Ever noticed the green parakeets flying around Rome and wondered what they were and how they came to be living in the city?

Rome actually has two distinct species: the rose-ringed parakeet (above), a tropical Afro-Asian bird with red beak that takes over the tree-hole homes of Rome's woodpeckers; and the monk parakeet (below), a less flashy and more discreet South American variety that builds communal wicker-like nests.

 Now a familiar sight in tree-lined neighbourhoods across the city, the birds do not migrate and are among the few parrot species to have successfully adapted to living in an urban environment.