Pigeon Guillemots on Whidbey Island, Washington: A Six-Year Monitoring Study
2016
Bishop, Emily | Rosling, Govinda | Kind, Phyllis | Wood, Frances
Collecting long-term population trend data on indicator species contributes to our understanding of overall ecosystem health. The Pigeon Guillemot, a burrow-nesting piscivore, was identified as one of many indicators of health in Puget Sound, Washington. We observed the local guillemot population size, burrow occupancy, chick diet composition (identified as single fish carried in adult bills), and prey delivery rates to chicks on Whidbey Island, WA, between 2009 and 2014. Observations were conducted by trained volunteers from the Whidbey Audubon Society and the former Island County Beach Watchers (now Sound Water Stewards) who counted adults, verified burrow occupancy, and recorded prey delivery frequency and composition. Using the maximum counts across all Whidbey Island colonies, the index of abundance observed annually was an average of 991 individuals. A mean of 240 occupied burrows were observed each year. The peak rate of prey delivery occurred between the weeks of 12 July and 2 August, annually. Types of delivered prey consisted of 57.6% gunnel or prickleback (Pholidae or Stichaeidae), 25.6% sculpin (Cottidae), and 16.5% other or unknown prey. These data serve as a diet and reproductive baseline for assessing changes over time.
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