Can fire-age mosaics really deal with conflicting needs of species? A study using population hotspots of multiple threatened birds
Verdon, Simon; Clarke, Michael (2022), Can fire-age mosaics really deal with conflicting needs of species? A study using population hotspots of multiple threatened birds, Dryad, Dataset, https://doi.org/10.5061/dryad.00000005s
Locations that support high densities of a species (“population hotspots”) have a disproportionate influence on species’ persistence. In fire-prone ecosystems, managers attempting to promote population hotspots of multiple species must understand how hotspot locations might shift with post-fire succession and how much overlap exists in the locations of population hotspots for multiple species. Mangers are then tasked with resolving fire-management conflicts in overlapping locations.
We studied three co-occurring threatened bird species in a fire-prone ‘mallee’ region of south-eastern Australia. We undertook field surveys for each species (1508 surveys; 540 sites; 9-ha each). We used N-mixture models to determine (a) what factors affect species’ density (including post-fire succession); (b) species’ population sizes; (c) locations of species’ current population hotspots and locations that may become population hotspots in the future as the post-fire successional state changes and (d) the degree of overlap in the current and possible future hotspots of species.
We found substantial variation in the densities of the three species across the study area, with roughly half of each species’ population occurring in only 20 percent of potential habitat (i.e. population hotspots). All species shared a preference for subtle depressions in the landscape, resulting in substantial overlap in their population hotspots. Two species had contrasting responses to post-fire succession in the subtle depressions. As a result, there was only a narrow post-fire period that supported population hotspots of both species, creating a challenge for fire managers in these shared locations.
Synthesis and Applications. Many studies make vague recommendations for fire-age mosaics that do not provide managers with the detail they need to implement appropriate fire-age mosaics. By contrast, we explicitly quantify, then balance the conflicting post-fire needs of species in locations that support population hotspots of multiple species. Using this approach, we develop principles to guide the implementation of fire-age mosaics in such locations. This approach represents a step towards applying fire-age mosaic theory to support effective species conservation.
This is bird survey data collected in the field. 9-ha area searches were undertaken during the austral spring of 2019. Repeat surveys were used to model detectability. Sites were surveyed 2 to 4 times and detection covariates recorded for each survey. Bird species abundances for the three study species were also recorded during each survey.
Becasue the number of repeat surveys varied between sites, there are missing values where no further surveys were conducted for that site. For example, sites that were surveyed only twice have missing values for columns relating to the third and fourth rounds of surveys.
Department of Environment, Land, Water and Planning, State Government of Victoria
Department of Environment and Water, State Government of South Australia
Holsworth Wildlife Research Endowment