| Summary: | The Kittlitzs murrelet (Brachyramphus brevirostris) is a small alcid endemic to Alaska and eastern Russia. Due to its pelagic lifestyle, researchers lack information regarding environmental conditions experienced by Kittlitzs murrelets throughout the year and how these conditions impact their physiology and vital rates. Further, unlike most seabirds, the Kittlitzs murrelet is a dispersed nester; therefore, data are limited for this species even within the breeding season. The goal of this research was to evaluate and improve the monitoring methods for the Kittlitzs murrelet throughout the year. I approached this goal from 2 different perspectives. First, I worked to clarify abundance and trend estimates that have been questioned due to uncertainty in species identification. Second, I used physiological measures to examine the relationships between stress, parental investment, breeding propensity, and environmental conditions experienced by Kittlitzs murrelets throughout the year. To address uncertainties in species identification, I conducted a field experiment to quantify misidentification and non-identification rates of Brachyramphus murrelets during abundance surveys and evaluate the impacts of covariates on each. I found that misidentification of species was rare and did not bias abundance estimates. Additionally, non-identification was common beyond observation distances of 140 m, though this depended on observer experience, murrelet behavior, and sea conditions. To understand the environmental conditions experienced by Kittlitzs murrelets throughout the year, I measured corticosterone (avian stress hormone) and prolactin (parental expression hormone) and evaluated their relationships with breeding propensity and ocean productivity metrics. Higher levels of stress during the pre-and post-breeding seasons reflected lower rates of breeding propensity in the following season. Additionally, higher stress was associated with lower sea surface temperatures during the pre-breeding season, and earlier capture dates, longer time-spans between capture and processing, and lower body mass during the late-breeding season. Prolactin positively reflected CORT during the early breeding season and sex during the late breeding season. These results emphasize the need for continued research to understand the mechanisms linking the stress physiology, foraging ecology, and breeding ecology of the Kittlitzs murrelet and other species that depend on similar resources.
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