Territorial dynamics of the Smooth-billed Ani Crotophaga ani (Cuculidae) in the agricultural zone of Santa Cruz Island, Galápagos

Abstract

The Galápagos Islands are unique for their biodiversity and endemism. Unfortunately, due to human presence, they have undergone various alterations to their ecosystems, including the introduction of invasive species. By 2016, 1,579 introduced species were recorded, of which 1,476 have established themselves as residents. Among these is the Piquiliso Cuckoo Crotophaga ani. This Cuculidae was brought to Galápagos in the early 1960s as a potential biological control method against a tick plague in cattle, as it was mistakenly believed that its diet was based on these invertebrates. Since then, C. ani has spread throughout the archipelago, with records on all the main islands except for Darwin. Little is known about its ecology in Galápagos, which hampers the ability to quantify its negative impact on the ecosystem. This research reveals for the first time how C. ani occupies its territories in the agricultural zone of Santa Cruz. This species exhibits social habits, roosting in unique collective roosts for each group at night. In the study area, a total of 37 roosts were monitored, and the birds entering these roosts were counted to determine the composition of each territory. On average, each group consisted of nine individuals (five adults, two juveniles, and two of uncertain age). Additionally, GPS transmitters were placed on 11 individuals from different groups to monitor their movements. These results revealed that the average size of their territories is 7.99 ha, primarily located in areas with low vegetation such as grasslands or crops. This data represents a significant advance in the understanding of this invasive species, paving the way for the development of a control plan to mitigate its negative effects on Galápagos biodiversity.