Managing the long‐term persistence of a rare cockatoo under climate change

Abstract

Summary1. Linked demographic-bioclimatic models are emerging tools for forecasting climate change impacts on well-studied species, but these methods have been used in few management applications, and species interactions have not been incorporated. We combined population and bioclimatic envelope models to estimate future risks to the viability of a cockatoo population posed by climate change, increased fire frequency, beak-and-feather disease and reduced management. 2. The South Australian glossy black-cockatoo Calyptorhynchus lathami halmaturinus is restricted to Kangaroo Island, Australia, where it numbers 350 birds and is managed intensively. The cockatoo may be at particular risk from climate change because of its insular geographic constraints and specialised diet on a single plant species, Allocasuarina verticillata. The cockatoo population model was parameterised with mark-resight-derived estimates of survival and fecundity from 13 years of demographic data. Species interactions were incorporated by using a climate-change-driven bioclimatic model of Allocasuarina verticillata as a dynamic driver of habitat suitability. A novel application of Latin Hypercube sampling was used to assess the model's sensitivity to input parameters. 3. Results suggest that unmitigated climate change is likely to be a substantial threat for the cockatoo: all high-CO 2 -concentration scenarios had expected minimum abundances of <160 birds. Extinction was virtually certain if management of nest-predating brush-tail possums Trichosurus vulpecula was stopped, or adult survival reduced by as little as 5%. In contrast, the population is predicted to increase under low-emissions scenarios. 4. Disease outbreak, increased fire frequency and reductions in revegetation and management of competitive little corellas Cacatua sanguinea, were all predicted to exacerbate decline, but these effects were buffered by the cockatoo population's high fecundity. 5. Spatial correlates of extinction risk, such as range area and total habitat suitability, were nonlinearly related to projected population size in the high-CO 2 -concentration scenario. 6. Synthesis and applications. Mechanistic demographic-bioclimatic simulations that incorporate species interactions can provide more detailed viability analyses than traditional bioclimatic models and be used to rank the cost-effectiveness of management interventions. Our results highlight the importance of managing possum predation and maintaining high adult cockatoo survival. In contrast, corella and revegetation management could be experimentally reduced to save resources.

Mechanistic models project bird invasions with accuracy

“…Feather lengths and depths were scaled according to the total mass of the modeled bird assuming isometric scaling 167 . Latin Hypercube sampling simultaneously varies the values of the input parameters to efficiently sample the parameter space 168 , 169 , and was used to first generate 1.000 model variants for each bird species considered here. Variable importance was then obtained by fitting a random forest 170 to model outcomes (using the True Skill Statistic TSS, an evaluation metric providing an equal weighting to commission and omission errors) 171 .…”

Simulated effects of roadkill and harvest on the viability of a recovering bobcat population

“…We used Poisson distributions to simulate demographic stochasticity in annual births (offspring born at year t + 1 to females at year t ) and binomial distributions to simulate stochastic variation in survival and sex ratio. We used a ceiling density‐dependence process to determine the abundance of each subpopulation (Harris et al 2012). Density dependence is related to life‐history strategy, and using a density‐dependence process alone can result in higher population viability and thus overestimation of population growth (Fowler 1981); therefore, we constrained the density‐dependent ceiling using estimated habitat suitability to ensure that abundance in each grid cell remained at realistic levels and related to resource availability.…”

Nature conservation on agricultural land: a case study of the endangered Carnaby’s Cockatoo Calyptorhynchus latirostris breeding at Koobabbie in the northern wheatbelt of Western Australia

“…They regarded this culling as successful because the Little Corella population increased in some areas, and no nestling Glossy Black-Cockatoo deaths were recorded. However, Harris et al (2012) conducted a population viability analysis of the Glossy Black-Cockatoo (GBC) population on Kangaroo Island, and noted that the "reduction in corella management indicates this culling was almost negligible because of the resilient GBC population." They ran their model on the basis of two Glossy Black-Cockatoos being lost each year to Little Corella, and recommended that culling could be stopped in some areas to conserve management resources.…”