Interannual and seasonal changes in the abundance of an urban population of the Burrowing Parrot (Cyanoliseus patagonus) in the Southwest of Buenos Aires Province

Abstract

The Burrowing Parrot (Cyanoliseus patagonus) is a threatened species whose populations have decreased as a result of habitat loss and degradation, capture for the pet trade, and historical persecution for considering it an agricultural pest. Recently, however, an apparent increase in its abundance has been reported in urban areas in the southwest of Buenos Aires province, Argentina, although this observation is not based on objective estimates. In this study we compare the abundance of Burrowing Parrots in Bahía Blanca (Buenos Aires) between 2014 and 2022. We monitored the individuals that use a communal roost in the main park of the city. This roost congregates almost all parrots within a radius of about 20 km. We established six counting stations defining a closed polygon around the park, and performed 52 seasonal counts at the time of arrival in 2014, 2018, 2019, 2020, 2021 and 2022. The number of individuals that congregated at the roost varied between 1767 and 21 104 over the years and seasons. The comparisons made do not reflect a significant increase in the number of parrots that arrived at the roost between the different springs, between the summers or between the autumn-winter seasons of the different years studied, except for the autumn-winter of 2019, which almost doubled the values corresponding to the same period of 2014. We also recorded a marked seasonal variation in parrot abundance that was repeated in all sampling seasons, with highs during autumn-winter.