Kathleen Etherington of Dunedin, asks :-
Have the native birds of NZ influenced non-native birds to alter and improve their songs?
Laura Molles, a behavioural ecologist at Lincoln University, responded.
Most songbirds have a relatively brief "sensitive phase" early in their life during which they hear and memorize songs from adults of the same species. Although it is possible that young non-native birds might copy the songs of native birds, it's unlikely to be common for a few reasons. One reason is that many of our non-native songbirds don't live in habitats where native species are abundant, so don't have the opportunity to hear native birds' songs. Secondly, many species have an innate mental "template" that limits what kinds of songs they will learn. Finally, for most species, learning native birds' songs would be disadvantageous; if potential mates or rivals can’t recognize them, they're not going to be very successful.
There are, however, some noticeable exceptions. Some songbirds are positively obsessed with vocal variety. (In many species, females find large repertoires very appealing). Perhaps the most familiar non-native examples are song thrushes and starlings. Starlings may imitate several native songbirds in rapid succession: grey warbler, fantail, bellbird, and even less musical natives like gulls. Song thrushes also regularly insert elements from other species into their songs. However, they'll also imitate car alarms, which doesn’t say much for their taste. And, of course, the street runs both ways; some of our native birds can learn from non-natives. Tui are particularly good mimics, and can even do very good imitations of human voices.
So, in some cases songs have changed, but the same would be true, to some extent, even in different areas of a species' native range. Whether the changes that have occurred in New Zealand are an improvement, of course, is a matter of opinion. When it comes to birdsong, as with music, beauty is in the ear of the beholder!