Spatial resource distribution and phenology are critical factors for the development, emergence, and reproduction of solitary hymenopterans. However, the biotic and abiotic conditions that drive changes in their spatiotemporal distributions remain poorly understood. We surveyed the cavity-nesting hymenopteran community in a region of California oak-chaparral habitat over 3 y. Most taxa had short seasonal activity periods, with >90% of observations occurring within a single month for six of eight taxa studied. Predaceous wasps including Euodynerus foraminatus and Trypoxylon tridentatum were most abundant during the warmer mid-season months, while megachilid bees showed divergent phenologies consistent with temporal niche separation by species. Similarly, while some taxa were abundant and widespread across the study site, most showed relatively restricted spatial distributions. Spatial distributions were only partially explained by the dominant vegetation type; although some taxa showed significant preferences for oak- or chamise-dominated habitats, in most cases, differences in nesting abundance were not statistically significant. Parasitism rates ranged from zero to 57% among reared host taxa, with the relatively generalist Monodontomerus spp. as the most common parasitoids observed. These observations describe a community with strong within-population phenological synchrony, variation in species distribution patterns, and species composition influenced by spatial habitat heterogeneity.