Learning in early life is apparently important to all parrots, and much of that learning is social learning. Social interactions are often practised with siblings, and in several species, creches are formed with several broods, and these, too, are important for learning social skills. Foraging behaviour is generally learnt from parents, and can be a very protracted affair. Suprageneralists and specialists are generally independent of their parents much quicker than partly specialised species which may have to learn skills over long periods of time as various resources become seasonally available. Play forms a large part of learning in parrots; it can be solitary, and related to motor skills, or social. Species may engage in play fights or wild flights to practice predator evasion. An absence of stimuli can delay the development of young birds, as demonstrated by a group of vasa parrots kept in tiny cages with domesticated chickens from the age of 3 months; at 9 months, these birds still behaved in the same way as 3-month-olds, but had adopted some chicken behaviour.[34] In a similar fashion, captive birds in zoo collections or pets can, if deprived of stimuli, develop stereotyped behaviours and harmful behaviours like self plucking. Aviculturists working with parrots have identified the need for environmental enrichment to keep parrots stimulated.