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California Assessment Found Western Gulls Stable at Colonies but Declining at Sea

Adult western gull standing on coastal rock at Point Lobos, California
Conservation · Population & status

California, USA’s first statewide Coast and Ocean Assessment found contrasting population signals for the western gull (Larus occidentalis): breeding-colony counts were broadly stable over the long term, while at-sea survey data showed a sustained decline and particularly low recent abundance.

The 2026 assessment combined long-running monitoring datasets to evaluate seabirds and shorebirds across the state. For western gulls, breeding data came from peak nest counts at Año Nuevo Island, Vandenberg Space Force Base and the Farallon Islands, with records extending from the late 1990s through 2023 or 2024. At-sea abundance was assessed from CalCOFI and Rockfish Recruitment and Ecosystem Assessment Survey observations, with spatial and seasonal variation accounted for in the analysis.

Colony counts showed little long-term change and increased during the more recent period. The at-sea pattern was different: western gull abundance declined by about 2% per year over the long term and by roughly 6% per year in the recent analysis. At-sea abundance during 2022–2024 was among the lowest levels in the historical comparison.

The report therefore characterises western gulls as stable at breeding colonies but declining at sea. The contrast illustrates why colony counts and marine surveys need to be considered together: they measure different parts of the population’s ecology and can reveal different trends.

Sources and image credit

  1. Harris, J. L., Waters, T., & Zulian, M. (2026). California’s 2026 Coast and Ocean Assessment. Ocean Science Trust.Primary statewide assessment released 23 March 2026. Western Gull colony data showed a long-term trend of −0.10% per year and a recent increase of 6.01% per year; at-sea data showed declines of 2.08% per year long term and 6.35% per year recently, with the latest at-sea status at the 9th percentile.
  2. California Ocean Protection Council. (2026, March 24). With a Landmark Report and Historic Investments, California Doubles Down on Ocean Health.Official state release confirming that the 2026 California Coast and Ocean Report was released on 23 March 2026.

Image: David Iliff — wild adult western gull photographed at Point Lobos State Reserve near Monterey, California, 20 May 2013; Wikimedia Commons Featured Picture and Quality Image; representative California species image, not a bird from the monitoring datasets · CC BY-SA 3.0 · Source

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