Monitoring Kittlitz’s and marbled murrelets in Glacier Bay National Park and Preserve: 2014 annual report

Sergeant, Christopher; Johnson, William; Schaefer, Anne; Hoekman, Steven

Since 2009, the National Park Service’s Southeast Alaska Inventory and Monitoring Network (SEAN) has monitored population abundance and spatial distribution of Kittlitz's (KIMU) and marbled murrelets (MAMU) in Glacier Bay National Park and Preserve, an important summer residence for both species. Monitoring program design focuses on KIMU, with secondary consideration of MAMU. The SEAN uses boat-based line transect surveys to estimate species-specific, on-water density and abundance of murrelets, accounting for detection probability and unidentified murrelets. We surveyed 246.5 km on 45 transects from 7-16 July 2014 across the 1,170 km2 survey area in Glacier Bay proper. We estimated an abundance of 10,422 KIMU (SE = 1,522) and 41,474 MAMU (SE = 3,988). From 2009 to 2014, KIMU abundance estimates have ranged from 7,210 to 16,469 (6-year average = 11,335) with annual changes of -56% to 120%, while MAMU have ranged from 28,978 to 84,428 (6-year average = 57,154) with annual changes of -51% to 113%. Such large variation was very unlikely to reflect solely intrinsic population dynamics.This season, in cooperation with S. Hoekman (Wild Ginger Consulting), the SEAN participated in field trials assessing multi-observer methods to reliably estimate species identification error rates during surveys. The results of this work will be reported in a future peer-reviewed publication.During July 2013, SEAN staff and volunteers participated in a field experiment designed to evaluate the magnitude of KIMU versus MAMU identification error among six observers of differing experience levels and under a suite of environmental conditions. The results were applied to measure potential bias in abundance estimates induced from varying identification error rates. The average misidentification rate was low, with an average probability of 0.036 (SE = 0.004) across all observers. Observer experience was the main driver of variation in identification error rates, with more experienced observers making fewer errors. Therefore, these results emphasize the importance of conducting consistent, rigorous observer training before and during abundance surveys to increase confidence in species identification and precision in abundance estimates of both KIMU and MAMU. 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: 2014 annual report

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