Historical changes in black brant Branta bernicla nigricans use on Humboldt Bay, California

Brant Goose (Branta bernicla) Science Article 1


We examined 70 years (1931-2000) of black brant Branta bernicla nigricans abundance on Humboldt Bay, California. We used linear regression to convert count data to a standard variable (use-days) for evaluating hypotheses that explain temporal trends in brant use. Winter and spring brant-days on Humboldt Bay declined sharply in the mid-1950s and continued to decline through the mid- 1980s, but have since increased. Evidence suggests that this trend may have been driven largely by changes in temporal patterns of hunting pressure on Humboldt Bay. We found little convincing support for alternative hypotheses such as changes in eelgrass Zostera marina condition over time, effects of non-hunting disturbance, and correlation with trends in abundance at the flyway level. Our study affirms the appropriateness of current hunting regulations for brant in California, but poses a challenge to wildlife managers who wish to provide hunting opportunities without displacing brant from important staging and wintering areas.

Jeffrey E. Moore & Jeffrey M. Black, Wildl. Biol. 12: 151-162

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