Nest predation involving a California kingsnake (Lampropeltis getula californiae) and two fledglings of least Bell's vireo (Vireo bellii pusillus) was observed along the San Luis Rey River in northern San Diego County, California. The kingsnake was discovered consuming a fledgling when the adults were observed mobbing the snake. The kingsnake then proceeded to systematically search for the second fledgling by traveling out and back from the nest multiple times over the next 15 min, each time in a new direction, traveling ca. ≤6–10 m before returning to the nest. The snake then found the original roosting branch of the surviving fledgling and proceeded quickly toward the fledgling that had moved ca. 15 m away. The kingsnake traveled this distance in ca. 2 min and killed and consumed the last fledgling. While California kingsnakes have been reported to feed on birds and bird eggs, this systematic searching behavior has not been described previously.