We supported management of the California Least Tern (CLT) Preserve at Huntington State Beach by establishing a baseline of nocturnal small mammals relevant to nest depredation risk. In Year 1 (Oct 2024–Aug 2025), we deployed 30 Sherman live traps across three arrays (north, southeast inside fence, southeast outside fence) for three consecutive nights (90 trap-nights). We recorded five captures, all House Mouse (Mus musculus), yielding 5.6 captures/100 trap-nights and 0 recaptures. All detections occurred on the southeast perimeter (inside and just outside the fence). Weather was cool and calm with waxing gibbous illumination during all trap nights, a factor known to suppress nocturnal small-mammal activity and potentially bias detection low. Vegetation structure, tracks, and burrows identify the southeast perimeter as current high-probability use areas. These results provide a defensible baseline, refine trap placement for Year 2, and begin to separate habitat structure (riprap/vegetation/trash availability) from detection effects (lunar illumination). Management implications include prioritizing trash abatement at riprap edges, pre-season focused trapping on the southeast perimeter, and maintaining short, humane handling windows. Complementary daytime efforts targeting California ground squirrels (selective depletion; CPUE tracking) will proceed in spring to directly address a likely CLT predator. Ongoing integration with weekly CLT nest monitoring will link mammal activity to nest outcomes and guide adaptive effort in Years 2–3.