1. The index of richness does not adjust for multiple habitat types occurring within each 1-km² grid cell. For each species, probability of occurrence was modeled for each habitat type, and an area-weighted average across habitat types determined for each 1 km² grid cell. An index of richness was determined by summing across species. This estimate is essentially the average of point richness throughout each 1-km² grid cell, and does not incorporate the fact that 1-km² grid cells often span multiple habitat types and thus have higher richness than any single type alone, or have higher richness due to edge effects. However, a 1-km² grid cell dominated by habitats with relatively high richness will have a higher index value than a 1-km² grid cell dominated by habitats with low richness.

2. Rare species were not included when determining the index of richness. The ABMI only models species habitat associations for species that have sufficient data to create robust models. Since the index of richness is created from the species models, the index only includes species with more than a minimum number of detections. Many rare species occur in every habitat type and thus ignoring the less common species may have little influence on the index of richness since it is standardized to a maximum of 1. On the other hand, it is possible that there are some habitat types that have a disproportionate number of rare species (e.g. possibly some wetland types) and an index of richness that does not incorporate rare species would not capture this.

3.  Spatial irregularities in sampling intensity influence the index of richness. In regions with a higher intensity of ABMI surveys, more species will have reached the minimum number of detections required for modeling, and thus more species will have been included in the index of richness. Due to access challenges, ABMI sampling intensity has been relatively low in the Rocky Mountain natural region, and in northwestern Alberta. Thus, species that are most commonly found in these regions will be less likely to have been included in the index of richness and 1-km² grid cells in these regions may underestimate actual richness.