Graduation Date

Fall 2023

Document Type



Master of Science degree with a major in Natural Resources, option Wildlife

Committee Chair Name

Dr. Daniel Barton

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Barbara Clucas

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Ho Yi Wan

Third Committee Member Affiliation

HSU Faculty or Staff


Human disturbance, Seabirds, Western Gull, Reproductive success, Behavior, Habituation, Subsidization

Subject Categories

Wildlife Management


Human disturbances can negatively affect wildlife by causing stress, altering behavior, or even impacting populations through changes in survival or productivity. Colonial-nesting seabirds are of particular concern due to population declines and their gregarious and conspicuous nature, which may attract human visitors. However, the effects of nearby human activities, though frequently negative, could be neutral or even positive through phenomena like habituation to human activities or subsidization by human-supplied food sources. In this observational study, I evaluated relative support for three hypotheses which may explain how Western Gulls are impacted by human activity: disturbance, habituation, and subsidization. I investigated this by comparing reproductive success and behaviors at two colonies of Western Gulls (Larus occidentalis) with different exposure to human activity. I estimated nest and chick survival for 110 nests located in northwestern California from May-September 2022, and quantified parental attendance for a subset of those nests. I found no difference in either measure of reproductive success between the two colonies, despite a clear difference in the frequency of potential disturbances. However, parental attendance was substantially higher at the high disturbance-risk colony. These findings may indicate that birds at the high-risk colony are habituated to or subsidized by human activities, and that efforts to reduce disturbance by limiting human activity near islands may be ill-suited for this area.

Citation Style

Journal of Wildlife Management


Thesis/Project Location


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