The marbled murrelet is a pacific seabird that nests in trees in older coastal forests in North America and Asia. Within its North American distribution range, the marbled murrelet contains migratory and resident populations. The migratory populations summer in Alaska and Canada and travel south as far as northern California for the winter months.
Marbled murrelets belong to the Alcidae family. The Alcidae family is characterized by their short tails and wings, and stalky bodies. Puffins are also a member of the Alcidae family. Marbled murrelets weigh approximately 200 grams and are considered a “plump” alcid. Their plumage varies extensively with summer plumage being a molted blend of dark brown on a dark white background. During the winter months their plumage is a black and white pattern, usually with a white belly and throat.
In the winter and spring marbled murrelets predominately predate upon euphausiids, mysids, smelt, and herring, and occasionally feed upon pacific sardine, shrimp and sockeye. They forage in bays, inlets, fjords, and the open ocean within 5km of shore but prefer shallow water. In the open ocean, marbled murrelets can dive up to 60 meters and they propel through the water with their wings. Murrelets produce oil to coat their wings which helps them as they glide through the ocean.
Marbled murrelets breed and nest in mature and old-growth coniferous forests or forests with old-growth characteristics such as multi-layered canopies, large trees with large limbs or platforms created by damage, disease, or mistletoe within 50 km of shore in Oregon. Amazingly, biologists did not know where marbled murrelets nested until it was discovered in the 1970s along the Santa Cruz coastline that they utilized old-growth tree tops!
Their nests are generally found in forests that are greater than 200 years old, but have been found nesting in 95-100 year old mature forest stands in Oregon. They do not build their own nests, so the platforms and limbs must already be covered with a nesting material such as needles and lichen. Absence of these factors from a coastal forest may limit their distribution and habitat use. To reach their nests, marbled murrelets fly along river corridors and follow ridge lines. They approach the nest by flying below the tree canopy, as low as 2 meter, then abruptly ascend to the nest landing pad on the nest limb or a limb adjacent to the nest within 1 meter.
Each nesting pair is monogamous during nest season and incubates only one egg during the breeding season. The survival of each off-spring is essential to the continuance of the species because of the small clutch size.
Their populations have been estimated at 263,000-841,000 in North America with approximately 6,600-20,000 in Oregon. Marbled murrelets are listed as threatened species in Oregon and endangered species in California under the United States Fish and Wildlife Service. The greatest population threat to the marbled murrelet is logging of nesting habitat through development along the coast and fragmentation of habitat from logging. Fragmentation of the landscape also increases edge effects that allow more sunlight to reach below the canopy through lateral exposure. This can create a drier microclimate, making it difficult for lichens, mosses and epiphytes such as mistletoe to survive, which marbled murrelets are dependent upon for nesting.