Monarchs recorded across the basin in July breeding season

July 28, 2026

(Danaus plexippus) have been turning up across the basin nearly every day this month — from the beach towns along the coast through Culver City, Pasadena, and up into the San Gabriel foothills, with two sightings at Ballona Wetlands on a single day last week. July is the summer breeding generation, not the fall migration; these are butterflies searching out milkweed to complete one more reproductive cycle before the autumn push south toward Mexican overwintering sites.

The western population crashed by roughly 99% by 2020, according to Xerces Society Thanksgiving Count data — a collapse driven by loss of milkweed across the landscape and pesticide use. Urban and suburban milkweed plantings across exactly this kind of fragmented, built-up terrain are considered a key factor in the species' prospects — a reminder that backyard conservation can matter at a continental scale. Yet not all milkweed is equal here. The tropical milkweed that lines many garden beds stays green year-round in the mild climate, which can cause monarchs to skip migration entirely and linger on plants that accumulate a protozoan parasite called Ophryocystis elektroscirrha. The sightings at Ballona are a reminder that even a heavily impaired urban estuary still draws this species — though what observation counts reflect about population status, observer effort, or habitat use is beyond what presence records alone can tell us.

Data from iNaturalist

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Elegant Terns bring ocean contaminants inland to their island colony

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July drought exposes Ballona Creek's cascading failures

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More about Monarchs

Monarchs and bumble bees converge on July milkweed corridor

July 28, 2026

butterflies have made three appearances along the corridor since early July, with the most recent sighting on Westcott Street on July 23rd. On the same week, iNaturalist flagged a on the Eastside — both threatened species that depend on milkweed, though in different ways. Monarchs lay their eggs exclusively on milkweed, and their caterpillars eat nothing else. Bumble bees work the flowers for nectar and are among milkweed's most effective pollinators.