Naturalist Segment: Marbled Murrelets

Words by Emma Kelsey

Live in Santa Cruz long enough and you start to feel dependent on towering redwood forests and stretches of coastline that define the Monterey Bay area. Turns out we are not the only creatures who have come to depend on this unique coastal ecosystem. The Marbled Murrelet (Brachyramphus marmoratus) is a softball-sized seabird that spends the majority of its life at sea feeding on anchovies, sardines, and other small fish. Murrelets, like most seabirds, only come to land once a year - when it is time to nest. Unlike any other seabird, Marbled Murrelets nest high up in stands of old-growth trees. During the breeding season (May through August) Murrelets fly up into the Santa Cruz mountains to lay their one egg (murrelets prefer old-growth and older second-growth trees because of the elevated “platforms” created in older trees are ideal for nesting).

Naturalists first named and described the Marbled Murrelet in 1794 (Nelson 1997). Yet by the 1960s naturalists and ornithologists still hadn’t identified where the species nested. Their nesting location was so unique that it alluded the folks who thought they were paying the closest attention Meanwhile, loggers throughout North America were so familiar with the small birds that they saw and heard flying from old-growth stands towards the oceans on foggy mornings that they had a name for them -- “fog birds” or “fog larks”. It wasn’t until 1974 that naturalists and ornithologists put two and two together and started looking to the forests for murrelet nests (Nelson 1997).

Even now that the murrelet's unique nest sites have been identified, they remain hard to study and there is much we still don’t know about the Marbled Murrelet. We do, however, know that they are in trouble as a species. Marbled Murrelets are listed as Threatened under the Endangered Species Act and are listed as Endangered by the state of California (Nelson 1997, ECOS). Logging and coastal development have limited their nesting habitat throughout their range, gillnet fishing and oil spills threaten them at sea, and even natural predators have become an increasing threat to the species (Nelson 1997).

The Santa Cruz Mountains represents the southernmost part of the Murrelets range, the species is also found up the North American coast through Alaska as well as Russia and Asia on the other side of the Pacific. Here, like in almost all parts of the murrelet's range, nesting habitat is very limited. The Santa Cruz Mountains are thought to have only 10,000 acres of old and second-growth trees, 50% of which lies within Big Basin State Park alone (Singer 2003). And within that range, other threats are present.

Birds in the Corvid family (crows, ravens, and jays) are natural predators of Murrelet eggs. Due to an increase in supplementary food and habitat brought by humans, corvid populations have skyrocketed in the Santa Cruz Mountains in recent decades. With an increase in corvid numbers, there has also been an increase in the number of murrelet eggs becoming snacks for crows, ravens, and jays. Decreasing corvid predation on murrelet eggs was identified as the most effective way in conserving the murrelet population in the Santa Cruz mountains (Perry and Henry 2010). Therefore California State Parks have taken on a Crumb Clean Commitment to try to decrease Corvid attraction to our redwood forests, especially Big Basin (CDPR). If there is less human food attracting these predators to our forests, Corvids will be less likely to also prey on murrelet eggs. This is our best shot at protecting the Marbled Murrelet population in the Santa Cruz Mountains.

So, next time you find yourself up in the beautiful Santa Cruz mountains, whether enjoying the festivities after surviving the Old Growth Classic this weekend, or going on a hike or ride with friends and family, know that you can do your part for this local endangered species by picking up after yourself and keeping it crumb clean.

References

CDPR. Crumb Clean Campaign. California Department of Parks and Recreation. http://www.parks.ca.gov/?page_id=29905. Visited August 27, 2019.

ECOS. Species Profile for Marbled Murrelet (Brachyramphus marmoratus). USFWS Environmental Conservation Online System. https://ecos.fws.gov/ecp0/profile/speciesProfile?spcode=B08C visited: August 27, 2019

Nelson, S. K. (1997). Marbled Murrelet (Brachyramphus marmoratus), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.276