Monitoring Kittlitz's and marbled murrelets in Glacier Bay National Park and preserve: 2010 annual report

Hoekman, Steven; Moynahan, Brendan; Lindberg, Mark

The Southeast Alaska Network (SEAN) has targeted Kittlitz's murrelets (Brachyramphus brevirostris) in Glacier Bay National Park and Preserve for long-term monitoring based on concerns arising from evidence of global and local populations declines in this rare seabird. In 2009, we implemented boat-based line transect surveys in Glacier Bay proper (hereafter "Glacier Bay") to address these challenges, with an emphasis on testing efficacy of novel survey and analytic methods. Based on these results, we retained use of line transect methods, shore-to-shore transect orientation, spatially-balanced sampling, and analytic methods accounting for incomplete detection and species identification. We further refined methods for 2010 by preferring 2 over 1 survey observers, allocating sampling effort via unequal probability sampling, introducing a local variance estimator for encounter rates, implementing zigzag rather than linear transects in enclosed waters, and increasing sampling coverage of Glacier Bay to include selected non-motorized and critical habitat areas. Our objectives for this report were to 1) describe changes in methods, 2) estimate abundance of Kittlitz's murrelets, and secondarily of marbled murrelets (B. marmoratus), in Glacier Bay during July 2010, and 3) place our 2009 and 2010 abundance estimates in meaningful context relative to other recent estimates for Glacier Bay.We estimated an abundance of 14,503 ± 1,479 (x ± SE) Kittlitz's and 67,259 ± 5,854 marbled murrelets in Glacier Bay during July 2010. Abundance of Kittlitz's murrelets in 2010 was similar to 2009, but more than doubled for marbled Murrelets. We found the largest concentrations of both species in open waters in the mid- to lower portions of the main Bay, a distribution that was atypical for Kittlitz's murrelets, which are frequently associated with glacially-influenced habitats in the upper fjords of Glacier Bay. Please refer to the synthesis and program review report for monitoring of Kittlitz's murrelets in Glacier Bay National Park and Preserve which contains important findings that may affect the interpretation of abundance estimates (Hoekman, S. T. 2019. Kittlitz’s murrelet monitoring in Glacier Bay National Park and Preserve 2010–2018: Synthesis and program review. Natural Resource Report NPS/SEAN/NRR—2019/1957. National Park Service, Fort Collins, Colorado, https://irma.nps.gov/DataStore/Reference/Profile/2265288). The report summarizes the results of murrelet monitoring from 2010-2018, assesses monitoring performance and capacity to meet protocol objectives, and provides recommendations for potential enhancements to the monitoring protocol. Hoekman (2019) identifies misidentification and partial identification of murrelets which can bias abundance estimation and spatially-explicit density estimates, particularly for rare species, such as Kittlitz’s murrelets.

Monitoring Kittlitz's and marbled murrelets in Glacier Bay National Park and preserve: 2010 annual report

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