The Marbled Murrelet (Brachyramphus marmoratus) is a small seabird that lives along the Pacific coast of North America. This distinctive bird has dark brown upperparts and white underparts with brown mottling on the neck and breast. It nests inland in old-growth coniferous forests, flying miles out to sea each day to feed on small fish and invertebrates.
The Marbled Murrelet has declined significantly over the past century due to extensive logging of its coastal old-growth nesting habitat. It is now considered a threatened species under the Endangered Species Act in the United States and is red-listed in Canada. Determining accurate population estimates for the Marbled Murrelet has been challenging, but current data suggests there are likely less than 100,000 individuals remaining globally.
Population Status in the United States
The Marbled Murrelet population in the contiguous United States was estimated at around 81,000 birds in 2015 according to the U.S. Fish and Wildlife Service. This was down from an estimated 92,000 birds in 2000 and reflects ongoing habitat loss on federal, state and private lands. The vast majority of the U.S. population (77%) occurs in Washington, Oregon and California. Alaska likely holds several thousand additional Marbled Murrelets but comprehensive surveys are lacking in the remote coastal forests there.
Washington
Washington harbors over half (51%) of the total U.S Marbled Murrelet population and is considered the stronghold for the species. Population surveys in 2015 estimated there were 36,308 birds in Washington, with the highest densities found in the Olympic Peninsula, northern Puget Sound and southwest Washington. These estimates were down 8% from 2000 and continuing declines are expected due to logging of remaining old-growth nesting habitat on state and private timberlands.
Oregon
The 2015 population estimate for Oregon was 10,975 Marbled Murrelets, representing 13% of the U.S. total. Major populations occur along the central to northern coast. Numbers have declined since 2000, especially in the Siuslaw National Forest where extensive logging has reduced suitable nesting habitat. Continued losses are predicted for Oregon.
California
An estimated 9,192 Marbled Murrelets occurred in California as of 2015, making up 11% of the U.S. population. The northern California redwood region holds the majority of the birds, with smaller numbers scattered south to Santa Cruz County. Logging of remaining old-growth redwoods on state and private lands is driving ongoing population declines.
| State | Estimated population in 2015 | Percentage of U.S. total |
|---|---|---|
| Washington | 36,308 | 51% |
| Oregon | 10,975 | 13% |
| California | 9,192 | 11% |
Other U.S. States and Alaska
Smaller Marbled Murrelet populations likely persist along the outer coasts of Alaska and B.C., but insufficient survey data is available to accurately quantify numbers in these remote regions. Isolated breeding populations also occur in central California. Overall, Alaska may support up to 4,000 additional Marbled Murrelets while the total for central California is likely under 1,000 birds.
Population Status in Canada
Canada contains vitally important habitat for the Marbled Murrelet along the southern coast of British Columbia and southeast Alaska. Population data comes largely from boat-based surveys which can miss nesting birds inland. The most recent study in 2011 generated a coarse estimate of 75,000-110,000 Murrelets in the combined B.C.-Alaska region, but numbers are highly uncertain.
More localized monitoring does indicate that Marbled Murrelet populations are declining across much of coastal B.C. due to continued old-growth logging. A 2020 assessment found that numbers had dropped by 30-70% over the past three decades in several key monitoring areas on Vancouver Island and the mainland coast.
British Columbia
About 30,000-80,000 Marbled Murrelets are thought to nest along the coasts of southern B.C. based on extrapolations from boat surveys. However, inland breeding populations remain very poorly documented despite ongoing habitat losses, especially on Vancouver Island where the last unprotected old-growth is rapidly dwindling.
Southeast Alaska
Boat surveys suggest that between 35,000-50,000 Marbled Murrelets may live along the forested Alexander Archipelago coastline in southeast Alaska. But again, inland nesting populations are not well quantified and these offshore estimates could be biased low. More thorough monitoring is needed to refine status and trends in Alaska.
Other Global Populations
Small remnant Marbled Murrelet populations likely persist along the Kuril Islands and Kamchatka Peninsula of the Russian Far East, though little recent information exists. Japan may hold up to 1,000 birds. Isolated endangered populations also occur in China.
In total, these Asian populations likely number fewer than 5,000 Marbled Murrelets. They face similar threats from logging of coastal old-growth forests. More status surveys are needed to confirm numbers across the species’ full range.
Total Global Population Estimate
Summing up the available data, the total global population of the Marbled Murrelet can tentatively be estimated at 96,000-106,000 birds as of 2015. However, large gaps in population data exist for Alaska, British Columbia and Asia, along with uncertainty over the rate of ongoing declines across the species’ range. The global population could be higher or lower than this estimate.
Regardless, the Marbled Murrelet has clearly declined from historical levels due to extensive logging of its old-growth nesting habitat over the past century. Remaining populations face precarious futures in many areas unless further habitat losses can be prevented through improved forest conservation.
| Region | Estimated Population |
|---|---|
| Contiguous United States | 81,000 |
| Alaska | 4,000 |
| British Columbia | 30,000 – 80,000 |
| Southeast Alaska | 35,000 – 50,000 |
| Asia (Russia, Japan, China) | 5,000 |
| Total Global Estimate | 96,000 – 106,000 |
Research Needs
While the broad global population status of the Marbled Murrelet can be approximated from existing data, large knowledge gaps remain. Improved quantitative surveys and monitoring are needed, especially to track inland nesting populations that can be hard to detect from boats offshore. A lack of recent population data hampers status assessments across the Russian range. More refined habitat mapping is also required to model distribution and project future declines as coastal forests are lost. Tracking fledging success and adult survivorship relative to habitat trends would provide greater insight into mechanisms behind population trajectories. Increased research efforts focused on the status, ecology and conservation of the Marbled Murrelet across its range are vital to guide appropriate recovery actions.
Conclusion
The Marbled Murrelet is a threatened seabird that nests in old-growth coastal forests along the North Pacific. Current global population estimates suggest there are likely between 96,000-106,000 birds remaining. The core of the population occurs in Washington, Oregon and California where decades of logging ancient nesting habitat have caused ongoing declines. British Columbia also holds significant numbers of Marbled Murrelets but populations are poorly monitored and appear to be decreasing sharply in areas with continued old-growth logging. Smaller populations persist in Alaska and Asia where more data is needed on current status and trends. While substantial uncertainty exists over exact numbers and rates of decline across the Marbled Murrelet’s range, the species has clearly lost much of its original population and remains vulnerable to further habitat loss in coastal ancient forests. Increased conservation action informed by further research and monitoring will be key to ensuring the long-term viability of remaining global Marbled Murrelet populations.
