The marbled murrelet (Brachyramphus marmoratus) is classified as a small seabird in the auk family Alcidae. It is the only living member of the genus Brachyramphus.
Taxonomy
The marbled murrelet was first described by Johann Friedrich Gmelin in 1789. Its scientific name comes from:
- Brachyramphus – from the Greek “brachys” meaning short and “ramphos” meaning bill, referring to the bird’s short bill
- marmoratus – from the Latin “marmoratus” meaning marbled, referring to the marbled brown and white plumage
It is classified in the following taxonomic hierarchy:
- Kingdom: Animalia
- Phylum: Chordata
- Class: Aves
- Order: Charadriiformes
- Family: Alcidae
- Genus: Brachyramphus
- Species: B. marmoratus
The marbled murrelet has no recognized subspecies. It is the sole living species in the genus Brachyramphus. Its closest living relative is thought to be the long-billed murrelet (Brachyramphus perdix).
Description
The marbled murrelet is a small, chunky seabird that ranges from 24-26 cm (9.5-10 in) in length and weighs 190-305 g (6.7-10.8 oz). It has the following physical features:
- Small head with a short, pointed bill
- Brownish-black upperparts with marbled pattern
- White underparts
- White “eye crescents” above and below the eye
- Short neck and wings
- Rounded tail
- Webbed feet for swimming
In breeding plumage, the marbled murrelet has a black crown, nape, and scapular feathers contrasted by white cheeks. In winter plumage, the black areas have white speckling or barring. The male and female look alike. Juveniles have dusky brown plumage with little marbling.
The marbled murrelet resembles a small murre or dove in flight. It has rapid wingbeats and flies on quick-turning zigzag paths low over the water. It can also hover briefly when hunting fish.
Measurement | Range |
---|---|
Length | 24-26 cm (9.5-10 in) |
Wingspan | 41-46 cm (16-18 in) |
Weight | 190-305 g (6.7-10.8 oz) |
Behavior
The marbled murrelet spends most of its life offshore and comes to land only to nest. Some key aspects of its behavior include:
- Feeds by diving underwater for fish and invertebrates
- Nesting – Nests in old-growth coniferous forests up to 50 miles inland from the coast
- Cryptic nesting – Lays its egg on a mossy platform high in a tree branch, with no nest construction
- Nocturnal nesting – Flies inland to nest sites only at night to avoid predators
- Vocalizations – Makes a dove-like musical trill and other calls at sea
- Migratory – Winters south to California and migrates north to breed
- Gregarious – Forms flocks of hundreds of birds offshore
The marbled murrelet spends winters clustered in sheltered coastal waters and bays. Starting in late March, adults make daily trips to shore to scout nest sites within old-growth forests.
Egg laying takes place from late April to early July. The female lays one speckled olive-brown egg directly on a wide mossy branch high in a conifer tree. Parents switch incubation duties and the egg hatches after 30 days.
The semiprecious chick remains alone in the nest being fed by parents returning with fish. After 28-40 days, the juvenile fledges and flies unaccompanied to the ocean.
Diet
The marbled murrelet is a marine bird that feeds by diving underwater and catching small fish and invertebrates. Its diet includes:
- Small schooling fish – anchovies, herring, sandlance, capelin, etc.
- Invertebrates – krill, shrimp, marine worms, mollusks
It feeds within several miles of shore, diving to depths of 30-70 feet to catch prey. The murrelet uses its wings for underwater propulsion while swimming. It will also hop on the water and pick prey from the surface.
Vocalizations
The calls of the marbled murrelet include:
- Loud musical trill or “keer” sounding like a dove coo
- Harsh “kraa-a” call in flight
- Rapid chatter calls at nest
- Downslurred “heeerr” call in courtship
These vocalizations are used for communicating at sea and advertising nest sites. The murrelet is most vocal at dawn and dusk.
Habitat
The marbled murrelet utilizes two very different habitats:
- Marine habitat – Lives and feeds in nearshore ocean waters, sheltered bays, and fiords. Requires areas with abundant small fish.
- Forest nesting habitat – Nests in mature and old-growth coniferous forests up to 50 miles inland. Requires mossy platforms on large branches for nesting.
It depends on coastal old-growth forests of redwood, Douglas fir, western hemlock, and Sitka spruce for nesting habitat. Marine habitat is also critical for wintering and foraging.
The two habitats together support breeding and other life history activities of the murrelet. Forest fragmentation and loss of nesting habitat is a major threat to this species.
Range
The marbled murrelet has a discontinuous breeding range along the Pacific coast:
- Aleutian Islands through coastal Alaska
- British Columbia, Washington, Oregon, and California
Its winter range extends south to Point Sal, California. Isolated wintering populations may also occur in Mexico.
The total population is divided into three main conservation zones:
- Zone 1 – Aleutian Islands and Alaska (about 25% of population)
- Zone 2 – British Columbia (about 30%)
- Zone 3 – Washington, Oregon, and California (about 45%)
Population and Conservation Status
The global population of the marbled murrelet is estimated at approximately 600,000 birds based on marine surveys. However, this species has undergone significant declines over the last century due to these major threats:
- Loss of old-growth nesting habitat from logging
- Increased nest predation from corvids
- Disturbance, fragmentation, and changes in forest structure
- Oil spills and gillnet fishing bycatch offshore
The population in California, Oregon, and Washington declined by over 60% between 1900 and 1987. Canada lost about 30% of its murrelets from 1987-2002.
Due to ongoing population declines and loss of breeding habitat, the marbled murrelet is federally listed as Threatened under the U.S. Endangered Species Act over most of its range. It is listed as Endangered in California, Washington, and Oregon. The species has legal protections under the Migratory Bird Treaty Act as well.
Conservation efforts focus on protecting existing old-growth forest nesting habitat. Artificial nest platforms have had mixed success in providing alternative nest sites. At sea, reducing oil spill risk, bycatch, and disturbance during the breeding season are priorities.
Conclusion
In summary, the marbled murrelet is classified taxonomically as a small seabird in the auk family Alcidae. It is a chunky brown and white bird that nests in coastal old-growth forests but spends most of its life feeding on fish offshore. This unique dual habitat reliance makes the murrelet vulnerable to habitat loss in both marine and forest environments. Due to declining populations from historical habitat loss and fragmentation, the marbled murrelet is federally listed as a Threatened species and receives legal protections. Ongoing conservation efforts aim to protect remaining nesting habitat and reduce threats at sea. The future of the marbled murrelet depends on maintaining suitable breeding habitat across its coastal range.