Estimating breeding status in Atlantic puffin colonies across Newfoundland: a methodological comparison

Zabala Belenguer, Raul (2023) Estimating breeding status in Atlantic puffin colonies across Newfoundland: a methodological comparison. Masters thesis, Memorial University of Newfoundland.

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Abstract

The largest colonies of Atlantic puffins (Fratercula arctica) have been experiencing decades of declining population growth linked to poor breeding performance, particularly in the Eastern Atlantic. These trends have been revealed by the presence of colony-specific monitoring programs. Such data are fragmented and not updated for Newfoundland (Canada) colonies, the largest in the Western Atlantic. Here, I have assessed the burrow laying success, fledging success, and productivity of five colonies at different latitudes in the 2021-2022 breeding season through the establishment of permanent plots. Direct comparisons between current and historical estimates were not possible due to differences in burrow assessment methods. As a remedy, I compared detection probabilities obtained by two different methods, burrowscoping and handgrubbing, and estimated a correction factor to allow for comparisons. Inter-rater reliability of the estimates was also evaluated. My findings show that estimates can be influenced by both data collection method and double-observer, even with experienced individuals. Nevertheless, every breeding parameter remained high in all colonies included in this study, suggesting an overall healthy breeding status in Newfoundland puffin populations, even in those where no historical data are available. This makes Newfoundland colonies the largest puffin aggregation worldwide with no signs of breeding failure in this declining species.

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