Volume 44, No. 2

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Ancient Murrelet Synthliboramphus antiquus colony attendance at Langara Island assessed using observer counts and radar in relation to time and environmental conditions


1Centre for Wildlife Ecology, Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC  V5A 1S6, Canada
2Current address: Department of Biological Sciences, University of New Brunswick, P.O. Box 5050, Saint John, NB  E2L 4L5, Canada (


MAJOR, H. 2016. Ancient Murrelet Synthliboramphus antiquus colony attendance at Langara Island assessed using observer counts and radar in relation to time and environmental conditions. Marine Ornithology 44: 233 - 240

Received 10 June 2016, accepted 26 July 2016

Date Published: 2016/10/15
Date Online: 2017/02/28
Key words: Ancient Murrelet, Synthliboramphus antiquus, Langara Island, marine radar, colony attendance, weather, light


The decision to attend a colony on any given day or night is arguably the result of a trade-off between survival and reproductive success. It is often difficult to study this trade-off, as monitoring patterns of colony attendance for nocturnal burrow-nesting seabirds is challenging. Here, I 1) examined the effectiveness of monitoring Ancient Murrelet colony arrivals using marine radar, and 2) evaluated differences in colony attendance behavior in relation to time, light, and weather. I found a strong correlation between the number of Ancient Murrelets counted by observers in the colony and the number of radar targets counted, with estimated radar target counts being ~95 times higher than observer counts. My hypothesis that patterns of colony attendance are related to environmental conditions (i.e. light and weather) and that this relationship changes with time after sunset was supported. The top supported model included interactions between time after sunset and light and weather variables, suggesting that they were important predictors of colony arrivals. Contrary to my prediction, results suggest that light conditions (moon absence and cloud cover) and wave height were most important for individuals arriving three hours after sunset (when >75% of arrivals would be breeders). Assuming the majority of birds arriving early in the night are breeders and those arriving late in the night are non-breeders, these results suggest differences in patterns of colony attendance that may be attributed to age and/or breeding status.


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