Pigeon Guillemot Nesting Behavior on San Juan Island, Washington

Abstract

Pigeon Guillemots (Cepphus columba) are seabirds native to the west coast of North America and forage on the sea floor for benthic fish. The variety in their nesting sites makes them prime subjects for studying the effects that urbanization has on their nesting behavior and provisioning. We asked; how does nesting behavior differ between dock and cliff nesters and how does the presence of humans affect the duration of adults delivering fish to their chicks? We used behavioral observations to record the types of fish being brought to the nest, approaches to the nest and where the bird spent most of their time at the sites. For eight weeks, we surveyed two field sites on San Juan Island, Washington, where we watched two cliff nests and one dock nest. To determine how human presence affects length of delivery, we ran two trials: a control in which there was no human presence near the nesting site, and an experimental in which we placed one of the researchers below the nest. We recorded time in seconds that the bird sat in the water with the fish in its mouth before entering the nest. Between the control and experimental of the cliff nesters, we found that the delivery time for the experimental trial was significantly higher than the control (p <.0001). The dock nesters also showed relatively high delivery duration. There were also qualitative differences in the approaches to the nests at the two sites, including approach behavior and the prevalence of incomplete deliveries when a bird abandoned the fish in the presence of high levels of humans. The results of this experiment provided an interesting insight into how human activity may influence Pigeon Guillemot behavior and provides a foundation for future studies to expand the sample size and examine other aspects of this influence. Future experiments to build on this data could explore the difference in survival rate of chicks between sites, which could show us a direct relationship between urbanization and the decrease of population of the Pigeon Guillemot in the San Juan Islands.