Reproductive Declines in an Endangered Seabird: Cause for Concern or Signs of Conservation Success?
Author Information
Author(s): Justin Schuetz
Primary Institution: Audubon California
Hypothesis
What are the patterns of variation in clutch size and fledgling productivity in the California least tern?
Conclusion
Despite a significant increase in the breeding population of California least terns, both clutch size and fledgling productivity have declined over the years.
Supporting Evidence
- The breeding population of California least terns increased from approximately 1,253 to 7,241 pairs during the study period.
- Clutch size decreased by approximately 0.27 eggs (14%) from 1990 to 2004.
- Fledgling productivity showed a similar pattern of decline and moderate increase even after controlling for clutch size.
Takeaway
Even though more California least terns are being born, they are having fewer babies and not raising as many chicks successfully.
Methodology
The study analyzed long-term data on clutch size and fledgling productivity from 27 breeding sites of California least terns between 1988 and 2009.
Potential Biases
Potential biases in clutch size estimates due to predation and abandonment were considered but deemed unlikely to significantly affect the results.
Limitations
The study does not fully understand the mechanisms behind the observed declines in reproductive success.
Participant Demographics
The study focused on the California least tern, a federally endangered subspecies.
Statistical Information
P-Value
p<0.0001
Statistical Significance
p<0.0001
Digital Object Identifier (DOI)
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