Technical Abstract: Continued declines in honey bee Apis mellifera populations have prompted further exploration of alternative, economically-viable managed bee pollinators of agricultural crops. The potential of commercially-managed, native blue orchard bees Osmia lignaria to augment honey bees in orchard pollination depends on a suite of factors, particularly how to enhance O. lignaria retention while optimizing even pollination throughout the orchard by varying their stocking density and nesting distribution within orchards. In 2011, we investigated how artificial nest box density and the number of cavities within nest boxes influenced O. lignaria retention and reproduction in a 61 ha almond orchard pollinated by a mixture of O. lignaria and A. mellifera in the southern Central Valley of California. We assessed how localized O. lignaria nesting affected total nut yield. Retention of O. lignaria females was significantly greater in orchard areas with high density nest boxes compared to areas with low density nest boxes. Females preferred nesting in high density (low cavity) nest boxes compared to low density, high cavity nest boxes. Although considerable nesting variation occurred between treatments and within the orchard, all measures of O. lignaria reproductive success (e.g., number of completed nests, number of cells, and sex of offspring) were greater in orchard areas with high density nest boxes than areas with low density nest boxes. Understanding the factors of O. lignaria retention, nest establishment and reproduction, pre-emerged vs. on-site emergence from cocoons, and the spatial and temporal distribution of bees in orchards will allow for designing better O. lignaria management strategies for use in large conventional orchards.