2.1 Sample collection
To obtain indicative genetic diversity metrics across mainland Tasmania, we sampled between five and eleven scrubtits from seven a-priorisubpopulations on mainland Tasmania (including Bruny Island) during the non-breeding season (January – March 2021). Due to small population sizes and licensing restrictions on King Island, we sampled five individuals from three locations during the same non-breeding season (Table 1, Figure 1). We trapped scrubtits using a single 6m mist net and one minute of scrubtit song broadcast using portable speakers (ANU animal ethics permit # A2021/33). We sampled blood (< 20 μl per individual) using the standard brachial venepuncture technique with a 0.7mm needle into 70% ethanol. For two individuals from whom we were unable to safely obtain blood, we collected feathers shed during handling. One male individual was collected under licence (see acknowledgements) for genome sequencing, from which organ tissue samples (heart, spleen, kidney, gonads, brain, liver) were taken (Table S1). For each individual we took standard morphometric measurements and scanned for any unusual physical features such as feather abnormalities or skin lesions that may be indicators of poor health. A single observer (CY) sampled and measured all birds, and the maximum capture time was 35 minutes. No birds showed adverse reactions to sampling and all flew off strongly upon release. The fifteen individuals sampled on King Island was the maximum permissible sample size under licence conditions.