Marbled Murrelet Life History and Facts

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Marbled Murrelet Life History
and Facts

An FOER Citizen Science Report

Sharyn Boyd Becker
Ecoforestry Management Associates

Background

The Marbled Murrelet (Brachyramphus marmoratus), sometimes called a Fog Lark, is a small robin-size sea bird that nests in dense old-growth forest, usually within 20 miles of the ocean. Murrelets probably began nesting in trees 15 million years ago, when the West Coast was forested with enormous Metasequoia (dawn redwood). However, by 1991 very little coastal old-growth forest remained, leading the U.S. Fish & Wildlife Service to list the Marbled Murrelet as Threatened under the Endangered Species Act.

Life History

Like many seabirds, murrelets live just beyond the surf, diving from the surface to seize small fish. Conversely, from late April to early August, Marbled Murrelets travel inland from their ocean habitat to nest and raise their young in mature stands of coniferous trees.

After laying a single egg, a pair of adult murrelets share incubation duties. For a month they keep their egg warm in 24 hour shifts, exchanging places at dawn each day. When their chick hatches, a parent stays with it full time for up to three days. After this brief brooding period, the parents leave their chick entirely alone, returning only to feed it.

Marbled Murrelet
in breeding plumage

For the next five weeks, the adults fly from the ocean to their chick several times a day. In every trip from the Pacific Ocean, the parent carries a fish in its beak. It waits while the chick swallows it whole before returning. Flying at twilight and before dawn, murrelets tend to follow canyons and waterways, jetting above treetop level at 65-90 mph, dropping into the tree canopy just before reaching their nest. All of these factors make it is very difficult to see murrelets, let alone find their nests. In fact, they don’t even make a nest — their egg is laid on a large mossy branch about 150 feet above the ground.

When a murrelet chick is ready to fledge, it spends the day plucking away its downy camouflage and preening its adult plumage. As dusk falls, the fledgling leaves its mossy branch and flies directly to the sea - unescorted!

Fascinating Facts:

In Oregon’s off-shore waters, there are fewer than 15,000 Marbled Murrelets today. Some estimate that less than 10% of their habitat remains.

A murrelet pair mates every other year, generally breeding for the first time at 3 years of age.

After mating, the female flies into the forest and lays her single egg.

The original nesting habitat of Marbled Murrelets has been reduced by 85%. Reduced habitat means murrelet populations are isolated, and genetic diversity is reduced.

In known murrelet nests, there has been a 72% nesting failure. 50% of these nesting failures are due to predation.

Nesting is less successful in small stands of old-growth than in large intact stands of timber.

Murrelets exhibit strong site-fidelity, often returning to the same tree the next time they nest. Some birds may not search for new sites if their site is disturbed.

Since they feed close to shore, murrelets are particularly vulnerable to oil spills.

Murrelets are negatively affected by El Nińo, which reduces their food supply.

Outside of Oregon, gillnet fisheries have a negative impact on Marbled Murrelet survival.

murrelet.jpg (13568 bytes)
murrelet feeding fish to young
ŠPaul Englemeyer