Threatened and Endangered Species - Status Reports
Date Published: October 2016
Number of Pages: 36
Author(s): Steven M. Desimone
The Marbled Murrelet (Brachyramphus marmoratus) is a small seabird that inhabits nearshore marine environment in western North America. The distribution of murrelets in Washington includes the southern Salish Sea and the outer coast. The species was listed as threatened under the U.S. Endangered Species Act in 1992 in Washington, Oregon and California, primarily due to loss of old forest nesting habitat from commercial timber harvesting and mortality associated with net fisheries and oil spills, and was subsequently listed by the Washington Fish and Wildlife Commission as threatened in 1993. In 1997, Washington enacted State Forest Practices Rules to address impacts to murrelets from timber management on non-federal lands. Marbled Murrelets forage in the marine environment and may fly up to 55 miles inland where they nest and rear a single young on large tree limbs in mature and old conifer forests. Murrelets prey primarily on a variety of forage fishes, and sometimes on larger zooplankton. They exhibit strong site fidelity to nesting areas, appear to nest in alternate years, on average, and have a naturally low reproductive rate.
In Washington, since 1993 nesting habitat losses due to timber harvest have been substantial, with an estimated 30% cumulative loss on nonfederal lands. For all Washington land ownerships combined, the net loss was 13.3%, an average annual rate of -0.7% per year. At-sea population monitoring from 2001 to 2015 indicated a 4.4% decline in the murrelet population annually, which represents a 44% reduction since 2001. The 2015 population estimate for Washington is about 7,500 birds.
Sustained low juvenile recruitment has been identified as a main cause of the decline, but cumulative effects from threats on individuals and populations is not fully known. Vital demographic data are lacking, such as adult and post-fledging survival, and reproductive and emigration rates. Nest success is influenced by both terrestrial and marine factors, such as the availability of nesting sites and the amount and fragmentation of nesting habitat, which influences nest predation risk by avian predators such as jays, crows, and ravens. A 20% nest success rate in Washington for the period 2004-2008 was attributed to nestling starvation or adults abandoning eggs before completing incubation, suggesting low prey availability. Human marine activities appear to influence murrelet abundance and distribution in the Salish Sea. Declines in populations of forage fish species such as herring and anchovy subsequently resulted in an increased use of lower trophic level, less calorie-rich food sources (invertebrates). Ultimately, these changes to the marine food web may have influenced reproductive output. Federal and state landscape plans, and Forest Practices Rules implemented to help stem the loss of higher quality nesting habitat have been beneficial, but have not led to recovery goals being met.
The magnitude of the population decline indicates that the status of the Marbled Murrelet in Washington has become more imperiled since state listing in 1993. Without solutions that can effectively address these concerns in the short-term, it is likely the Marbled Murrelet could become functionally extirpated in Washington within the next several decades. Therefore, our recommendation is to list the Marbled Murrelet as a state endangered species in Washington.
Desimone, S. M. 2016. Periodic status review for the Marbled Murrelet in Washington. Washington Department of Fish and Wildlife, Olympia, Washington. 28+iii pp.
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