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The marbled murrelet (Brachyramphus marmoratus) is a threatened seabird that forages in nearshore marine waters but nests inland, commonly in older coniferous forests. Information on ranging behavior and breeding propensity can be useful for informing management, especially when comparisons can be made between declining or threatened populations and more stable, unthreatened populations. Over 5 years, we measured ranging behavior and breeding propensity of marbled murrelets in Washington, USA where murrelets are considered threatened. Our primary objective was to compare space use and breeding by murrelets in Washington with those from other regions and where the species is not considered threatened. We radio tracked 157 murrelets from 2004 to 2008. Median marine 95% kernel ranges were 487 km2 (truex¯=938±1,348 [SD]) and larger than those reported for non‐threatened populations in Alaska, USA in other studies. Ranges computed from minimum convex polygons (MCPs; median = 404 km2; truex¯=708±847) were on average similar to those reported for threatened populations in California, USA, although larger than those reported for Alaska. Distances traveled between consecutive marine telemetry locations were greater than reported previously in Alaska. Variation in movements in our study were not associated with oceanographic conditions although appeared greater for murrelets captured along the Pacific Coast compared to those occupying interior marine waters in the Salish Sea. Twenty individuals (12.7%) attempted to breed in our study, and we estimated breeding propensity was 13.1–20.0%. This is the lowest breeding propensity reported for a population of murrelets to date. For breeders, nest‐sea commuting distances were greater than reported previously, with 4 breeders traveling farther than the previously reported maximum of 125 km. The low breeding propensity, large marine ranges, and long nest‐sea commutes in this study may point to poor‐quality marine habitat in Washington compared to other parts of the murrelet's range. In combination with reported declines in terrestrial nesting habitat from other studies, this indicates that additional management is needed to improve murrelet breeding habitat in Washington. Future management actions should focus on improving both terrestrial and marine habitat. © 2016 The Wildlife Society.

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.

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