Data Zone
Justification of Red List category
This species is still abundant, but it is treated as Endangered because its population is estimated to have undergone a very rapid reduction, especially in the southern portion of its range, which is expected to continue, owing to a variety of threats.
Population justification
COSEWIC (2012) estimated the total population to number 358,200-417,500 individuals, rounded here to 350,000-420,000 individuals, based on 271,000 individuals in Alaska (Piatt et al. 2007), 72,600-125,600 in British Columbia (Bertram et al. 2007), and 15,400-23,900 individuals in Washington, Oregon and California (Falxa et al. 2014, Falxa and Raphael 2016). This range equates to 238,800-278,300 mature individuals, rounded here to 240,000-280,000. The latest estimate from Partners in Flight (2019) suggests a population of mature individuals of 260,000.
Trend justification
The population was estimated to have declined by c.11% in 2000-2013 in Washington, Oregon, and California (Falxa et al. 2014), with a 50% decrease in Alaska in 1972-1992 (Piatt and Naslund 1995). Although population declines in Oregon and California are reported to have been stabilising in recent years (Falxa and Raphael 2016, A. Burger in litt. 2020), declines have continued in Washington State with adult Murrelet densities declining on the shores of the San Juan Islands from 11.16 to 5.76 individuals/km2 between 1995-2012, mirroring declines witnessed by large-scale at-sea surveys (Lorenz and Raphael 2018). Population declines in Washington are currently estimated at ~4.6% per year (Falxa and Raphael 2016). At-sea surveys over the past 25 years in British Columbia suggest declines of c.1% per year (Piatt et al. 2006), although radar surveys suggest the population may have been relatively stable since 1999 with declines in some regions of British Columbia (COSEWIC 2012, Bertram et al. 2015). Availability of nesting habitat in British Columbia, which is strongly correlated with local breeding populations (Burger 2001, Burger et al. 2004), has declined by 22% between 1978 and 2008, and is continuing (COSEWIC 2012). Overall declines are suspected to be very rapid and on-going due to very low measured productivity rates.
Brachyramphus marmoratus occurs in the U.S.A. and Canada in California, Oregon, Washington, British Columbia, south-east Alaska, Prince William Sound, Kenai Peninsula, Lower Cook Inlet, Barren Islands, Afognak and Kodiak Islands, the Alaska Peninsula and the Aleutians locally to Andreanof and Near Islands (Gaston and Jones 1998). In Alaska (70% of the population), historical estimates place the population at c. 750,000 individuals, though when trend estimates are applied to this figure it gives an estimated 2006 population of c. 271,000 individuals (Piatt et al. 2007). The British Columbia population was previously thought to be c. 54,000 - 92,500 (Piatt et al. 2006) but extrapolations from recent radar counts suggest the population may in fact be c. 72,600-125,600 birds (COSEWIC 2012). This higher estimate is likely due to differences in survey methodology as opposed to a genuine population increase. The population in Washington, Oregon and California is estimated at 15,400-23,900 individuals (Falxa et al. 2014, Falxa and Raphael 2016). The greatest historical decreases have occurred in Washington, Oregon and California (A. Burger in litt. 2012, Falxa and Raphael 2016). Declines are also reported in British Columbia and south-east Alaska (Perry 1995). Trend analyses conducted during 2000-2013 suggest a decline of c.11% over the period in Washington, Oregon and California (Falxa et al. 2014, Falxa and Raphael 2016), and a decrease of c.70% in Alaska from the 1980s to 2006 (Piatt et al. 2006). At-sea surveys over the past 25 years in British Columbia suggest declines of c.1% per year (Piatt et al. 2006), although radar surveys suggest the population may have been relatively stable since 1999 with declines in some regions of British Columbia (COSEWIC 2012, Bertram et al. 2015). Availability of nesting habitat in British Columbia, which is strongly correlated with local breeding populations (Burger 2001, Burger et al. 2004), has declined by 22% between 1978 and 2008, and is continuing (COSEWIC 2012).
It nests in old-growth and older-aged trees (up to 60 km inland) and on the ground (only in northerm part of range) (Piatt and Ford 1993, Gaston and Jones 1998, Burger 2002, McShane et al. 2004, Piatt et al. 2006, Barbaree et al. 2014), with the breeding season stretching between March and September in California, April and September in British Columbia, and May and September in Alaska (Piatt et al. 2006). Forest areas with multiple canopy layers and high moss abundance are strongly preferred. Research in British Columbia shows that in areas where forest habitat is relatively plentiful the species seldom re-use the same trees as nest sites, whereas in areas where logging has reduced old-growth there is a higher proportion of nest tree re-use (Burger et al. 2009). The species has been shown to suffer increased predation and disturbance at forest edges adjacent to recently cleared areas, compared with forest edges adjacent to regenerating or riparian areas (Malt and Lank 2009). Multiple radar and modelling studies have shown a significant correlation between numbers of birds entering watersheds and the areas of suitable forest habitat within those watersheds (Burger 2002, Burger et al. 2004, Raphael et al. 2011). Breeding is mid-March to early September in California, but more compressed further north (Hamer and Nelson 1995a, b, Gaston and Jones 1998, Burger 2002). The diet is sandlance, herring, other small schooling fish and, in winter, invertebrates (Gaston and Jones 1998, Piatt et al. 2006). Chicks are generally fed large subadult or adult prey rather than juveniles or larvae (Piatt et al. 2006). It feeds in near-shore habitats up to 1.4 km offshore, in sheltered waters, lagoons and sometimes inland lakes (Carter 1986, Hunt 1995, Gaston and Jones 1998, Burger 2002, Hebert and Golightly 2008). The effect of marine attributes on murrelet productivity varies from increasing density and productivity estimates with increasing sea surface temperature in the San Juan Archipelago, Washington (1995-2007; Raphael and Bloxton 2008), to decreasing reproductive efforts with warmer sea-surface temperatures in California (Bigger and Chinnici 2008). Sea-surface temperatures and other marine attributes explained little of the variation in murrelet distribution and abundance compared to the amount and cohesion of forest nesting habitat (Raphael et al. 2015). Daily movements to feeding areas can be up to 250 km in exceptional cases (Whitworth et al. 2000), but are normally about 30 km (Burger 2002, Piatt et al. 2006). Radio-marked birds from Redwood Creek in North California moved a maximum average distance of 99 km alongshore, with males travelling further than females, and non-breeding males travelling further than breeding males, perhaps in search of mates or nesting habitats. Average home range size was 505 km2, again being greater for males than females (Hebert and Golightly 2008). Individuals exhibit plasticity in their foraging behaviour, foraging closer to shore and increasing dive rates during nesting (Peery et al. 2009). Marbled Murrelets most often forage in pairs (Piatt et al. 2006). Individuals in the northern part of its range may travel south during the non-breeding season, a movement which likely reflects the availability of prey (Piatt et al. 2006).
Loss of nesting habitat is strongly linked to population decline through most of the species’s range (Burger 2002, Piatt et al. 2006, Burger and Waterhouse 2009). The massive (85–90%) reduction in old-growth forest (nesting habitat) in California, Oregon, Washington and British Columbia due to logging likely drove the decline and fragmentation of Murrelet populations in these regions (Sealy and Carter 1984, Rodway et al. 1992, Stein and Miller 1992). Forest loss and fragmentation continues, with the area of 'higher-suitability' habitat declining by 12% between 1993 and 2012 (c.18% in three generations), most of which occurred on non-federal land (Falxa and Raphael 2016). In accordance, Long et al. (2011) estimated that suitable nesting habitat declined by 20-22% between 1978 and 2008 in British Columbia. Multiple radar studies have shown that when breeding habitat is reduced by logging, the birds do not show ability to relocate to remaining forest patches in higher densities, but instead suffer population declines (Burger 2001, Burger et al. 2004, Raphael et al. 2006), and there is strong support for habitat loss due to logging being the primary driving mechanism for the population decline (Burger 2002). A linked threat is the elevated predation pressures at range margins. Murrelet distribution and abundance is directly correlated to the amount and cohesion of forest nesting habitat (Raphael et al. 2015) and the species has been found to suffer increased corvid (jays and ravens) predation and disturbance at forest edges adjacent to recently cleared areas (Burger 2002, Malt and Lank 2009). Other experiments found that the rate of predation of artificial nests on the Olympic Peninsula was significantly correlated with corvid abundance (Miller et al. 2012).
In addition, the species is at risk from interaction with commercial fisheries, and changes in prey availability caused by the combined effects of overharvesting and climate change. In 1990, an estimated 1,468 seabirds were killed in fishing nets, 97% of which were Murrelets. Murrelet mortality was strongly associated with gill-net mortality off the Washington coast and some 3300 (2940 adult) Murrelets may drown in fish nets annually throughout their range in Alaska. Assuming a population size of 280,000 individuals, of which 70% are adult breeders, then as much as 1.5% of adult mortality may derive from bycatch. And yet, this estimate does not include mortality in set nets, pound nets or seine nets (Piatt and Naslund 1995). Intense exploitation of prey species during the last century have contributed to depleting the Murrelet’s preferred food resources, causing a shift to lower-trophic-level food items (i.e. krill, sandlance and rockfishes), which appears to have been partly responsible for poor Murrelet reproduction. The decrease in trophic level was most pronounced in pre-breeding diets, which plays a crucial role in alcid life history (Becker and Bessinger 2006). Since the collapse of the Pacific sardine populations, prey quality and abundance has declined, with lower trophic-level prey (e.g. krill) now dominating the pre-breeding diet in California (Becker and Bessinger 2006). This has resulted in a lower proportion of individuals reaching breeding condition, and therefore lower population productivity.
Climate change is likely exacerbating the reductions in food availability, through changes in sea water temperatures, composition of marine fish communities, and reduced overall fish biomass with dramatic consequences in the diet and population ecology of higher vertebrates that depend on those fish populations (Piatt and Anderson, in press). Occurrence of the species on the San Juan Islands, Washington is positively correlated with winter El Niño Southern Oscillation (ENSO) indices suggesting that species are required to use the area as a refuge due to concurrent declines in prey availability along the outer Pacific Coast in ENSO years (Lorenz and Raphael 2018). Unlike short-term phenomena, such as ENSO events, the predicted long-term shifts due to climate change represent a more pervasive and persistent change in the ecosystem and can potentially have long-term effects on Alaskan Murrelet populations (Piatt and Naslund 1995). Miller et al. (2012) attributed the 2000-2010 population decline to changes in the marine environment causing reduced availability or quality of prey (among other factors), and juvenile recruitment off Vancouver Island was significantly reduced in a year of low marine productivity and prey availability (Ronconi and Burger 2008). Climate change may also result in changes to the distribution of the coniferous forests required for nesting by the Murrelets (DellaSala et al. 2015).
Mortality due to oil pollution represents another major threat to Marbled Murrelet populations. Past spills (e.g. Apex Houston, Exxon Valdez, Nestucca and New Carissa) have cause considerable mortality in affected colonies (Piatt and Naslund 1995, Nelson 1997, Gaston and Jones 1998, Burger 2002, Titmus and Smith 2008). The 1989 Exxon Valdez event killed an estimated 8,400 Marbled Murrelets (c.3% of the Alaskan population) and the toll from chronic pollution is unknown (Piatt and Naslund 1995). Future oil spills will continue to threaten the viability of small, declining populations, especially in California, Oregon and Washington where a single large spill could potentially extirpate an entire population (Carter and Kuletz 1995). There is also strong potential for direct interaction between the species and tanker traffic along the proposed "Northern Gateway" tanker traffic routes (Bertram et al. 2016).
Owing to their coastal distribution and use of relatively sheltered marine habitats, Murrelets are more exposed to vessel activities than most other seabirds in the region. Human disturbance can disrupt foraging birds and persistent boat traffic may displace birds from important foraging areas. Carter and Kuletz (1995) found that Murrelet numbers were negatively correlated with numbers of boats and low-flying aircrafts, and presented suggestive evidence that human disturbance and traffic caused disruptions to breeding.
Conservation Actions Underway
It is Threatened in all range states and provinces except Alaska. Detailed conservation recommendations were made in 1990s (USFWS 1992, Ralph et al. 1995) with a Habitat Conservation Plan drafted in 1997 for Washington State (Wilson 2019). Federal land-use in the USA is regulated, areas for management identified and surveyed, and some temporarily removed from logging (Nelson 1997, Raphael 2006). In August 2016, the USFWS released the final determination on critical habitat for the species in the listed range and in January 2010 determined that the species still warrented protection and listing as Threatened after numerous challenges by the timber industry. USFWS initiated a status review of the species in 2008, which will also function as a 5-year status review. In Canada there has been extensive research, an updated recovery strategy (Environment Canada 2014), some (relatively minor) habitat protection under the British Columbia Forest and Range Practices Act, more extensive protection of forest habitat under various Land Use agreements and a radar monitoring plan developed by the Canadian Marbled Murrelet Recovery Team (CMMRT 2003, COSEWIC 2012). The Canadian Marbled Murrelet Recovery Team developed a Recovery Strategy to be compliant with the Canadian Species at Risk Act (Environment Canada 2014). This lays out the general strategy for population stability (population reduction between 2002 and 2032 not to exceed 30% of the 2002 population and this decline is linked to similar limited decline in available suitable nesting habitat). The essential Marine and Terrestrial Action Plans required by the Species at Risk Act have not been drafted (as of 2016) and these are not likely to be completed and implemented before 2020. Under the Canadian Recovery Strategy critical nesting habitat requiring protection is defined as 70% of the 2002 suitable nesting habitat coast-wide, with varying percentages (68-90%) in the six conservation regions in British Columbia (Environment Canada 2014).
The U.S. Department of Natural Resources (WDNR) began developing a Marbled Murrelet Long-Term Conservation Strategy in 2007 (Escene 2007); the final strategy still has not been released as of 2016. The Northwest Forest Plan (1994) is expected to ensure the protection of a large proportion of important habitats in the USA (Raphael 2006).
Extensive areas of suitable forest nesting habitat have been set aside in conservancies on the northern and central mainland and in Haida Gwaii (formerly Queen Charlotte Islands) (COSEWIC 2012). Smaller areas are being protected by other forestry and conservation measures. Overall, an estimated 35% of the 1,826,828 hectares of suitable habitat in all of British Columbia (based on the Canadian Marbled Murrelet Recovery Team modeling criteria [CMMRT 2003]) had been protected under various measures by 2011 (COSEWIC 2012). In 1998, the Exxon Valdez Trustee Council protected 179 km2 of Afognak Island (BBC Wildlife 1999 172: 23). In 2007, 1,569 ha of forested land on the Oregon Coast was acquired under conservation easement for the species (amongst others), part funded by the New Carissa oil-spill funds (Escene 2007). Between 1998 and 2002, 507 Marbled Murrelets were radio-tracked in British Columbia (Zharikov et al. 2007), during 2005-2007, 111 birds were radio-tracked at Port Snettisham, Alaska (Nelson et al. 2008), and between 2004-2008, 157 birds were radio-tagged on Olympic Peninsula, Washington to determine nesting habitat, activity patterns and distribution. A recommended protocol for surveying the species in forests was published in 2003 by PSG (Mack et al. 2003). In British Columbia standard protocols have been developed for various survey methods (RISC 2001, Manley 2006). Research has shown that habitat management at relatively fine scales may provide conservation benefits (Horton 2008) and that the species would benefit from a reduction in the amount of hard edges (recent clear-cuts) at both patch and landscape scales (Malt and Lank 2009).
Conservation Actions Proposed
Survey potential nesting habitat on all ownerships and protect all occupied sites. Collect data on the ratio of juvenile to adult birds from sites throughout the range, and monitor over time, as this is thought to be a reliable indicator of productivity (Peery et al. 2007). Research means of improving the abundance of high quality food, e.g. small fish, during the pre-breeding period. Minimise damage to fish stocks and feeding areas (RENEW Report 1999 9: 20). Conduct research on the behaviour of migrants to determine the extent to which dispersal results in gene flow and prevents declines in resident populations (Peery et al. 2010). Complete and implement the SARA-compliant Canadian Marbled Murrelet Recovery Action Plans needed to implement the Canadian Recovery Strategy (Environment Canada 2014). Protect both terrestrial nesting habitat and marine habitat throughout the species's range (Lorenz et al. 2016), create larger blocks of habitat, provide buffers and other means for minimizing edge effects and predation (K. J. Kuletz in litt. 1999, USFWS 2012). Renew the radar monitoring at British Columbia watersheds (Bertram et al. 2015), in order to track population trends and determine the effects of habitat removal (logging) and local changes in marine conditions. Move campgrounds away from old-growth areas in Californian State Parks, in order to reduce predator populations in breeding areas. Reduce oil-spills, gill-net mortality and logging (K. J. Kuletz in litt. 1999). List as Threatened in Alaska (K. J. Kuletz in litt. 1999).
25 cm. Chunky alcid. Breeding plumage is dark brown above, heavily mottled below. In winter, dark grey above and white below with white scapulars, dark marks on side of breast, dark ear-coverts and whitish eye-ring. Juvenile resembles winter adult but darker scapulars and dusky mottling below. Similar spp Kittlitz's Murrelet B. brevirostris is paler, has white outer tail feathers and shorter bill. In winter, has whiter face broken by dark eye and slight eye-stripe, nearly complete breast-band and white tips to secondaries.
Text account compilers
Fjagesund, T., Everest, J., Martin, R.
Contributors
Benstead, P., Bertram, D., Burger, A.E., Calvert, R., Derhé, M., Gilroy, J., Kuletz, K., Miller, E., Moreno, R., Nelson, K. & Piatt, J.
Recommended citation
BirdLife International (2024) Species factsheet: Marbled Murrelet Brachyramphus marmoratus. Downloaded from
https://datazone.birdlife.org/species/factsheet/marbled-murrelet-brachyramphus-marmoratus on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.