Old Growth Forests Provide Protection for Marbled Murrelets

Biological Strategy

C.K. Unsworth

Physically Assemble Structure

Living systems use physical materials to create structures to serve as protection, insulation, and other purposes. These structures can be internal (within or attached to the system itself), such as cell membranes, shells, and fur. They can also be external (detached), such as nests, burrows, cocoons, or webs. Because physical materials are limited and the energy required to gather and create new structures is costly, living systems must use both conservatively. Therefore, they optimize the structures’ size, weight, and density. For example, weaver birds use two types of vegetation to create their nests: strong, a few stiff fibers and numerous thin fibers. Combined, they make a strong, yet flexible, nest. An example of an internal structure is a bird’s bone. The bone is comprised of a mineral matrix assembled to create strong cross-supports and a tubular outer surface filled with air to minimize weight.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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Marbled murrelets nest in moss-covered branches of old-growth conifers near coastal waters, requiring dense canopy cover and stable microclimates.

Introduction

The marbled murrelet (Brachyramphus marmoratus), a small seabird in the auk family, is unique among its relatives for nesting in coastal old-growth forests rather than on cliffs or in burrows. This elusive bird primarily inhabits the Pacific Northwest, where its nesting habits are closely tied to the characteristics of old-growth trees. The study Characteristics of Marbled Murrelet Nest Trees and Nesting Stands by Thomas E. Hamer and S. Kim Nelson explores the specific tree and stand features that make these forests suitable for murrelet nesting, offering insights into their critical habitat requirements.

The Strategy

Marbled murrelets depend on specific tree and forest stand features for nesting, which are critical for the survival of their young. Their nests are typically found high in the canopies of large, old-growth conifers like Douglas fir, Sitka spruce, and western hemlock. These trees provide broad, moss-covered branches capable of supporting their well-camouflaged nests, as well as the stability needed to endure high winds and heavy rain common in coastal environments.

Murrelets prefer nesting stands located near water sources, such as rivers or ocean bays, which enable efficient access to foraging grounds. The surrounding landscape, particularly the presence of contiguous old-growth stands, enhances habitat suitability by providing consistent cover and reducing fragmentation that can expose nests to predators.

The Potential

Protecting the nesting habitat of marbled murrelets can inform forest conservation strategies, emphasizing the preservation of old-growth stands and mature trees. Their preference for moss-covered branches could inspire bio-inspired designs for stable, weather-resistant platforms or structures. The murrelet’s ability to nest in high, concealed locations highlights the importance of integrating height, camouflage, and insulation into designs for secure and energy-efficient shelters. Lastly, understanding their habitat requirements can guide sustainable forestry practices and conservation planning to balance human activity with biodiversity preservation.

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Last Updated January 14, 2025

References

Report

Chapter 6: Characteristics of Marbled Murrelet Nest Trees and Nesting Stands

Forest Service, USDA | 1995 | Ralph, C. John, Hunt, George L., Jr., Raphael, Martin G., Piatt, John F., Technical Editors.

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