ReadMe for P.R. Martin, C. Freshwater, and C.K. Ghalambor, ms. The outcome of most aggressive interactions among closely related bird species are asymmetric. This readme file describes the variables in the two data files (dataset_locations_lumped.csv and dataset_locations_separate.csv) that were the basis of the above manuscript. Variables in the two datasets are identical, except that a “location” column is included in dataset_locations_separate.csv, and columns related to body mass are included in dataset_locations_lumped.csv. For any further queries please contact: pm45@queensu.ca number = comparison number group = one of four groups used in the analysis [interactions involving: vultures (Cathartidae and Accipitridae), hummingbirds (Trochilidae), woodcreepers and antbirds (Dendrocolaptidae and Thamnophilidae), and North American congeners (NAm.birds, representing diverse families; see Freshwater et al. 2014 for details)] order = taxonomic order of species A and B (following Gill and Donsker 2010) family = taxonomic family of species A and B (following Gill and Donsker 2010) genus.A = taxonomic genus of species A (following Gill and Donsker 2010) species.A = species name for species A (following Gill and Donsker 2010) genus.B = taxonomic genus of species B (following Gill and Donsker 2010) species.B = species name for species B (following Gill and Donsker 2010) win.A = number of aggressive interactions between species A and B that were won by species A win.B = number of aggressive interactions between species A and B that were won by species B sum.win = total number of aggressive interactions observed between species A and B (i.e., win.A + win.B) binom.test = P value from a binomial test on the proportion of wins by species A out of the total number of aggressive interactions between species A and B (i.e., sum.win); binomial tests were run in the program R (binom.test; R Core Team 2014) prop.won = the proportion of aggressive contests between species A and B that were won by species A (i.e., win.A/sum.win) location = the geographic location where the data were collected (in the dataset_locations_separate.csv file only) interaction.data.reference = the reference(s) for data on aggressive interactions mass.A = average mass (in grams) of species A (in the dataset_locations_lumped.csv file only); NA refers to species where mass data were not available mass.B = average mass (in grams) of species B (in the dataset_locations_lumped.csv file only); NA refers to species where mass data were not available larger.dom? = whether (value of 1) or not (value of 0) the heavier species won more than half of the aggressive interactions; NA refers to cases where mass data for species A or B were not available %.diff.mass = [the mass of the subordinate species (i.e., the species that won the minority of aggressive interactions) subtracted from the mass of the dominant species (the species that won the majority of aggressive interactions)], divided by the mass of the subordinate species, multiplied by 100 (to present as a percentage) (in the dataset_locations_lumped.csv file only); NA refers to cases where mass data for species A or B were not available, or where species A and B won the same proportion of aggressive interactions mass.reference = the reference(s) for data on mass (in the dataset_locations_lumped.csv file only) References Freshwater, C., C.K. Ghalambor and P.R. Martin. 2014. Repeated patterns of trait divergence between closely related dominant and subordinate bird species. Ecology 95:2334-2345. Gill, F., and D. Donsker, eds. 2010. IOC World Bird Names (v 2.6). Available online at http://www.worldbirdnames.org. R Core Team. 2014. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL http://www.R-project.org/.