Roost Culling as an Effective Management Strategy for Reducing Invasive Rose-Ringed Parakeet (Psittacula Krameri) Populations

Abstract

Rose-ringed parakeets (Psittacula krameri) are one of the most widespread invasive avian species worldwide. This species was introduced to the island of Kaua‘i, Hawai‘i, USA, in the 1960s. Depredation of crops by this species causes extensive economic losses. Large congregations in evening roosts damage trees and lead to excessive noise and droppings in public areas. We evaluated the efficacy of a roost culling program conducted by an independent contractor from March 2020 – March 2021. We estimated island-wide minimum abundance was 10,512 parakeets in January 2020 and 7,372 in April 2021. Over 30 nights of culling, approximately 6,030 parakeets were removed via air rifles with 4,415 (73%) confirmed via carcasses retrieval. An estimated average of 45 parakeets were removed per hour of shooter effort. The ratio of culled juveniles to adults was approximately 1.6:1.0. Age and sex structure of animals removed varied seasonally; the proportion of adult females removed in 2020 was 1.9× greater when culled outside of the estimated nesting season. Of the four roosts where culling occurred, the parakeets fully abandoned three and partially abandoned one site; of the three fully abandoned roosts, an estimated average of 29.6% of birds were culled prior to roost abandonment. This study was conducted during the COVID-19 pandemic, when tourist numbers and foot traffic were greatly reduced; it is unknown how public perception of roost culling in public areas may impact future efforts. Findings can be used to inform implementation of roost culling for management of nonnative rose-ringed parakeet populations.