Low breeding propensity and wide‐ranging movements by marbled murrelets in Washington

Abstract

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.

Spatial variation in exploited metapopulations obscures risk of collapse

“…, Lorenz et al. ), and some flatfishes (Moser et al. ), exhibit restricted patterns of movement and are likely to exploit one to several major subpopulations, but generally not the entire spatial distribution of the metapopulation (stock).…”

Integrating counts, telemetry, and non‐invasive DNA data to improve demographic monitoring of an endangered species

“…For example, Lorenz and Raphael (2018) found decreasing densities of adult Marbled Murrelets (Brachyramphus marmoratus), stable juvenile densities, and stable juvenile:adult ratios over an 18-yr study. These results suggested high productivity, which seemed to conflict with a concurrent telemetry study showing low breeding propensity in adults (Lorenz et al 2017). The authors proposed four different hypotheses to explain these results, demonstrating that at times, it can seem like more data actually lead to more uncertainty about the system.…”

Squeezed by a habitat split: Warm ocean conditions and old‐forest loss interact to reduce long‐term occupancy of a threatened seabird

“…Murrelets can nest >100 km from marine foraging areas (Lorenz, Raphael, Bloxton, & Cunningham, 2017) and the energetic costs of inland commuting flights are high (Hull et al., 2001), so nesting habitat that is distant from the coastal foraging sites may result in low nest success, particularly during periods of poor ocean conditions. Thus, determining the extent to which changes in forest nesting habitat and ocean conditions drive murrelet population trends has considerable conservation and management implications in the Pacific Northwest.…”