BREEDING BIOLOGY OF THE MONK PARAKEET

The Monk Parakeet (Myiopsitta monachus) is unique among parrots because it constructs stick nests rather than nesting in holes. This study provides a detailed description of the species' breeding biology and provides evidence that this species might breed cooperatively. Although many parakeet pairs were observed roosting in solitary nests, breeding occurred only in nests within colonies or chambers within compound nests housing other parakeets. The male was responsible for all or most of the nest construction and maintenance. He fed the female during the incubation and early nestling periods, but later in the nestling period both the male and female fed the nestlings. Most breeding attempts involved a male-female pair, but three separate breeding attempts were made by trios (two trios included a female and two males, and the third trio was composed of a male and two females). In the trios, one of the auxiliary bird contributed less to the breeding effort than the primary male and female. The observations of trios support the idea that Monk Parakeets are similar to coop- erative breeders, but the lack of cooperation in nest building indicates that colonial nesting may be a result of other benefits of group living, such as improved predator detection. Received 7 Jan. 1998, accepted I6 Aug. 1998. The social behavior of most parrots has re- mained unstudied, at least partly because of the difficulty of observing birds that are typ- ically far-ranging and often dwell in forest canopies. Compared to most of its relatives, the Monk Parakeet (Myiopsittu monachus) is a relatively tractable species for behavioral study. It is common throughout its range, gen- erally lives in semi-open habitat, and spends a large amount of time in the vicinity of its nests. Monk Parakeets are unusual among par- rots for building large domed nests instead of nesting in holes (Forshaw 1989). These nests are built of twigs and may include several chambers, each occupied by a different pair or group of birds. Nests are often clustered in the same or nearby trees to form colonies, and they are used for roosting as well as for breed- ing (Forshaw 1989). In Bolivia, Monk Para- keets (M. m. Zuchsi) build their stick nests on cliffs rather than in trees (Lanning 1991). The strong tendency to breed colonially, along with delayed breeding, reduced dispersal, and incidental helping led Bucher and coworkers (1991) to suggest that the Monk Parakeet breeding system shares some characteristics with cooperatively breeding species. The large stick nests built by these parrots are the center of much of their daily activity.