Bird song (12) – Great Tits (5)

In 1984, from pretty close to this time of year, and for a two-week period, I helped a fellow post-doc at the Zoology Department in Oxford carry out a field experiment in the University Parks on song recognition in Great Tits.

We studied 13 male Great Tits holding territories for at least the second year (Great Tits don’t live long) and which had both a new territorial neighbour this year and a neighbour from a previous year too. And we did playback experiments, playing the neighbours’ songs from the right place (ie the territorial boundary where that neighbour’s territory actually was) and the wrong place (the other side of the territory). We found the responses as described in an earlier blog where Great Tits react very strongly to the songs coming from the wrong place and take in their stride songs coming from the right place. Great Tits know where their neighbours live and recognise their songs.

The territorial males responded in a very similar way to the songs of new neighbours and the songs of old (ie familiar) neighbours when played from the correct boundaries. We took this to mean that learning of neighbours’ songs wasn’t restricted to early life; Great Tits could learn the songs of neighbours every year of their lives (potentially) as new territorial males took over territories. Learning songs for neighbour recognition is not restricted to early life in the Great Tit.

Well, that’s quite interesting since learning songs for performing them is restricted to early life in most birds. You learn songs when young and sing them for the rest of your life. Whereas we showed that when it comes to learning your neighbours’ songs Great Tits seem to go on learning and remembering.

We noticed something which looked interesting, but wasn’t quite statistically significant (if only we’d had another one or two birds in the sample!). We noticed that the response to new neighbours’ songs when played from the wrong place, was weaker than the response to old neighbours’ songs and that seemed interesting.

It was as though Great Tits found it more difficult to get new neighbours’ songs correctly stored in their heads than old neighbours’ songs. You could speculate that those small Great Tit brains were, perhaps, full up with memories of old songs from old neighbours so that there wasn’t space for the new songs to get in quite as well. Fanciful perhaps, but this has a proper grown-up name; pro-active memory interference (where stuff that is in your head already stops you remembering new stuff). And I feel that my brain is a bit like that! Now it might work in a different way, retro-active memory interference, where new memories are stored well and they push out or interfere with the old memories. One could spend quite a long time in a pub with friends taking about which you all have and which is the most evolutionary sensible form of memory interference.

But we were lucky to have data with which we could attempt to examine which, if either, was the case in Great Tits. Actually luck had nothing to do with it.

To cut to the chase, it seemed from our data that there was a good case for pro-active memory intereference in song recognition by Great Tits; the more songs you had experienced over your lifetime, fom different neighbours in different years, the more difficult it was for a Great Tit to get his new current neighbour absolutely straight in its little head. Great Tits’ brains fill up with former remembered songs and make it a bit more difficult to learn new neighbours songs.

Now this study was done in 1984 and submitted for publication in 1985 (after trying Nature first and not getting in) and was published in 1986 by which time I was working for the RSPB and had a completely different set of research objectives, so I haven’t kept up with the literature. Maybe no-one has replicated our findings with any other birds and it’s of little importance, or maybe someone has pointed out some major error in our work, or maybe it’s seen as a bit dull and old hat because everyone knows that these days. I’ll try and find out for myself and let you know.

But this story, not the most simple story i know, does show how one can examine the natural world, in the field, experimentally, and get insights into things like brain function. And I think that is quite impressive (not that we were impressive but that the approach is impressive). And the ability to do this requires long-term study and recording of the right data – you can’t go back and assess the song types of a now-dead Great Tit. And I don’t remember that I had much input to this study except by helping out a mate – I probably lugged some of the equipment around and took some notes. But when I hear two Great Tits singing at each other, as I can as I write this, then I remember this study from 35 years back.

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