History, status, and productivity of the Red-crowned Amazon Amazona viridigenalis in the Lower Rio Grande Valley of Texas

Abstract

SummaryNewly established populations of endangered species can help mitigate declines elsewhere and can be a valuable genetic reservoir. When these populations are located within anthropogenic habitats, they may also help mitigate the potential biodiversity loss created by urbanization. The Red-crowned Amazon Amazona viridigenalis is an endangered species that has become naturalized in multiple urban areas throughout the United States and Mexico, and these populations may currently outnumber the population within their historical habitat. While these urban populations may hold the majority of this endangered species, very few studies have analyzed the status and trends of this species, or of threatened parrots in general, in urban areas. Our study focuses on an urban Red-crowned Amazon population in the Lower Rio Grande Valley (LRGV) of Texas: the only parrot population currently recognized as native to the United States. To determine a timeline of Red-crowned Amazon arrival and growth in the LRGV, we reviewed published literature and online citizen science databases. To quantify current population levels and trends, we conducted 412 surveys at all known roost sites throughout the LRGV from January 2016 through April 2019. We also quantified the ratio of adult and juvenile parrots at roosts. Our data suggest the species has been present in the LRGV consistently since the 1970s and showed rapid growth from the mid-1990s through roughly 2016. Roost counts suggest there is currently a minimum LRGV population of about 680 and the population has been relatively stable over the last 3.5 years. Productivity averaged 19% over three breeding seasons, suggesting successful internal reproduction. This study provides important baseline information for the management and conservation of Red-crowned Amazons in the region and provides a valuable timeline on the beginnings and trends of this recently established urban population of Amazona parrot.