Station 8 -
Like other marine birds, this chubby little auk spends its days in the ocean feeding on small fish and zooplankton, but during the breeding season it journeys deep into the forest to nest. The daily commute back and forth from sea to nest during this time is impressive for a 225 gram1.0 ounce little bird, since marbled murrelets can nest 30 to 60 kilometers19 to 37 miles away from the coast!
Marbled murrelets do not build a nest, instead they lay a large solitary egg on a wide platform such as a large limb or deformity such as those created by mistletoe. Often these platforms have a thick bed of moss (Antitrichia) to cushion and hold the egg during incubation. The problem lies in that is not just a matter of simply finding a tree and dropping its egg…this bird is picky. Marbled murrelets in the Pacific Northwest nest only in old-growth and mature forests of conifers. They require large-diameter branches which are high enough off the ground to be safe from ground predators and in dense enough forest to be safe from crows and ravens. Small canopy gaps allow the birds to access nest limbs as they are not adept at flying in tree canopies for long distances.
The nest of a marbled murrelet was a matter of speculation for more than 170 years after the bird was first described as no nests were found until one was documented by Russian scientists in 1961 and another by scientists in the United States in 1974. Since then, on-going research has revealed more nests and many scientists are currently studying these birds.
One of the alarming findings is that these birds have been declining in recent decades. They face multiple challenges: oil spills and gill-net fisheries are a threat at sea, reduced availability of food in the ocean due to oceanographic variation affects adults and nestlings dependant upon small fish, and low survival rates of nestlings due to nest predation. But in many areas, its worst threat is nest habitat loss and fragmentation. As mature and old-growth forests disappear, so do the birds. The marbled murrelet was listed as Threatened in 1992 under the Endangered Species Act.
It is not likely that variable-density thinning will benefit marbled murrelets in the short term. However, thinning in young stands should not negatively impact the birds (as they don’t nest in young stands) and we hope that thinning and the creation of gaps will increase the future availability of the large-diameter branches and the type of stand structures favored by this fascinating bird.