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 (
x = 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;
x = 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.

Citation

Lorenz, Teresa J.; Raphael, Martin G.; Bloxton, Thomas D.; Cunningham, Patrick G. 2016. Low breeding propensity and wide-ranging movements by marbled murrelets in Washington. The Journal of Wildlife Management. 81(2): 306-321.