Marbled murrelets were once considered as numerous off our coast. Loss of suitable-age forest habitat for nesting is considered the single biggest concern in seeking to stabilize populations.
The marbled murrelet (Brachyramphus marmoratus) is a small sea bird about the size of a robin. It is the only tree-nesting bird in the Alcid family, which also includes puffins, guillemots and murres.
Marbled murrelets spend most of their time at sea feeding on fish, but nest inland in mature and old growth coastal rainforests. Murrelets do not build nests but rather rely on large tree branches with natural depressions and moss in which to lay their egg. Only mature and old growth conifers have branches large enough to accommodate their nesting needs.
Nesting habitat consists of large core areas of old-growth or mature forest with:
- Low amounts of edge habitat,
- Reduced habitat fragmentation,
- Proximity to the marine environment, and
- Forests that are increasing in stand age and height.
The birds do not nest every year. When marbled murrelet nesting occurs, it takes place between mid-April and September. The birds have high site fidelity, returning to the same tree or stand to nest. The female lays one egg and the male and female incubate the egg in shifts while the other bird feeds in the ocean. Typically, they switch shifts at dawn or dusk. Predominately due to the risk of predation, marbled murrelets tend to be very secretive when entering and leaving their nest sites, which makes it difficult to detect nesting birds.
The primary reason marbled murrelets are protected under the Endangered Species Act (ESA) is because of extensive logging of mature and old-growth forest over the past 150 years. Extensive logging has resulted in the fragmentation of murrelet nesting habitat, which affects population viability and size, and can lead to displacement, fewer nesting attempts, failure to breed, reduced fecundity, reduced nest abundance, lower nest success, increased predation and parasitism rates, crowding in remaining patches, and reductions in adult survival.
Additionally, habitat loss can lead to the increased risk of predation from corvids, like jays and ravens, which is a significant threat to murrelet populations. Significant murrelet nesting failure is due to predation from corvids who can fly into the edges of older forests. Murrelets need large interior forests to avoid nest predation.
Species Fact Sheet
A seabird in the Alcid family, the marbled murrelet is related to the puffin but is smaller and lacks the colorful bill and headdress of that bird. Alcids are a family of diving seabirds well-represented by 16 species in the eastern north Pacific. Members of the group are sometimes referred to as northern penguins because many sport striking black and white plumage and all “fly” underwater using their wings when foraging.
Marbled murrelets are a chunky, robin-sized bird with a short, thick neck, short tail and long, narrow wings. In summer, marbled murrelets are dark brown above and heavily mottled below. In winter and in juvenile plumage they are white below (smudgy in juveniles) with dark gray to black head and back.
Range and Habitat
Marbled murrelets are found in near-shore waters from the Aleutian Islands to Southern California. They frequent quiet marine waters such as the Inside Passage of British Columbia and Southeast Alaska or bays and coves along the open coast. Recent debate has focused on whether or not its broad range encompasses distinct populations or should be considered as one population.
Marbled murrelets are often seen in pairs on the water. When approached by ship they typically spread their wings slightly and dive, or lift off from the water and accelerate away with rapid wing beats as they skim just above the surface. In the latter instance they begin flight with feet spread wide for additional lift, briefly exposing their bright white upper-tail coverts. As they gain speed and streamline their posture the feet are tucked in and the white coverts “zip” closed. Flight is direct and fast, and the birds have been clocked at 100 mph.
In the far north and west parts of their range, where there are no trees, marbled murrelets nest on the ground on cliffs or steep hillsides. However, throughout most of their range they are unique among seabirds in that they nest in the tall, old-growth trees of the coastal rainforest where they find moss-draped branches of sufficient size that offer a platform for their single egg. This nesting behavior of the marbled murrelet was unknown by ornithologists until 1974. Nest sites are situated singly, high in the forest canopy, as much as 200 feet above the ground. Several pairs may utilize a suitable grove of large trees. Nesting has been documented over 30 miles inland, a distance the adults must cover hundreds of times during incubation and feeding of the chick. When the chick fledges at approximately 35 days old it leaves its tree-top home and flies to the ocean under the cover of darkness, to take up a life at sea alone.
Birds of Oregon: A General Reference. Edited by Marshall, Hunter, Contreras
Lives of North American Birds. Kaufman
Rare Bird, Maria Mudd Ruth