Fig 1.
Naturalized and studied number of species in each region.
Number of naturalized species (black bars) and of studied species (grey bars) in the nine regions considered. Numbers between parentheses indicate the number of articles analyzed.
Fig 2.
Relation between mean impact value and the number of studies conducted for every impact category.
Number of studies conducted for every impact category (x axis) and the corresponding impact mean (y axis). Bars represent the standard error. Vertical and horizontal lines are located at the mean of x and y axes respectively and separate points in four quadrants according to the relative number of studies and the level of impact. Categories “chemical, physical or structural impact on the ecosystem”, “grazing/herbivory/browsing”, and “interaction with other non-native species”, are abbreviated to “physical impacts”, “grazing”, and “interactions”, respectively.
Fig 3.
Impacts of avian families on natural ecosystems.
Bars represent global impacts of the family and black points the average impact of the family. Only families with reported impacts are shown. Categories “chemical, physical or structural impact on the ecosystem”, “grazing/herbivory/browsing”, and “interaction with other non-native species”, are abbreviated to “physical impacts”, “grazing”, and “interactions”, respectively.
Table 1.
Negative and positive impacts of the few bird species with reported benefits in the bibliography.
Fig 4.
Relation between known impact of a species and its residence time.
Each point represents the event of introduction of one species to one region of the world. Multiple R-squared: 3.30e-05, Adjusted R-squared: -0.02, p = 0.97.
Fig 5.
Relation between mean impact score by category and mean residence time.
Points represent the mean values and error bars the standard error. This graph shows only the four categories that have at least seven data points.