Paper reports on study of marine habitat selection by marbled murrelets

The marbled murrelet is a federally threatened bird that forages at sea and uses coastal, old-growth coniferous forests for nesting. Multiple studies have indicated continuing declines in the murrelet’s population. While conservation efforts have largely focused on the need for large trees to provide nesting platforms, it is unclear whether continued declines are due to losses in nesting habitat or changes in the marine environment.

To assist in gaining a better understanding of murrelet use of foraging habitat, NCASI supported a study by the U.S. Forest Service Pacific Northwest Research Station on marine habitat selection by individually tagged marbled murrelets.

Researchers found that marbled murrelets moved much greater distances in coastal waters offshore from Washington State than has been shown in more northerly portions of their range. Murrelets displayed a preference for marine habitats near certain terrestrial features such as areas with a lower footprint of human activity and a higher portion of landscape classified as suitable for nesting. Findings also suggest that marine habitat use may be related to factors in the marine environment assumed to be correlated with prey abundance, such as lower surface water temperature and higher level of chlorophyll a.

The abstract for the paper follows.

“The marbled murrelet (Brachyramphus marmoratus) is a declining seabird that is well-known for nesting in coastal old-growth forests in the Pacific Northwest. Most studies of habitat selection have focused on modeling terrestrial nesting habitat even though marine habitat is believed to be a major contributor to population declines in some regions. To address this information gap, we conducted a 5-year study of marine resource selection by murrelets in Washington, which contains a population experiencing the steepest documented declines and where marine habitat is believed to be compromised. Across five years we tracked 157 radio-tagged murrelets during the breeding season (May to August), and used discrete choice models to examine habitat selection. Using an information theoretic approach, our global model had the most support, suggesting that murrelet resource selection at-sea is affected by many factors, both terrestrial and marine. Locations with higher amounts of nesting habitat (β = 21.49, P < 0.001) that were closer to shore (β = -0.0007, P < 0.001) and in cool waters (β = -0.2026, P < 0.001) with low footprint (β = -0.0087, P < 0.001) had higher probabilities of use. While past conservation efforts have focused on protecting terrestrial nesting habitat, we echo many past studies calling for future efforts to protect marine habitat for murrelets, as the current emphasis on terrestrial habitat alone may be insufficient for conserving populations. In particular, marine areas in close proximity to old-growth nesting habitat appear important for murrelets during the breeding season and should be priorities for protection.” 

Reference 

Lorenz, T.J., M.G. Raphael, T. D. Bloxton, Jr. 2016. Marine habitat selection by marbled murrelets (Brachyramphus marmoratus) during the breeding season. PLoS ONE 11(9):e0162670. https://dx.doi.org/10.1371/journal.pone.0162670