Bird song (7) – Great Tits (2)

Forty years ago, in early April 1980 I helped my boss Dr John Krebs (now Prof The Lord Krebs of Wytham Woods, FRS) to finish off a field experiment looking at the function of bird song. Bird song is thought (I would say known, actually) to play important roles in both territorial defence (in birds that have territories) and mate attraction. Our experiment looked at the role of Great Tit song in mate attraction (indirectly).

John and his previous research assistent, Richard Cowie, had started this experiment in 1978. It consisted of temporarily removing the female from a pair of Great Tits and seeing whether the male responded by increasing its rate of singing. We conjectured that it would if song played a part in mate attraction. And, spoiler alert, it did!

All you need to do this experiment is a colour-ringed population of Great Tits, some peanuts or sunflower seeds, a mistnet, some ears, a notebook and a stopwatch. We had all of those things in Higgins Copse which is a detached outlier of Wytham Woods close to the Oxford western ring road and where the Oxford-Swindon road leaves Oxford – I often glance towards the wood as I pass that way all these years later.

We listened to an individual Great Tit singing and recorded how much he sang for a while, and then captured his mate at a bird feeder and popped her in a holding cage, recorded how much the focal male sang in the absence of his mate and then released the female and recorded the male’s song again. We recorded the number of times the male sang, the amount of time that he sang, and which song types he used. And we did this for eight different males. And, for five of them, we recorded the singing behaviour of a neighbouring male at the same time.

When the female is removed from the territory the male goes ballistic – his song rate increases 6-fold. When the female is returned then the song rate drops back to close to normal almost immediately. The males whose females weren’t removed didn’t change their singing much. The simplest explanation for this (we discussed other explanations in the paper) is that the male notices that his female has gone and immediately wants to attract a new mate. This is the breeding season after all! This explanation was supported by two of the males actually attracting new mates during the experiment and dropping their song rate pretty quickly.

There are lots of other studies that would back up this, and ours wasn’t the first or the best study, but it was one of the first experiments in the field to look at this matter.

In the real world, presumably Great Tits do lose their mates to disease, starvation and predators, and so males need a way to get another nesting attempt underway. Are they callous? That’s not a very sensible question in terms of evolution by natural selection.

Were we callous, to carry out this experiment? Not very, I’d say. It mimicked a natural phenomenon and it was about as callous as a detention is in a school context.

This study is a small brick in a big wall, it isn’t the wall and it isn’t the biggest brick, but it’s a brick.

For me, 40 years ago, it opened my eyes to the possibility of answering scientific questions with experiments in the field, where one wasn’t holding a test tube and wearing a white coat, but had binoculars around one’s neck and was holding a stopwatch and a notebook.

But if your Great Tit, in your garden, starts singing at a high rate all of a sudden then it might be that he has lost his mate, or he may be having a fight with another male Great Tit, or there may be something else going on. Birds are amazing.

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7 Replies to “Bird song (7) – Great Tits (2)”

  1. If you removed my female, I’d go ballistic as well.
    On the other hand, when I pick up my guitar in the evening she clears off to bed!

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  2. A clever and callous-free experiment. (OK, if there is any callousness it's in a worthwhile cause and carefully controlled)
    Thanks for the interesting science. Bird song is free and amazing.

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  3. My female has removed herself for a couple of days, gone off to Cardiff to help her daughter with the grandchildren.
    So I walked the dog this morning, on a dull cold wind day there were 4 Song Thrushes, a Mistle Thrush, Chaffinch and Nuthatch singing. The best thing however was a pair of Ravens courting in the top of a conifer some distance away.
    When ay university we used a Krebbs book "Introduction to behavioural ecology" although I always thought the Colinvaux book "Why big fierce animals are rare" the better title.

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  4. Of course he may also be trying to fool his neighbours in to thinking there are already many birds about, the Beau Geste hypothesis.

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    1. I believe the beau geste hypothesis does not seek to explain the rate of singing but rather why males have a repertoire of songs: by singing a number of different songs it creates the illusion of a number of different males singing and therefore, hopefully, persuades other males thinking of taking up residence that the site is already fully occupied and defended and that they are better off moving on. In the book Beau Geste the the defenders of a desert fort that is under attack, prop up their dead comrades with rifles to trick the enemy into believing the fort is still well defended.

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