Document ID: chunk:federal_register_of_legislation:F2024L01094:body:0:p20
Version: federal_register_of_legislation:F2024L01094
Segment Type: other
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Character Range: 59569–62720

At present, this novel technique is a highly effective and inexpensive method of reducing parasitism of chicks. However, further research is required to manage this threat in the longer term.

3.2.6 Small population size
Small, isolated populations may lose their long-term genetic viability (Barrett et al. 1994; Frankham et al. 2019). Population bottlenecks—where a population's size is reduced for at least one generation—can significantly reduce genetic diversity through genetic drift (random changes in the gene frequencies of a population from generation to generation). A small population size can also lead to inbreeding depression, where the biological fitness (survival and fecundity) of the population is reduced due to mating between related individuals, and increased expression of deleterious genes.

Recent genetic analysis of forty-spotted pardalotes completed by Alves et al. (2023) showed previously undetected population genetic structure corresponding to geographical barriers and fragmentation. North Bruny Island has the highest allelic richness, followed by Tinderbox Peninsula, South Bruny Island and Maria Island (Alves et al. 2023). In terms of contribution to total allelic richness across the species, North Bruny Island and Maria Island populations contributed the most genetic diversity (Alves et al. 2023). Thus, conserving these two populations is of high conservation value. The genetic variability of the Flinders Island subpopulation is still unknown. Inbreeding, in addition to habitat loss from fire, may have contributed the rarity of forty-spotted pardalotes on Flinders Island (Bryant & Webb 2014).

Alves et al. (2023) concluded that genetic management of forty-spotted pardalotes at this present time is not needed, though some small local populations are vulnerable to genetic stochasticity. Instead, habitat restoration should be prioritised to increase population size, especially on Bruny Island and the adjacent Tasmanian mainland. This research can be used to inform any future translocation trials, including defining management units and sourcing founder stock (Alves et al. 2023). Genetic monitoring should also be implemented as this information will be crucial to identify whether genetic management will be required in the future.

Small population size may also make forty-spotted pardalotes more vulnerable to competition from striated pardalotes and other species. Small breeding populations of forty-spotted pardalotes are more vulnerable to invasion by nesting striated pardalotes (see 3.2.7 Competition for nest hollows) when compared to the core areas of large forty-spotted pardalote populations (Woinarski & Rounsevall 1983; T Cochran & A Hingston 2022. pers comm 10 January). This pattern likely reflects habitat conditions as in their optimal habitat, specialists are usually the dominant species, but in degraded habitats they can become the subordinate one (Futuyma & Moreno 1988; Kassen 2002).

3.2.7 Competition for nest hollows
Striated pardalotes and tree martins compete with forty-spotted pardalotes for nest cavities with small entrances and deep chambers, often evicting them