In the recent paper “Using drone imagery to obtain population data of colony-nesting seabirds to support Canada’s transition to the global Key Biodiversity Areas program” by Lalach et al. (2023), the authors used quantitative global and national thresholds to determine whether an Important Bird Area (IBA) for the Glaucous-winged Gull (Larus glaucescens) met the criteria for conversion to a Key Biodiversity Area (KBA). The threshold values used were taken from the Birds Canada IBA-KBA crosswalk database (https://kba-maps.deanrobertevans.ca/). Because national estimates of bird populations (mostly derived from Breeding Bird Survey data and resulting Partner in Flight estimates) are thought to be negatively biased in Canada, this database instead uses continental population estimates for national thresholds (Sólymos et al. 2020; D.R. Evans pers. comm). In the paper, these national thresholds were erroneously referred to as being based on national population estimates, when they are actually based on the continental estimates.

This error means that the national KBA threshold of 4,400 individuals reported in Lalach et al. (2023) is based on the continental population estimate for this species (as per the National KBA Standard Protocol for this ongoing IBA to KBA conversion) (KBA Canada Coalition 2021). This resulted in a higher threshold value than would be expected based on the actual national Glaucous-winged Gull population estimates of 47,800 individuals (Rodway et al. 2023). If the IBA-KBA crosswalk were to use this national estimate, a site with only 478 breeding individuals would trigger the National KBA criterion.