The marbled murrelet (Brachyramphus marmoratus) is a small seabird that lives along the Pacific coast of North America. This species has declined significantly in recent decades due to loss of nesting habitat and other threats. Understanding what has happened to the marbled murrelet can help guide conservation efforts for this species.
What is the marbled murrelet?
The marbled murrelet is a small seabird in the auk family. It has a chunky body shape with a short neck and rounded head. Its wings are pointed and relatively long compared to its body size.
Some key facts about the marbled murrelet:
– Length: 8-10 inches
– Wingspan: 16-18 inches
– Plumage: Black above with white below, mottled pattern on wings and back
– Diet: Small fish and invertebrates
– Habitat: Nest in old-growth forests near the ocean, forage at sea
– Range: Pacific coast of North America from Alaska to California
The marbled murrelet has a unique nesting strategy. Unlike most seabirds, it does not nest colonially on cliffs or offshore rocks. Instead, it nests solitarily on large branches or mossy platforms high up in the canopy of mature and old-growth trees. This unusual nesting behavior makes it highly dependent on coastal old-growth forests.
Historical population and distribution
The marbled murrelet was likely always less abundant than other seabird species along the Pacific coast. However, historical records indicate that it was broadly distributed from Alaska to California prior to major human impacts.
Estimates of the historical population size are uncertain but may have been at least 700,000 birds before European settlement. The densest populations occurred in the productive marine environments of the Gulf of Alaska, British Columbia, and Washington. Smaller populations extended south into Oregon and California.
Decline over the past century
Over the 20th century, marbled murrelet populations declined dramatically across their range. The causes of decline include:
– Logging of old-growth and mature forests
– Development of nesting habitat for urban and industrial use
– Oil spills and gillnet fisheries bycatch
– Predation by corvids (crows, jays, and ravens)
Commercial logging was especially damaging to murrelet habitat. Clearcut harvesting rapidly removed enormous areas of the coastal old-growth forests this species relies on for nesting.
Some key historical milestones in the marbled murrelet decline:
– Early 1900s: Populations begin declining in Washington, Oregon, and California due to logging, development, and egg collection.
– 1970s-1980s: Sharp population drop (50-70%) in California linked to loss of redwood nesting habitat.
– 1989: Exxon Valdez oil spill kills thousands of murrelets in Alaska.
– 1990s: Continued declines up to 4-7% per year in Pacific Northwest from logging of remaining old-growth forests.
By the 1990s, loss of nesting habitat had reduced the estimated population to fewer than 700,000 birds across the full range. The rapid rate of decline triggered conservation concerns about the future viability of this species.
Current population status and threats
Marbled murrelets remain threatened by loss of nesting habitat as well as other factors. Conservation measures have slowed but not halted population declines in most regions.
The current population is estimated at approximately 396,000 birds. This represents a 44% reduction from the historical population size prior to logging and development. Here is a breakdown of the current estimated population by region:
| Region | Population |
|---|---|
| Alaska | 277,000 |
| British Columbia | 80,000 |
| Washington | 21,000 |
| Oregon | 7,100 |
| California | 2,160 |
Alaska now holds about 70% of the global population. The proportion is much higher than historically as declines have been most severe in the southern parts of the range.
Some ongoing threats contributing to continued population declines include:
– Old-growth forest harvesting in Alaska, British Columbia, and Washington
– Nest predation by corvids
– Oil spills and vessel disturbances
– Entanglement in fishing gear
– Changes in marine forage fish populations
– Climate change impacts on nesting and marine habitats
Logging is now more restricted in the Pacific Northwest than historically. However, it remains a threat in Alaska where large areas of coastal old-growth forest remain unprotected.
Predation pressure by crows, jays, and ravens has increased due to their association with human activities and food sources like landfills. Oil spills remain an ever-present danger. And climate change may alter the marine food web and impact nesting habitat suitability over the long term.
Legal protections and conservation status
Due to severe population declines, the marbled murrelet was assessed as federally Threatened under the Endangered Species Act in 1992. This protective status applies across the contiguous US range of the species in Washington, Oregon, and California.
Listing under the Endangered Species Act prohibits “take” of murrelets and requires federal agencies to ensure activities do not jeopardize the species. It also spurred development of a Recovery Plan outlining actions needed to restore populations.
In Canada, the marbled murrelet has been assessed as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) since 2000. However, it has not yet been officially listed under the federal Species at Risk Act. British Columbia has designated the murrelet as Threatened under provincial endangered species legislation.
These legal protections have helped reduce impacts from logging, development, and oil spills. But additional habitat protections and threat mitigation will be needed for populations to recover to sustainable levels.
Conservation efforts
A variety of conservation efforts have been implemented to try to stabilize marbled murrelet populations:
Habitat protection
– Higher density nesting habitat has been protected through parks, reserves, and “habitat conservation areas” on federal and state/provincial lands.
– Stricter regulations on logging practices on public lands. For example, buffer zones around occupied nesting sites.
– Acquisition of forest lands by conservation groups to protect as reserves.
Threat mitigation
– Restrictions on gillnet fishing methods that reduce murrelet bycatch.
– Requirements for oil spill prevention and response plans to minimize impacts.
– Management of corvid populations in some areas through removal or taste aversion conditioning.
Population monitoring
– Range-wide breeding season surveys to track population trends over time.
– Radar surveys to assess at-sea distributions and identify important marine habitat areas.
– Banding studies to obtain survival and movement data.
Public outreach
– Education programs to increase public awareness and support for murrelet conservation.
– Engagement with private landowners, logging companies, and fishermen to reduce impacts.
These efforts appear to have slowed the rate of population decline in Washington, Oregon, and California over the past two decades. But stabilizing and recovering populations will require sustained and expanded conservation action across the range.
Future outlook and recommended actions
Marbled murrelet populations remain depleted across their range and modeling indicates a continued high risk of future declines without significant additional conservation intervention.
To stabilize and recover murrelet populations, scientists recommend:
Habitat protection
– Establish large reserves protecting remaining old-growth nesting habitat blocks. Focus on areas with highest breeding densities.
– Extend habitat protections on federal forest lands in the Pacific Northwest.
– Strengthen habitat conservation in Alaska where extensive old-growth forests persist.
– Retain buffer strips and nest patches in logged areas to support some nesting.
Threat mitigation
– Enhance oil spill preparedness and restrict vessel activity in important habitat.
– Reduce fisheries bycatch through modified practices and gear restrictions.
– Limit corvid population growth through removal and reduced access to food sources like trash and landfills.
Monitoring and research
– Maintain long-term surveys to detect population trends.
– Study nesting habitat relationships and foraging ecology to inform management.
– Assess potential impacts of climate change.
Community engagement
– Provide economic incentives for conservation on private forest lands.
– Partner with indigenous communities on habitat stewardship.
– Promote marbled murrelet conservation values through public education.
With intensive management and habitat protection, scientists believe marbled murrelet populations could stabilize and eventually recover to healthy levels. But without bold, proactive efforts, this unique seabird will remain at high risk of continued decline. Sustained commitment from government agencies, scientists, land managers, communities, and the public will be needed to ensure the long-term survival of this threatened species.
Conclusion
The marbled murrelet has experienced dramatic population declines over the past century, primarily driven by extensive loss of coastal old-growth nesting habitat. Conservation measures have slowed but not halted drops in numbers, and the species remains federally listed as Threatened in the contiguous United States. Ensuring the future viability of marbled murrelet populations will require a concerted effort across their range to protect remaining habitat, mitigate key threats, closely monitor trends, and engage local communities in stewardship. With active management informed by science, it may be possible to restore marbled murrelet populations to healthy levels. But the fate of this seabird depends on our collective commitment to conserving the magnificent coastal and marine ecosystems it represents.
