Monk Parakeet nidification in an urban area of Argentina (2008-2017)

Monk parakeet is a successful invasive species in many cities around the globe. In the Pampean region of Argentina, the changes in the land use promoted their expansion of Monk parakeets. At La Plata city, Monk Parakeets were recorded since 2000, and since then we monitor their population. The objective of this work is to report the current status of the population and to explain the progressive growth and expansion. During the last decade, we surveyed urban parks of La Plata city looking for trees and artificial structures where parakeets build nests. We counted 689 nests and 1452 chambers (2.26 chambers/nest). Nests were found in 330 different pillars, from which 96% were trees (87% Eucalyptus sp., 8.5% Araucaria angustifolia, 0.6% other tree species) and 4% of nests were in light pillars. We found 2.29 nests/pillar. Nests contained one (38%), two (31%), three (15%), four (9%), five (5%), six (2%) and seven or more (1.6%) chambers. Between 2008 and 2017 the number of nests and trees with nests duplicates; while the number of chambers increased four times. The relative percentage of nests with a single chamber decreased along the studied period. In the other hand, the number of nests with two, three or more chambers increased. Our observations support the hypothesis of, after occupying a new site, Monk Parakeets tend to increase the number of chambers per nests, instead build new ones.