Estimating historic ranges of extinct scavenging birds from North America during the late Pleistocene using co-occurrence data from the fossil record

Abstract: The aim of my study was to estimate and compare the historic range of nine scavenging birds from North America that went jointly extinct with their mammalian megafaunal prey in the Late Pleistocene. Although the severity and timing of their co-extinction are strongly correlated, there has been little analytical support in providing estimates for the possible geographic distribution of scavenging birds prior to the extinction event. To build an estimate of their historic range, I utilized rasters depicting the range of the mammal and bird species that co-occurred alongside the scavengers at different fossil sites. Using co-occurrence data to reconstruct the historic distributions of extinct scavenging birds was the selected approach because many extinct scavengers are known from very few fossil sites. Results showed that the estimated range size for extinct scavengers, based on avian co-occurrence data, was generally larger than the range estimates using mammal data. To measure the relationship between the distribution of scavengers and their prey, I compared the estimated ranges to the present-natural range of North American mammals using linear and spatial autoregressive models. The analysis revealed that both estimated ranges, using avian or mammalian co-occurrence data, were significantly positively correlated with and are significant predictors of present-natural mammalian diversity, but estimates based on mammals exhibited a stronger effect size and are thus a better predictor of present-natural mammalian diversity compared to using avian species. The results of this study determined a significant relationship between the extinct scavengers estimated distributions and present-natural mammalian diversity, providing biogeographic corroboration in support of the theorized co-extinction event in which the decline in mammalian prey was the causal link affecting scavenging bird declines. Future studies could employ similar methods and further test the procedure of using co-occurrence data from the fossil record to approximate the distribution of data-limited extinct species.