Genetic analyses confirm multiple introductions of Red-whiskered Bulbuls in South Australia

Keeping alien birds in Australia poses a significant environmental and agricultural biosecurity risk if birds escape or are released from captivity. Red whiskered Bulbuls were introduced to Australia in 1865 and have subsequently become established in the wild in New South Wales and Victoria, but are not established in South Australia, where they are a declared pest bird. Between 1993 and 2018, 19 birds were found and removed from the wild or captivity in the Adelaide Hills and Adelaide suburbs, South Australia. We used mitochondrial DNA sequences and nuclear single-nucleotide polymorphisms (SNPs) to examine the geographical origin of these red-whiskered bulbuls in South Australia, the minimum number of birds that were introduced, and the relationship within and between the captive and wild birds. We found two mitochondrial DNA haplotypes, suggesting a minimum of two females were introduced into South Australia. Nuclear SNPs revealed two main clusters of individuals: (1) all 7 wild Adelaide Hills birds, and (2) all 11 captive birds plus one wild Adelaide suburbs bird, suggesting two separate origins. Wild birds were first- or second-degree relatives, indicating that this was a breeding population, but they were not derived from the captive Adelaide population. None of the captive birds were closely related, suggesting that captive birds were not yet a breeding colony and had been sourced from unrelated individuals, probably in eastern Australia. Our results show that molecular methods are a valuable tool in the biosecurity innovation suite for understanding the provenance of escaped biosecurity risk species.