THE DRUMBEATS DO IT….
April 13th
Capercaillie tracks with my glove for size © Chris Hails
These past two weeks have seen a sharp rise in temperatures and what little snow remained on the Jura has now gone, so this past weekend I decided to visit again a location I know holds Capercaillie, and last month I had seen their tracks in the snow. Despite two pre-dawn visits over the weekend I did not get a glimpse or a sound of them, they are both shy and scarce and the Jura population is in decline, mostly due to forestry and tourism disturbance I think.
Last month (27th March) I was able to record a Green Woodpecker drumming - an uncommon event. This time I also had some luck in recording a Black Woodpecker (Dryocopus martius) (Pic noir) drumming, something I have heard before but have not been able to record, in this piece I have shortened the time between the drums and it was a very windy day so there is a lot of noise from the trees in this recording, but you can still get an impression of the loud noise this large woodpecker makes:
The following day was still devoid of Capercaillie but at least it was not as windy. This time for amusement I recorded two Great Spotted Woodpeckers (Dendrocopos major) (Pic épeiche) hammering out a contest with each other (and there must have been a third which you can just hear calling around 25 seconds) - the different drumming posts they have selected create a higher and lower note:
So all this drumming that was going on made me think that it would be interesting to compare the three alongside each other, so in this next piece I have joined my three recent acquisitions together, the first two drums are Great Spotted, the second two Black and the third two a Green Woodpecker:
There is no point to discuss the tone (whether high or low) of the drum as that clearly varies according to the nature of the branch being used and its ability to resonate, but if we look at the frequency of the beats the differences between the birds become very clear:
GREAT SPOTTED WOODPECKER: the bursts ares fairly short, the two bursts took only 0.66 seconds and 0.72 seconds respectively for 14 beats which works out at about 20 beats per second, this can be seen in a screenshot of the waveform of one burst, notice also that the amplitude (loudness of each beat stays fairly even throughout.
Waveform of Great Spotted woodpecker drumming - each large spike is a blow on the wood and its amplitude is an indication of the volume (loudness) of the sound. Bottom axis shows time in seconds
BLACK WOODPECKER: the bursts are much longer - 2.36 and 2.52 seconds respectively, but each of the two was a consistent 19.5 beats per second, very much like the Great Spotted frequency, but maintained for longer. Notice also the steady diminution in amplitude giving the impression of the drum "fading out" slightly.
Waveform of Black Woodpecker drumming - note the longer time and the steady diminution in amplitude creating the “fading out” effect.
GREEN WOODPECKER: I am showing both of the sequences here to show something of the erratic nature of the beats, each had about 15 beats in it, the first at 16 beats per second and the second at 12 beats per second, and of course this is a much weaker sound (I amplified the waveform a lot so that you can actually see the beats), it really is quite unlike the other two, and as Gorman (2004) says it is altogether "not very convincing and rather weak".
Waveform of Green Woodpecker drum - a very different pattern of irregular beats with variable and generally weak amplitude.
This analysis is based on rather small sample sizes of course but begins to illustrate some of the things to watch out for or to help identify drumming if you hear it. I will add to this as I collect more drumming from other woodpecker species. In Gorman (2004) you can find a more detailed discussion.
Juvenile Great Spotted Woodpecker study © Frank Jarvis
