Predicted population cores (25%, 50% and 75%) of breeding thick-billed longspur (Rhynchophanes mccownii) based on a range-wide random forest distribution model. We summed the probability of occurrence across all pixels in the study region to generate an index of total population. We placed each grid cell prediction in the context of the study area by dividing the individual pixel probability by the total index. Starting with the highest-value pixels, we cumulatively summed the probabilities until a given threshold was met. We set 25, 50 and 75% thresholds to delineate cores as the smallest possible areas containing the highest concentrations of predicted birds.