Listen to part of a lecture in an animal behavior class.(female professor) Okay, we\'ve been talking about bird communication, uh, their songs and calls. Can anyone remind us of the differences between the two?(male student) Well, bird songs are usually produced only by males and they\'re used to attract mates or to stake out territory.But both males and females produce calls, which are used for things like warnings or begging for food.(female professor) Right, and is there anything else?(female student) Yeah. Male birds learn their songs when they\'re young, but calls are usually instinctive. They\'re genetically programmed, not learned.(female professor) Good. Now some birds that don\'t even produce songs are great imitators. Right?Think about members of the psittacines family commonly referred to as parrots.Psittacines comprise nearly 400 species, including true parrots, parakeets, macaws, cockatoos and so on.In captivity, they mimic human speech, but we don\'t really understand why, what purpose would this trait, this ability to mimic sound so accurately serve them in the wild.To answer that we must look at how parrots communicate in the wild.Like I said unlike other bird species, parrots don\'t produce songs, they produce only calls.And studies suggest that unlike most other birds, the parrots’ calls aren\'t genetically programmed, but learned and that they continue to learn new calls throughout their lives.Let\'s look at a recent study about parrot communication.(male student) I read it\'s difficult to study parrots because they roost high up in the trees. And the males and females look really similar.(female professor) Yes. And many species have beaks, strong enough to tear off those bands——researchers put on birds\' legs to identify them.But there have been a few studies of parrot communication, including the one we\'ll discuss today.But first, some background, in the 1980s, a researcher who was studying birds on a cattle ranch in Venezuela noticed several small psittacines called parrotlets who were nesting inside hollow spaces in the fence posts.He wondered if he could make artificial nesting boxes that would appeal to these parrotlets. So, he designed some and eventually ended up with over 100 nests.Researchers have been studying the parrotlets there ever since. This research has yielded a wealth of data about parrot behavior and life histories.(female student) So, the nesting boxes made this type of parrots easier to study?(female professor) Right. Also, unlike most psittacines, males and females are easily distinguishable, plus they tolerate being handled by researchers. These parrotlets even leave their leg bands alone.The studies followed more than 8,000 parrotlets throughout their lives, keeping track of all sorts of things, such as who\'s related to whom.So, when ornithologist Carl Berg wanted to study communication between parrot parents and their nestlings in the wild, he had the perfect place to do it.(male student) Okay, so here communication means calls, and most birds make a lot of different calls, right? What kind did Berg want to study?(female professor) He was interested in what we call a contact call, the most basic call. To us, a contact call sounds like a few simple peeps.But researchers have proposed that these calls are like the parrots’ names.And what Berg wanted to do was find out if these contact calls were learned behaviors or instinctual.What he did was this: first, he swapped eggs among 9 nests so that some sets of chicks were raised by unrelated parrots like foster parents. He left 8 other nests untouched as controls.Then he made weekly video and audio recordings inside the nests after the chicks hatched. And he made recordings outside the nest when the parents came and went.Now the sounds are too fast for us to be able to hear the differences.So, Berg converted them into spectrograms or pictures of the sounds. Then he analyzed the spectrograms using computer programs that search for similarities.Interestingly, he found that the parents provide a basic call template to the chick at about 3 to 4 weeks, which each chick learns and slightly modifies to make its own contact call, its own name.He also found that calls of nestlings are more similar to the calls of their primary caregivers, the foster parents than to any other adults, even their biological parents.And this similarity helps parents recognize their nestlings after they\'ve left the nest.(male student) Why do they need to recognize each other?(female professor) Because parrotlets parents continue to feed their fledglings for about 3 weeks after they\'ve left the nest.Since fledglings roost in large groups, parents have to be able to find them. And Berg believes that they do so using those calls.(female student) So, but what exactly does this have to do with why parents in captivity mimic human voices?(female professor) Ah. See, Berg discovered that the nestlings not only create and learn their own names, they learn each other\'s names as well.Just as the parents have to learn each individual fledgling’s name in order to find them after they\\\\\\\'ve left the nest.So, we have the first verified explanation for why mimicry is so important to psittacines in the wild.