Time-window of occurrence and vegetation cover preferences of Dartford and Sardinian Warblers after fire

Abstract

Wildfires are the most extensive and severe disturbance affecting the shrublands where Sardinian and Dartford Warblers (Sylvia melanocephala and S. undata) abound. Estimating the long-term use of burned habitats by these species (i.e. their time-window of occurrence) is fundamental to understanding their regional distribution and to plan possible conservation measures for the near-threatened Dartford Warbler. In this study, we describe the post-fire time-window of occurrence and cover preferences of the two warblers using an abundance dataset, gathered by point counts over 22 consecutive years, and a density dataset, resulting from territory mapping of four different plots for up to 8 years. Both datasets span before and after fire. The two species colonized burned areas as soon as the second year after fire. The Dartford Warbler showed its highest abundance between 4 and 9 years after fire and disappeared after 16 years or more. The Sardinian Warbler had a peak of abundance at 9 years, but the study was not long enough to record its local extinction. Partial least squares regression showed that abundance at points and plot density of the Dartford Warbler were positively related to the plant cover between 0.25 and 1 m, whereas vegetation between 0.5 and 4 m was important for the Sardinian Warbler. The Dartford Warbler, therefore, depends on the existence of dense and low shrublands, that are often the result of past fires.