Brachyramphus murrelets at high latitude: behavioural patterns and new methods for population monitoring

• Main Author: Cragg, Jenna Louise
• Other Authors: Burger, Alan E., Gregory, Patrick T.
• Format: Thesis
• Language: English
• Published: 2013
• Subjects: marbled murrelet; Kittliz's murrelet; Brachyramphus; population monitoring; Marine radar; Autonomous acoustic sensors; Behaviour; Alaska; Archipelago; Kodiak
• Online Access: http://hdl.handle.net/1828/4730

Developing cost-effective tools for population monitoring and research is fundamental to wildlife management programs. This is a major challenge for solitary-nesting, secretive seabirds distributed throughout remote areas of Alaska: the marbled murrelet (Brachyramphus marmoratus) and Kittlitz’s murrelet (B. brevirostris). Both species have experienced major population declines in Alaska, which is the centre of the distribution of their global populations. In 2010-2012, I tested the reliability of two new remote-sensing approaches, marine radar surveys and autonomous acoustic monitoring, to assess population size, trends and distributions of Brachyramphus murrelets in the Kodiak Archipelago. The goals were to compare new and existing assessment tools, to identify differences in spatial and temporal patterns of activity by Brachyramphus murrelets at high latitudes, and to make recommendations for integrating remote-sensing methods into existing monitoring programs. Autonomous acoustic sensors provided a reliable index of marbled murrelet abundance at fine spatial scales (2-3 ha forest stands). Detections of marbled murrelet vocalizations by acoustic sensors and human observers were not statistically different across weekly means. Because high temporal replication could be achieved at no extra cost, automated acoustic sampling provided the best seasonal resolution in patterns of murrelet activity. Radar surveys identified a prolonged (150 min) duration of pre-sunrise inland flight activity relative to lower-latitude populations, reflecting the longer duration of twilight at high latitude. A clear trend in seasonal activity, increasing from June to late July, was identified by radar, audio-visual, and acoustic surveys. The strong seasonal increase in activity detected by radar surveys appears to be an important factor to consider in planning population monitoring programs. Radar surveys could not distinguish between Kittlitz’s and marbled murrelets, but identified potentially greater frequency of inland flight by ...