sentences: Colony decline happens during the summer months between the end of egg production and overwintering. However, because the females of "Lasioglossum hemichalceum" migrate between different nests, more than one nest exists at a time.