Parrot Breeding Although there are a few exceptions, parrots are monogamous breeders which nest in cavities and hold no territories other than their nesting sites. Only the Monk Parakeet and five species of Agapornis lovebird build nests in trees, and three Australian and New Zealand ground parrots nest on the ground. All other parrots and cockatoos nest in cavities, either tree hollows or cavities dug into cliffs, banks, termite nests or the ground. The eggs of parrots are white. In most species the female undertakes all the incubation, although incubation is shared for a few species. The female remains in the nest for almost all of the incubation period and is fed by the male. The chicks are altricial, usually hatched naked (although some have down). The female remains with the chicks for 1 to 2 weeks, again fed by the male, until the chicks are larger and have gained some feathering, and no longer require constant brooding. The chicks tend to huddle together to keep warm. As typical of K-selected species, the macaws and other larger parrot species have low reproductive rates. They require several years to reach maturity, produce one or very few young per year, and sometimes do not breed every year at all. Intelligence Studies with captive birds have given us insight into which birds are the most intelligent. While parrots have the distinction of being able to mimic human speech, studies with the African Grey Parrot Talk have shown that some are able to associate words with their meanings and form simple sentences (see Alex and N'kisi). Along with crows, ravens, and jays (family Corvidae), parrots are considered the most intelligent of birds. The brain-to body size ratio of psittacines and corvines is actually comparable to that of higher primates. One argument against the supposed intelligent capabilities of bird species is that birds have a relatively small cerebral cortex, which is the part of the brain considered to be the main area of intelligence in other animals. However, it seems that birds use a different part of their brain, the medio-rostral neostriatum/hyperstriatum ventrale, as the seat of their intelligence. Not surprisingly, research has shown that these species tend to have the largest hyperstriata, and Dr. Harvey J. Karten, a neuroscientist at UCSD who has studied the physiology of birds, discovered that the lower part of avian brains are functionally similar to ours. Not only have parrots demonstrated intelligence through scientific testing of their language using ability, but some species of parrot such as the Kea are also highly skilled at using tools and solving puzzles.