such limits are required unless a detailed knowledge of the inter-specific and intra-specific variation exists for each mtDNA gene. Secondly, the number of reference sequences available for each gene (12S and Cytb) was considered, together with a determination as to whether reference sequence(s) had arisen from published work (as opposed to direct submissions to GenBank which has circumvented peer review). Thirdly, the number of available reference sequences for other closely related species was also an important consideration, because if a group (e.g. cockatoos) had been genetically well characterised, the chance of misidentifying a sample as a closely related species decreased.