One of my favourite animals that I only discovered existed recently has to be the happy wren. Not only is it happy (just look at this photo), but it also duets with its partner in such a synchronised way that they are often mistaken for a single bird.
Have a listen to this recording of its song:
It sounds like a single bird, but in fact it's two birds. From this sonogram below you can see how this 'looks': the two birds alternating between each other, so fast that it sounds like a single bird singing. One bird is denoted by the blue line, the other by the red.
In some duetting birds, like the green woodhoopoe or the stripe-headed sparrow, the male and female sing together in unison. This is impressive, but cannot compare to birds that alternate between each other to sing together. The parts that they sing need to be correct not only in their ‘tune’, but also in their timing to the millisecond. Such antiphonal duets are so quick, that to the human ear it can be over in a few seconds and we can’t even distinguish the two birds without the help of technology. If this weren’t complicated enough, the phrases that these duetting birds sing often differ in how long they are, and the birds can also be far apart from each other.
If that weren’t impressive enough, each male and female may have thirty to forty different phrases that they sing, that they have to combine together in their duet to form a song that is specific to that partnership. No wonder these birds are so happy; they are masters of composition.
But how do these birds coordinate such a refined and complex achievement? To find out, Chris Templeton and colleagues caught male happy wrens in Mexico, and played them recordings of their female mates singing. They did this by recording the pair duetting out in the field, and then erasing the male’s part of the song from the recording. They changed the distance and the speed of the female song, to see how the male would adjust his song to compensate and keep the 'duet' going smoothly. This is a bit like a human singer slowing down and speeding up, and the piano accompaniment having to keep up and match their pace without making it too obvious to an audience.
The male happy wrens sang back to the recordings of their females, and matched their singing speed to the speed of the recording. The males were also more likely to respond to the recording of the female singing when it was closer to him than when it was further away. This could be either because it’s harder for him to duet at a longer distance, or because he didn't want to advertise the fact that his mate was far away from him to other males that might be listening.
What’s really impressive is how quickly the male happy wrens responded to the recording of their mate: half of the males sang back to the recording on their very first time listening to it. They also tended to sing the correct phrase type that matched the females’ phrase (of their thirty to forty different phrases they knew) as well as matching her speed. This is impressive. Within a fraction of a second the male identifies not only that this is his female singing (without being able to see her), but also which song she is singing and then responds appropriately.
However, males did not always stick to their phrase that matched the female recording, and it seems likely that this is because he was attempting to lead her into singing a new song (perhaps frustrated with the fact that of her thirty plus songs she has available, she ‘insisted’ on singing the same one over and over again). When the recorded female failed to switch to his new song, he conceded and went back to singing the recorded one. This implies that the male may lead singing, but is also attentive to what the female decides to sing.
Photo Credit: all photos by Chris Templeton
Reference: Templeton, C. N., Mann, N. I., Ros-Cheln, A. A., Quiros-Guerrero, E., Macas Garcia, C., & Slater, P. J. (2013). An experimental study of duet integration in the happy wren, Pheugopedius felix. Animal Behaviour. 86: 821-827