Details of the taxa included in this study.

PSMC = Pairwise Sequential Markovian Coalescent, ENM= Ecological Niche Modelling, y = yes, n = no.

Pairwise Sequential Markovian Coalescent (PSMC) plots using the settings –p “2 + 2 + 30 * 2 + 4 + 6 + 10” displaying reconstructed effective population size values with time for passerines (above) and non-passerines (below) based on whether habitat availability increased (left) or decreased (right) during the Last Glacial Period (LGP).

Colours indicate the archipelago/island the bird belongs to, and the line style indicates the dietary habit of the bird species. Bold lines indicate large (> 50 g body mass) bird species. The grey bands indicate the approximate durations of the last interglacial (LIG) and the last glacial maxima (LGM). Black arrows indicate if the habitat availability increased or decreased during the LGP. A mutation rate of 1.4 x 10e–9 years/site and a generation time of 2 years for passerines, and a mutation rate of 1.91 x 10e–9 years/site and a generation time of 1 year for non-passerines were used to generate plots. Zosterops hypoxanthus is not displayed because its Ne values far exceed those of the other species.

Example of Ecological Niche Modelling plots for species from Papua (Cnemophilus loriae), Australia (Alectura lathami), the Philippines (Irena cyanogastra), and the Caribbean (Puerto Rico, Todus mexicanus).

LIG = Last Interglacial. LGM = Last Glacial Maximum. MDH = Mid Holocene. CUR = Current. The continuous heatmap represents the probability of occurrence of the species and red points are known occurrences from GBIF. For all the plots see figure S2.

Results of the best Bayesian multivariate regression model performed.

The response variable represents the changes in effective population size (increased (=1) or decreased (=0)) during the last glacial period. Circles represent mean values and lines represent 95% confidence intervals. Model parameters and coefficients are provided in table S6. ΔHabitat = the change in suitable habitat from the Last Interglacial to the Last Glacial Maximum.