The widow skimmer, Libellula luctuosa, is a perching dragonfly commonly found across North America, including in California. Males are known for their distinct brown and blue wing coloration, but this pattern can be hard to see in the less colorful females. They hunt prey from a perch, darting off to grab if before returning to it with their meal. During the breeding season, males are territorial of their perch, and will chase off other males that get too close.
Sketch & fact by Christofer Brothers.
Reference: Campanella, P. J. (1975). The evolution of mating systems in temperate zone dragonflies (Odonata: Anisoptera) II: Libellula luctuosa (Burmeister). Behaviour, 54(3-4), 278-310.