March Recordings Revisited: A Compilation of the Calls for Easier Listening, Interesting Knocks, and Some Additional AnalysisPosted: December 10, 2017
If you’re interested in possible double knocks, I’ve made what may be some important new finds, so be sure to read the whole post and listen to the clips at the end.
In the meantime, I think this post will be of interest to many readers – from the new ones who’ve found the blog either because of the recent sighting or after reading about Project Coyote on the LABird list (thanks to Jay Huner for the mention) to other ivorybill searchers and aficionados to those who have had trouble hearing the putative ivorybill calls on the March recordings or didn’t want to wade through all the audio.
In the easy listening department, Steve Pagans has made a compilation of the clearest calls on Matt Courtman’s first, 2 hour clip recorded on the morning of March 15 using NCH software.
I tweaked Steve’s version a bit, amplifying it and applying noise reduction using Audacity, an equivalent program. Sonograms were generated using Sonic Visualizer, to my knowledge the best free program of its kind.
Both Steve’s version and mine (immediately below Steve’s) should make it considerably easier to hear many of the calls recorded that morning. Steve’s is somewhat cleaner, and mine is somewhat louder.
Steve’s extracts from Matt’s first clip:
With additional amplification:
Steve has done similar, shorter condensations of the the other two recordings Matt made. (The extract from the second clip adds little, so I’ve opted not to post it.)
Steve’s extract from Matt’s third clip:
With additional amplification:
The calls have a very consistent sonogram pattern (the stacks of three or more parallel horizontal lines), with an emphasis on the second partial (third horizontal line from the bottom). There are apparent tree squeaks in both clips that have a similar quality; the dominant frequency is similar, but the tree squeaks show more energy at that frequency. The second screen cap is a detail of the first, showing both calls and tree squeaks. The latter show a brighter orange, indicating more energy at a similar frequency to the calls’ dominant partial. The sounds are definitely different, but they can be hard to distinguish at the margins.
Steve’s effort, which took many hours, inspired me to revisit the recordings and specifically to reexamine possible responses to Matt’s anthropogenic double knocks and Phil’s playbacks over the course of the more than three hours when Matt’s recorder was running. I had concluded that the ADKs did not seem to have had an impact, but on careful re-listening, I’ve amended that view. Matt’s knocks do seem to have stirred up calls in reaction and to have generated several possible single or double knocks.
Listening through the recordings and especially to the ADKs and their immediate aftermath was a time-consuming and difficult process, especially because the knocks are very loud and tightly spaced. Matt used two wooden blocks (rather than dowels and a tree trunk or a knock box) and did not follow a specific protocol. Overall, his approach was more aggressive than Frank’s or mine, both in terms of volume and number of knocks, and a somewhat more restrained approach is probably advisable in the future. Nevertheless, if you assume (as I do) that ivorybills were present on this morning, these recordings may provide some insights into the efficacy (or lack thereof) of ADKs in generating responses.
This return visit to the recordings also supported my view that the putative ivorybill calls (recorded in the old search area) that Phil played back generated no reaction at all from the suspected ivorybills on the morning of the 15th. Blue Jays, however, appeared to respond, and I now tend to think those calls (though not all of those recorded in the old area) were Blue Jay, based on the apparent Blue Jay responses and on the harmonics. In retrospect, it’s unfortunate (but totally understandable under the circumstances) that playback of the Singer Tract recordings and other possible attraction methods weren’t tried. Perhaps another opportunity will present itself, although the events of March 15 were singular . . . thus far.
In the first of these two clips, the playback seems to have provoked Blue Jays to call faintly. In the second, in which the Blue Jay calls are easier to hear, they had been calling before the playback began.
By my count, Matt did 7 sets of ADKS and performed approximately 205 knocks in all. I noted six possible double or single knock responses (of varying quality) in four of the six series. These knocks occurred within seconds of ADKs. The temporal proximity between the ADKs and the possible DKs and SK in response make it less likely that Matt and Phil (to a lesser extent) would have noted them in the field.
I’m posting the relevant extracts below in unmodified form followed by clips with the interesting knocks amplified using Audacity. They should be audible through a desktop computer, but headphones will help. To repeat a strong caveat: Matt’s ADKs are very loud (which made this analysis especially difficult). I should also reiterate that I don’t consider myself particularly skilled at analyzing recorded knocks; I don’t have the greatest ear for intervals and have no direct field experience with Campephilus woodpeckers; my ability to interpret sonograms is also limited. Nevertheless, I’m sure these sounds are neither shots nor industrial noise (or duck wingbeats). With one exception (the fifth knock, which sounds like a single to me), I’m also confident that Matt was not the source of the sounds. Some of inadvertent bumping together of his blocks should be audible at various points, and it has a different quality.
The first set of ADKs was the shortest, involving only six, and these were very closely spaced. The first ADK in the series produced a possible DK in response. Matt began the series 15 minutes and 52 seconds into the recording, and there had been a kent call at 14:59. Both a possible DK and a kent call can be heard between the first and second knocks. An additional kent can be heard after the third knock (omitted here).
I did not find any possible double knocks in the second and third series, and there were only a few kent calls – one during the second and three during the third. There was a possible double knock in the fourth series, at 1:48.22, two seconds after an ADK.
During the 5th set, on the second clip, I found a possible single knock at 3:16. (Steve Pagans, who has an excellent ear, thinks it’s a closely spaced double.) I can’t rule Matt out completely as the source of this sound, but I think that’s a remote possibility.
Edited to Add: Playing the clip at a slower speed, reveals that there are two distinct knocks, the first louder, and leaves me convinced that Matt was not the source of this sound.
Also on the second clip in the 6th set, there’s a possible double knock at 30:26, approximately 2 seconds after an ADK.
On the final recording, during the 7th and final set, there’s possible DK after the 5th ADK in the series. It was preceded by a possible ambient DK about 50 seconds before Matt began the ADKs. The ambient knock is slightly buried behind some rustling, approximately three seconds into the recordings. To my ears, the DK in response sounds as though the first knock is softer than the second, something that’s uncommon but not unheard of for Campephilus woodpeckers. I’ve included both the entire relevant sequence and extracts in which I’ve amplified the knocks.
Unmodified clip with ambient DK and later DK in response to Matt’s 5th in a series of ADKs:
Ambient DK Amplified:
Amplified DK in response to ADK:
Finally, in listening to parts of Matt’s first clip again, I noted that there are a number of very distant kents. These are barely audible at normal volume and only faintly so on the amplified version. This suggests a highly mobile source (or sources) for the calls. It also suggests that there may be more calls on the recordings than the approximately 200 hundred I originally estimated. Steve noticed these calls too but elected not to include them in his compilation because the amount of amplification necessary degrades the sound quality. Thus, it may be difficult for some readers to hear these more distant calls.
The first few seconds of the extract below are unamplified to give a sense of the volume of other ambient sounds at the time. The kent calls come toward the end, and with one partial harmonic showing up faintly on the sonogram (the lighter colored dot near the left margin in the image below).
Amplified Distant Kents:
I owe readers the final installment of the “Bits and Pieces” series (hotlink is to the most recent installment). I anticipate that it will be my final post for this eventful year. Look for it just before Christmas.