Marbled Murrelets are difficult to monitor during the breeding season because they nest in coastal old-growth forest, are solitary, and difficult to locate. At-sea surveys in Clayoquot Sound, British Columbia, suggest that abundance may have declined by 40% between 1982 and 1993 in that region, despite the fact that the area is largely protected from forest harvesting (Kelson et al. 1995). Models of demographic parameters in the 1990s also indicate the potential for large decreases in population size (Beissinger 1995). Because Marbled Murrelets are often in nearshore waters throughout the year, counts in winter offer another source of information on their population status. Christmas Bird Count data from British Columbia suggest a large decrease in the wintering population relative to 1970 (Meehan et al. 2018), and though the trend is moderately precise, the number of count circles included in the analysis is low (~20/year). Interestingly, Alaska, Oregon, and California are all showing increases relative to 1970, while Washington, which is adjacent to British Columbia, is also showing a large decrease (Meehan et al. 2018). The British Columbia Coastal Waterbird Survey, which is largely restricted to southern British Columbia, suggests that the abundance of Marbled Murrelets in the surveyed area has increased moderately since 1999, though the trend has low precision and shows large fluctuations, which lowers the survey's reliability. Analyses of radar monitoring counts from 1996-2013 within the 6 Marbled Murrelet Conservation Regions in British Columbia identified by the Recovery Team indicate a -1.6% per year decline for the province as a whole, with significant declines on the East Coast of Vancouver Island and the Southern Mainland Coast (Bertram et al. 2015). This analysis is currently being updated to include more recent radar monitoring data (up to 2018); preliminary results indicate a declining trend of -2.8% per year, with all six conservation regions showing a negative trend (K. Woo, ECCC, pers. comm.). Taking all of these disparate sources into account, and because the species is an old-growth specialist, the population likely remains well below the levels seen in the 1970s. However, the reliability of this assessment is considered to be low due to the disagreement among the survey and their current limitations. A quantitative population goal remains to be determined, but the species is considered to be below the lowest acceptable levels until it is de-listed under the Species at Risk Act.
Additional information on: British Columbia Coastal Waterbird Survey
