Marbled Murrelet Surveys off the Central California Coast

Science Center Objects

Since 2017, the U.S. Geological Survey Western Ecological Research Center has continued long-term at-sea surveys of federally threatened Marbled Murrelets in central California.

Pair of seabirds on the ocean, with a roller coaster and rides on the shore

A pair of adult Marbled Murrelets at-sea off Santa Cruz, CA. Marbled Murrelets nest in old-growth Redwood trees in the mountains above the city of Santa Cruz. 

(Courtesy: Alex Rinkert)

Marbled Murrelets (Brachyramphus marmoratus) are small, cryptic seabirds—part of the same family as puffins—that live along the Pacific coast of North America. Unlike most seabirds, which nest in colonies at coastal islands and rocks, Marbled Murrelets have an unusual breeding behavior: they fly inland to nest alone, where they lay a single egg on the broad, moss- and lichen-covered branches of old growth forest trees. Due to loss of their old growth forest nesting habitat, Marbled Murrelets 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. Murrelets face threats to their ocean habitat as well, including disturbance from vessels and changes in forage fish abundance and availability. On land, increasing populations of corvids (ravens and jays) associated with human activities put eggs and chicks at risk of predation.

Map of the Central California Coast with survey sites marked along the coast

Map of U.S. Fish and Wildlife Service Conservation Zone 6 showing survey routes and Marbled Murrelet detections from Half Moon Bay to Santa Cruz, central California, 2019.

(Public domain.)

Information regarding Marbled Murrelet at-sea 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. Marbled Murrelets have been surveyed at sea off central California since 19951, and standardized surveys to estimate abundance and productivity have been conducted since 19992.

In 2017, the U.S. Geological Survey Western Ecological Research Center (WERC) began managing the at-sea monitoring program for Marbled Murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (San Francisco Bay to Point Sur in central California). In addition, the USGS WERC seabird studies team worked with past project leaders to compile and maintain a single database that included all survey effort and observation data to facilitate future analysis of this long-term dataset.

Scientists conduct the at-sea surveys from a small boat using line-transect methods1,2. Data recorded during the surveys include murrelet observations, GPS locations, bird behaviors and age-classes, and ocean conditions. Using the survey data, the scientists are able to estimate Marbled Murrelet abundance and an index of reproductive success each year. The results are published in U.S. Geological Survey Data Series annual reports, allowing wildlife managers to monitor the status of the central California population.

Three biologists on a boat look off to the left with binoculars

USGS biologists surveying for Marbled Murrelets off the Central California Coast.

(Public domain.)

Products

Annual Reports—

Felis, J.J., Kelsey, E.C., Adams, J., Horton, C., and White, L., 2020, Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2019 breeding season: U.S. Geological Survey Data Series 1123, 13 p., https://doi.org/10.3133/ds 1123.

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

Felis, J.J., Adams, J., and Kelsey, E.C.., 2018, Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2017 breeding season: U.S. Geological Survey Data Series 1093, 12 p., https://doi.org/10.3133/ds1093.

Prior annual reports (pre-2017) are available from California Department of Fish and Wildlife:

https://www.wildlife.ca.gov/ospr/nrda/jacob-luckenbach

 

Data Release (all years)—

Felis, J.J., Adams, J., Peery, M.Z., Henry, R.W., Henkel, L.A., Becker, B.H., and Halbert, P., 2019, Annual marbled murrelet abundance and productivity surveys off central California (Zone 6), 1999-2018 (ver. 2.0, March 2019): U.S. Geological Survey data release, https://doi.org/10.5066/F75B01RW

 

[Banner photo: Marbled Murrelets nest in old-growth Redwood trees in the mountains above the city of Santa Cruz. (D. Pereksta).]

[1] Becker et al. 1997

[2] Henry 2017 and references therein

 

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