Abundance and Productivity of Marbled Murrelets (Brachyramphus marmoratus) Off Central California During the 2018 Breeding Season

Data Series 1107
By: , and 


Executive Summary

Marbled murrelets (Brachyramphus marmoratus) have been listed as “endangered” by the State of California and “threatened” by the U.S. Fish and Wildlife Service since 1992 in California, Oregon, and Washington. Information regarding marbled murrelet abundance, distribution, population trends, and habitat associations is critical for risk assessment, effective management, evaluation of conservation efficacy, and ultimately, to meet Federal- and State-mandated recovery efforts for this species. During June–August 2018, the U.S. Geological Survey Western Ecological Research Center continued previously established, long-term (1999–2018), at-sea surveys to estimate abundance and productivity of marbled murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (San Francisco Bay to Point Sur in central California). Using conventional distance sampling methods, we estimated marbled murrelet abundance using 137 detections of 227 individuals observed on 9 surveys. The abundance estimated for the entire study area using all surveys in 2018 was 370 birds (95-percent confidence interval, 250–546 birds). Estimated abundance from 2018 is comparable to most prior years of study, except for 2001–03, when greater abundances were estimated. In 2018, we estimated reproductive productivity (calculated as the hatch-year [HY] to after-hatch-year [AHY] ratio) using four detections of four HY individuals observed on six surveys. After date-correcting HY and AHY counts to account for birds expected to be absent from the water while inland at nests, the date-corrected juvenile ratio was 0.047 ± 0.024 standard error. We updated a synthesized database of all Zone 6 marbled murrelet survey data since 1999 with 2018 data to allow scientists and managers to evaluate established survey methods and assess trends in abundance and productivity estimates.

Suggested Citation

Felis, J.J., Kelsey, E.C., and Adams, J., 2019, Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2018 breeding season: U.S. Geological Survey Data Series 1107, 10 p., https://doi.org/10.3133/ds1107.

ISSN: 2327-638X (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Methods
  • Marbled Murrelet Abundance and Productivity Results
  • Discussion
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2018 breeding season
Series title Data Series
Series number 1107
DOI 10.3133/ds1107
Year Published 2019
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Western Ecological Research Center
Description Report: v, 10 p.; Data release
Country United States
State California
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details