Myiopsitta monachus is a small, stocky parrot, measuring approximately 30 cm in total length (Campbell,1998) with a wingspan of 53cm and a mass of 90-120g (Spreyer and Bucher, 1998). M. monachus is mostly green with a gray or off white face, cheeks, throat and breast. They have a bright yellow lower abdomen and vent area. The flight feathers are blue-black, and the tail feathers are long and green. They have a pale orange or dull yellow bill and gray legs (Campbell, 1998) and a dark brown iris (Spreyer and Bucher, 1998). Immature M. monachus are a brighter green with a greenish forehead. (Campbell, 2000) They do not exhibit sexual dimorphism (Spreyer and Bucher, 1998), with males and females having identical plumage. Males are generally slightly larger than females, except during breeding season when the body mass of females increases slightly (Newman et al, 2004). They are usually found in loose flocks of 15-20 birds, although flocks of up to 100 are not uncommon. M. monachus are quite vocal with a wide vocabulary of screeches, squawks and chattering noises (Campbell 2000).

Myiopsitta monachus (monk parakeet) is a CITES-listed species. Please follow this link CITES- Myiopsitta monachus for more details. Roughly 5,000 species of animals and 28,000 species of plants are protected by CITES against over-exploitation through international trade.

Monk parakeets display several types of \"helping behaviours\" that may have contributed to their success as alien species. Included are communal nest building, delayed breeding, the presence of non-breeding mature adults, nest sentinel systems and reduced natal dispersal. After leaving the nest, young birds often remain close, building their own nests or adding on to an existing nest. Nests can be small, housing a single pair or up to one metre in diameter and weighing 200kg and house multiple pairs. Nests have roofs and entry holes, mainly on the underside and often multiple chambers for nesting pairs and small groups of non-breeding indivduals. (Spreyer and Bucher, 1998). \"Once the site of the nest structure is selected, individual monk parakeets construct a nest cavity, affixing it to the main nest structure.\" (Burger and Gochfeld, 2005). M. monachus are very social birds, having eleven or more different calls that each elicit a different response from others in the colony. (Campbell, 2000)

In the studied Punta Blanca population, Myiopsitta monachus (monk parakeet) eggs hatched asynchronously after 24 days. The hatch rate was just over 50%. The hatchlings are covered with yellow down and are fed by the parents via regurgitation (Spreyer and Bucher, 1998) for approximately 40 days, after which they leave the nest (Campbell, 2000). The nestlings reach a weight of approximately 106 grammes before fledging (Campbell, 2000).

Known for their beauty and intelligence, Myiopsitta monachus (monk parakeets) are a popular pet, especially in North America, since the 1960's (Campbell, 2000).

Myiopsitta monachus prefer open habitats. In their native range they populate savannah woodlands, farmland, plantations, orchards and cultivated forests (Campbell, 2000), from low elevations up to 1600m above sea level (Spreyer and Bucher, 1998). They are the only parrot that builds its own nest instead of using existing cavities. They weave sticks and spiny branches together to create a sturdy nest used year round for roosting. The nests are almost always 10 metres or more above the ground, often in tall trees (Spreyer and Bucher, 1998).

Studies of monk parakeet populations at Arroyito and Jesus Maria, Cordoba province, Argentina, showed that monk parakeets preferred Eucalyptus trees (Arroyito) and native trees (Jesus Naria) for breeding nests (Navarro, Martella, & Bucher, 1992). In its introduced range they live almost exclusively in urban areas, preferring open habitats, including parks, planted urban areas, golf courses, farms, gardens and orchards (Campbell, 2000).

In South America, gonadal development begins in August, peaks in November and declines rapidly thereafter. Testes enlarge to fifteen times their normal size and ovaries grow in similar proportion. This pattern supports the idea of a fixed annual cycle driven by a photoperiod. South American monk parakeets copulate in October while North American birds copulate in the spring months as the photoperiod increases. In a study of a Myiopsitta monachus population in Punta Blanca in the Buenos Aires province of Argentina, pairs produced the first eggs in mid-October. The average clutch size was 7 eggs (range 5-12) (Campbell 2000).

In their native range, M. monachus are generalist granivores and will eat maize, millet, sorghum, sunflowers and other seeds, as well as some fruits, nuts, berries and insects. Year round favorite foods include thistle (Asteraceae) and grass (Poaceae), and fruits of palm and other native trees, largely tala (Celtis spinosa). (Spreyer and Bucher, 1998). Monk parakeets are highly flexible in their food habits (Pruett-Jones et al, 2007). In their introduced range, they feed on the seeds and fruits of exotic ornamental plants and on bird seed provided year round by humans. (Hyman and Pruett-Jones, 1995). They use their large beak to consume seeds and take bites from large pieces of fruit. They have also been seen cracking pine cones to get to the seeds and snipping the heads off dandelions and eating the seeds. In winter, M. monachus often feeds in large flocks of several hundred while a few sentinels sit on high perches and search for predators. During the breeding season, flocks larger than 4 birds are rare. M. monachus generally feeds 3.2-8km from the nest site and may forage as far as 24km away durning the non-breeding season. (Spreyer and Bucher, 1998).

Nearly 65,000 monk parakeets were imported into the U.S. from 1968 to 1972 (Spreyer and Bucher, 1998).

In its native range, M. monachus is considered a significant agricultural pest, often causing damage to field crops and orchards. There have also been reports of transmission lines short-circuited by nesting birds. In its introduced range, impacts are mainly associated with nesting behaviours. Monk parakeets build large bulky nests on communication towers and electric utiliites such as distribution poles and transmission towers. On communication towers they are simply a maintenance problem and do not affect communications. However nests on electric utilities can cause outages and fires, as the large nests can complete electric circuits. This problem is pronounced in wet weather. Monk parakeet nests can cause significant effects to electric utilities including decrease in electric reliability, equipment damage, and lost revenue from nest and bird caused power outages, increase in operation and maintenance costs associated with nest removal and repair of damaged structures as well as public safety concerns (Newman et al, 2004).Costs associated with monk parakeets can be quite considerable. For example, during a five-month period in 2001 in South Florida 198 outages related to monk parakeets were logged. Lost revenue from electric power sales was $24,000 and the cost for repair of outages was estimated at $221,000 (Newman et al, 2004). However in it's introduced range M. monachus has not caused the agricultural devastation predicted, nor has there been any solid evidence that native fauna are negatively affected by their establishment. There is also the possibility that monk parakeets will spread plant diseases by transporting infected planting material to uninfected trees. For example, in Florida citrus canker is a major concern (Newman et al, 2004). There has also been some speculation that growing urban populations of M. monachus could become source populations for surrounding areas. The birds are widely admired by city dwellers who see little other wildlife (Campbell, 2000). Fitzwater (1988) also states \"In addition to being a fruit crop pest in South America, it has great potential for dissemination of Newcastle disease. It also cuts trigs and buds from ornamental trees. They are one of the most raucous of birds.\"

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