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Expert knowledge is widely used for assessing the conservation status of little-known species. Pterocymbium oceanicum is a large, emergent tree endemic to Fiji. Experts classified the species as 'Critically Endangered' (IUCN Red List) in 2016 and estimated the population size at <250 mature individuals with the largest subpopulation consisting of a single stand of 100 individuals. We surveyed this stand and counted 133 individuals, which validated the expert estimate. However, we discovered an additional three stands nearby, increasing the total subpopulation size to 433 individuals. Therefore, the expert estimate reliably and conservatively estimated population size but missed important information. Field surveys suggest that P. oceanicum has a narrow ecological niche as a long-lived early pioneer at mid-elevations (400–800 m) in seasonally dry forests, one of Fiji's most degraded ecosystems. The introduced African Tulip Tree, Spathodea campanulata , is invading the sampled subpopulation and shares the characteristics of being a large, fast-growing and early successional tree. Therefore, the narrow niche of P. oceanicum may now be threatened by S. campanulata. Our study highlights that expert knowledge can provide valuable information about threatened species but also has limitations. IUCN Red List assessments based solely on expert assessments should therefore be cautiously interpreted. The invasion by S. campanulata poses a serious threat to P. oceanicum and needs to be carefully monitored, with the impacts of S. campanulata on the establishment and growth of P. oceanicum requiring urgent investigation. Pterocymbium oceanicum is a large, emergent tree endemic to Fiji that was classified as 'Critically Endangered' (IUCN Red List) based on expert knowledge. Our field survey quadruples the known size of the largest subpopulation by discovering three previously unknown stands, highlighting the value and limitations of expert knowledge for conservation assessments. Furthermore, we found that the species has a narrow ecological niche and is potentially threatened by the invading African Tulip Tree, Spathodea campanulata , which should be carefully monitored. [ABSTRACT FROM AUTHOR]

Half of Fiji's 66 land bird species are endemic and 15 species are threatened with extinction following ~70% deforestation. Under conditions of large-scale habitat loss, secondary vegetation can be important for woodland biodiversity conservation. This study compares avian abundance and diversity in secondary vegetation on Viti Levu, Fiji. We use avian point surveys at replicate sites in regenerating mahogany plantation (Colo-i-Suva; eastern lowlands), regenerating native forest (Koroyanitu National Heritage Park; western highlands) and grassland (Koroyanitu National Heritage Park). We ask if there are differences in avian abundance and species richness across habitat types. In total, we recorded 1063 birds from 33 bird species. Regenerating forest sites had the greatest species richness with mostly endemic and native woodland bird species and few introduced species. Regenerating plantation sites harboured a comparable number of endemic species and threatened species as regenerating forest sites but had significantly fewer native species and no introduced species. We recorded the most birds at grassland sites as well as the most introduced species. The findings of this study underscore the importance of regenerating native forest and regenerating plantation as habitats for Fiji's endemic woodland birds. Increasing the expanse of regenerating forest sites should be considered for conservation planning to sustain Fiji's extant birds. [ABSTRACT FROM AUTHOR]