Thriving Species and Food Web
Abundance of marine bird populations
Vital Sign Indicator
Per Square Kilometer (per sq km)

No targets are currently set for this indicator.

Scott Pearson
Contributing Partners
Last Updated
1/31/2024 9:58:55 AM
This Washington Department of Fish and Wildlife spring/summer marine bird and mammal surveys web map is an interactive tool that allows users to query and display marine bird abundance results by species (including marbled murrelet, pigeon guillemot, and rhinoceros auklet) for each survey year.

The marine bird population abundance indicator measures population abundance and trends of four bird species that breed locally or over-winter in the Puget Sound marine environment. The four species reside in Puget Sound most, if not all, of the year and include: marbled murrelet, rhinoceros auklet, pigeon guillemot, and scoters. The indicator provides an integrative view of the health of species that depend upon the Puget Sound for survival.

Vital Sign Indicator Chart

Each dot represents the estimated annual density (number of birds per km2) in Puget Sound and Strait of Juan de Fuca. The black lines are the estimated linear trends for each species across the time series. Grey band is the 95% confidence interval of the trend. Scoter = surf, white-winged, and black scoter combined. Source: Washington Department of Fish and Wildlife

These breeding and over-wintering marine birds reside in Puget Sound most, if not all, of the year and, in concert with other species and habitats, help indicate the health of Puget Sound. Marine habitats are critical to their successful reproduction, survival and to critical life history requirements such as molt and over-winter survival. As a result, the indicator provides an integrative view of the health of species that depend upon the Puget Sound for survival.

Key Vital Sign Indicator Results

Species in the marine bird indicator are displaying different abundance patterns over time.

  • In the Puget Sound and Strait of Juan de Fuca, the marbled murrelet (federally and state threatened) continues to decline by 4.6% per year during the nesting season, and declines during the winter are even greater.
  • Scoters (surf, black, and white-winged scoter species combined) continue to decline by nearly 2% per year during winter. Between 2001 and 2022 surf scoters exhibited the greatest declines, while black scoter numbers have increased since 2019.
  • Sound-wide trends for pigeon guillemot and rhinoceros auklet are stable, which is consistent with local-scale monitoring results. However, the low estimates in 2020 and 2022 for rhinoceros auklet are worth noting
Monitoring Program

Washington State Department of Fish and Wildlife Seabird Ecology Program

Data Source

Washington State Department of Fish and Wildlife Seabird Ecology Program

To help inform our breeding season trends, we also use citizen science derived information on pigeon guillemot reproduction from the Salish Sea Guillemot Network. See Methods and More Results.

The marine bird population indicator measures at-sea population abundance and trends of four bird species that nest locally or over-winter in the marine environment. The indicator includes:

  1. Spring/summer at-sea densities and trends of marbled murrelet, rhinoceros auklet and pigeon guillemot. These species are highly dependent on the marine environment of, and breed in, Puget Sound and Strait of Juan de Fuca regions.
  2. At-sea abundance and trends of scoter species that over-winter in Puget Sound and Strait of Juan de Fuca. These species are highly dependent on the marine environment of Puget Sound and the Strait of Juan de Fuca, but do not breed there.

The information used to derive the estimates for over-wintering and breeding birds come from two long-term Washington State Department of Fish and Wildlife (WDFW) survey efforts. The spring/summer surveys are boat-based and are part of the Northwest Forest Plan Effectiveness Monitoring Program for the marbled murrelet. During these surveys, observers also record other species detected such as the pigeon guillemot and rhinoceros auklet. These are boat-based, line-transect surveys using a stratified random design to produce estimates by three inland strata and for the entire U.S. portion of the Salish Sea. WDFW also conducts mid-winter surveys from an airplane that allow us to assess abundance and trends of scoters and other over-wintering species. These surveys cover the entire shoreline of the US Salish Sea, as well as a series of "offshore" transects established to estimate bird densities by both Salish Sea basins (e.g., Whidbey Basin) and depth strata.  For details on WDFW's survey methods and results, see Marine Birds Research and Monitoring and the published marbled murrelet survey methods.

The marine bird indicator was officially endorsed by the Science Panel at their April 9, 2014 meeting. The endorsement was based on a peer-reviewed report written jointly by the WDFW and the Puget Sound Partnership. The report, Marine and Terrestrial Bird Indicators for Puget Sound, develops, presents, and uses a transparent process to identify and evaluate potential indicators and ultimately recommend marine bird indicators.

The peer-review process was coordinated by the Puget Sound Partnership Science Panel in 2013. The report was finalized in April of 2014. The indicators were also endorsed by the Leadership Council in January 2014. Supplemental material to the report is linked here (Bird Indicator Supplementary material).

Critical Definitions
Interpretation of Results


Sound-wide, the density of pigeon guillemots and rhinoceros auklet has varied from year-to-year, but with no overall trend over the past 20 years. In contrast, the marbled murrelet density has declined by nearly 5% per year over the past 20 years (95% confidence interval (CI) = -7.0 – -2.9). In 2020, the population size of marbled murrelets in Puget Sound and the Strait of Juan de Fuca was estimated at 3,140 birds (95% CI = 2,030–4,590 birds). Most of the murrelet population was found in the Admiralty Inlet, San Juan Islands, and Strait of Juan de Fuca regions. The 2020 population estimates for the rhinoceros auklet and pigeon guillemot in Puget Sound and Strait of Juan de Fuca was 16,290 (95% CI = 8,670–26,120) and 6,430 (95% CI = 5,300–8,120) respectively. Although there was no apparent population trend for either the auklet or guillemot, the 2020 estimates were the lowest (auklet) and one of the lowest (guillemot) densities observed in the 20-year data series.

For scoters (surf, black, and white-winged scoter species combined), the density of birds has declined by 2% per year between 2001 and 2020. In the winter of 2020, WDFW estimates that there were 59,550 (95% CI =54,340–64,870) scoters (black, surf, & white-winged scoters) in the Salish Sea. 

More information on the distributions and densities of select marine birds can be found in the WDFW Marine Birds and Winter Seabirds web maps.

Estimates of average annual rate of population change (linear) for Puget Sound and Strait of Juan de Fuca between 2001-2020. We consider there to be evidence for a trend when the 95% confidence limits do not overlap zero.
Species Annual Rate (%) 95% Lower Confidence Limit for Annual Rate 95% Upper Confidence Limit for Annual Rate Adjusted R2 P-value
Marbled murrelet -4.96 -7.01 -2.86 0.579 0.0002
Pigeon guillemot -0.30 -1.95 1.38 0.053 0.7098
Rhinoceros auklet -0.57 -3.25 2.19 0.050 0.665
Scoters -2.02 -2.96 -1.08 0.534 0.0003












Marbled murrelet

Although the marbled murrelet spends the vast majority of its life at-sea foraging on fish, it is also dependent on forest habitats where it nests on branches of large trees. The species is federally listed as threatened and is also listed as threatened by the state of Washington. To better understand marbled murrelet decline, and to inform conservation planning to recover the species, researchers evaluated how terrestrial and marine factors influenced the distribution and abundance of the murrelet in coastal waters of the U.S. (link).

In 2016, researchers completed a 20-year review of the status and trends of murrelet populations and nesting habitat (link). They found that the murrelet populations in California and Oregon did not exhibit a population trend while the Washington population was declining. They also found that numbers of birds on the water were positively correlated with amounts and pattern (large contiguous patches) of suitable nesting habitat, and that population trend was most strongly correlated with trend in nesting habitat although marine factors also contributed. Their results suggest that conservation of suitable nesting habitat is key to murrelet conservation, but marine factors, especially factors that contribute to murrelet prey abundance, may play a role in murrelet distribution and trend. A 25-year report was recently completed and is currently in press and will be available in the coming months.

The US Navy funded annual at-sea non-breeding (September–March) murrelet monitoring in the Puget Sound region since 2012/2013 (fall through spring Salish Sea boat surveys).  Eight years of surveys suggest that non-breeding declines are much greater than breeding season declines, with an estimated annual deline of 13.5% (95% CI = -20.7 – -5.6) (link).  A manuscript exploring non-breeding trends is currently in progress and will be submitted to a journal for peer-review in 2021. 

Rhinoceros auklet

Rhinoceros auklets nest in burrows on Smith and Protection Islands in the Eastern Strait of Juan de Fuca. Protection Island, managed jointly by the U.S. Fish and Wildlife Service (primarily) and WDFW, is a globally important nesting site for rhinoceros auklets with over 35,000 occupied burrows (link). Peter Hodum (University of Puget Sound), Tom Good (NOAA Fisheries), Eric Wagner (Center for Ecosystem Sentinels, University of Washington), and Scott Pearson (WDFW) have monitored the colony on Protection Island since 2006.

Prior to a highly anomalous breeding season in 2016, rhinoceros auklet focal breeding parameters, including burrow occupancy (the proportion of burrows that were reproductively active), hatching success and fledging success, exhibited little inter-annual variability. However, fledging success in 2016 was the lowest recorded in our time series, as a consequence of a large-scale adult mortality that led to fewer adults able to provision their chicks to fledging. Fledging success in 2019 (0.86) was slightly higher than the long-term mean value of 0.79. Burrow occupancy in 2019 (0.73) returned to the long-term mean of 0.72 following depressed rates in 2017 and 2018, presumably as a consequence of the 2016 mortality event. Hatching success, unaffected throughout the anomalous seasons, continued to be consistent in 2019 (0.89 vs. long-term mean of 0.86). Nestling provisioning on Protection Island, as measured by fish per bill load and bill load weight, was comparable to long-term values in all three years (2017–2019) following the 2016 perturbation. The composition of dominant fish prey species, predominantly Pacific sand lance (Ammodytes personatus), did not vary between years. The return in 2019 of burrow occupancy to the long-term average coupled with hatching and fledging success values comparable to long-term values and average nestling provisioning suggest that the Rhinoceros Auklet breeding population on Protection Island has recovered from the multi-year impacts of the 2016 breeding failure.

Top Panel: Proportion of Protection Island rhinoceros auklet burrows that were occupied (an egg was laid); Middle Panel: Of the occupied nests, the proportion of eggs that hatched; and Bottom Panel: the proportion of chicks that reached fledging age (mostly feathered).   

Source: Washington Department of Fish and Wildlife & University of Puget Sound


Pigeon guillemot

Pigeon guillemots nest most commonly on cliff faces, crevices among boulders and occasionally in piles of driftwood, or in man-made structures such as wharfs, pipes and bridges (e.g. Hood Canal Bridge). Ongoing citizen-science monitoring by residents of Whidbey Island (2008-2020) indicates lower reproductive success (burrows with chicks) for the past 3-4 years, which could ultimately influence future population trends. Interestingly, the data also suggest a change in chick diet in recent years with a decrease in gunnels (family Pholidae) provided to chicks in 2018 and 2019 and an increase in sculpin (Cottoidea) provisioning since 2016. These diet and reproductive changes warrant additional study and observation to assess their ultimate impact on local populations.  Note that there is now an active network of citizen science groups monitoring guillemots throughout the Sound and future Vital Sign updates will include data from the entire Nework, which includes citizen science data from Whidbey Island, South Sound, Olympic Penninsula, Kitsap Penninsula, and Vashon and Maury islands.

Source: Salish Sea Guillemot Network



Three scoter species (surf, black and white-winged) over-winter in the Salish Sea. They spend about eight months of the year in this region, with some non-breeding individuals here year-round. While over-wintering, they forage, replace their feathers and put on weight needed to successfully reproduce in high arctic lakes in the summer. Research by Vilchis et al. (2015) indicates that over-wintering species were three times more likely to exhibit population declines in the Salish Sea than local breeders; scoters declined in 9% of the 67 depth/basin strata evaluated between 1994 and 2010. In general, Vilchis et al (2015) found that alcids (species like the marbled murrelet and common murre) and sea ducks (species like the scoters) dominated the over-wintering bird community during the 1990s, whereas non-diving bird species and diving species with diverse diets dominated the wintering bird community in the 2000s. Recent work by Ethier et al. (2020) the British Columbia Coastal Waterbird Survey examining 20 years of Salish Sea and coastal marine bird trends also found significant declines for all three scoter species in the Salish Sea but no significant trends for the B.C. coast. This research suggests that benthic forage species, like scoters, are demonstrating the steepest 20-year declines among all species groups examined.

Please see Interpretation of Results


Vilchis LI, Johnson CK, Evenson JR, Pearson SF, Barry KL, Davidson P, Raphael MG, Gaydos JK.2015. Assessing ecological correlates of marine bird declines to inform marine conservation. Conservation Biology 29(1): 154-163. PDF

Ethier, D., P. Davidson, G. H. Sorenson, K. L. Barry, K. Devitt, C. B. Jardine, D. Lepage, and D. W. Bradley. 2020. Twenty years of coastal waterbird trends suggest regional patterns of environmental pressure in British Columbia, Canada. Avian Conservation and Ecology 15(2):20. PDF


Overview of the birds and mammals that depend upon the Salish Sea

Background information on marine bird habitats in Washington

Guidance and considerations for setting marine bird vital sign targets 


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Reporting Guidance
Reporting Instructions

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