Physical attractiveness, constraints to the trade and handling requirements drive the variation in species availability in the Australian cagebird trade

- 55.2% of all bird species present in the Australian cagebird trade are alien species.
- Price and abundance are inversely correlated for Australian finch species in the domestic trade.
- Smaller and drabber birds tend to be less expensive than larger more colourful birds.
- Native Australian birds, and species easier to trade and keep, tend to be cheaper.

Understanding the traits that drive the demand for exotic pets is crucial for improving our ability to prevent the introduction of new invasive species. We investigated the factors influencing species availability within the Australian cagebird trade. We predicted that species price should be an informative indicator of the species abundance in the trade, and that physical attributes, origin of the species, and limitations for free trade and for captive breeding should be important drivers for species price. We investigated the quantitative relationship between species price and these factors using phylogenetically informed models.357 species were present in the Australian cagebird trade, and 55.2% were alien. We found a strong negative relationship between species price and abundance. We identified that smaller-bodied, drabber species were cheaper than larger, more colourful species, and that native birds, species that were mostly exempt from regulations to their keeping and trading, and species easier to keep in captivity, tended to be cheaper. Assuming that the more widely held a species the greater the likelihood that is to be released, we propose that price can be used as a proxy for abundance when screening the species that have a higher risk of being deliberately or accidentally introduced.