Barbuda Warbler <i>Setophaga subita</i> and Yellow Warbler <i>S. petechia bartholemica</i> population assessment after Hurricane Irma

Summary Hurricane Irma devastated the island of Barbuda in September 2017. Motivated by the need to assess the population status of the endemic Barbuda Warbler Setophaga subita and resident Yellow Warbler S. petechia bartholemica , we used distance sampling to estimate total abundance (i.e. density and population size in a well-defined survey region, accounting for incomplete counts due to imperfect detection) in October 2017 and March 2019. Vocalising warblers were more detectable than non-vocalising warblers (two-tailed z scores &gt;2.01, P values &lt;0.04). In October 2017, detectability and density of the Barbuda Warbler were higher at points where the Yellow Warbler was undetected than detected ( z &gt; 2.20, P &lt;0.03), suggesting competitive interactions following the hurricane. However, detectability did not differ ( z = 0.45, P = 0.62) and density was higher ( z = 2.11, P = 0.03) for the Barbuda Warbler at points where the Yellow Warbler was detected than undetected in March 2019, suggesting non-competitive coexistence after population recovery. The density (i.e. no. individuals/ha) and population size (no. individuals in the 9,000-ha survey region) of the Barbuda Warbler increased ( z = -2.60, P = 0.01) from 0.27 (SE = 0.03) and 2,436 (SE = 261) in October 2017 to 0.40 (SE = 0.02) and 3,570 (SE = 171) in March 2019. The density and population size of the Yellow Warbler also increased ( z = -2.40, P = 0.02) from 0.68 (SE = 0.03) and 6,093 (SE = 269) in October 2017 to 0.80 (SE = 0.04) and 7,158 (SE = 358) in March 2019. Owing to the small distribution range and threats from hurricanes and habitat loss on the island, the Barbuda Warbler should remain classified as “Vulnerable” to extinction. However, the more abundant and widely distributed Yellow Warbler should remain classified as of “Least Concern”.