Nice data Mike! The relationship looks intuitive to me. Here's my broadly-general speculation on the topic: Under stable atmospheric conditions, I think you get less flight calls during initiation of migration than you do once birds are at altitude. The rationale is that birds don't really 'need' to communicate initially since they've just departed and presumably know what they're doing (plus there is still a small amount of ambient light available to them(?)). If there's heavy fog, or the conditions aren't really good but birds are migration-ready, or they're being pushed offshore, you might experience a lot of call activity just after sunset... otherwise, I think it's usually less. As birds gain altitude and call more, the detections increase but only to a point, after which the probability of detection begins to fall and you're just not picking them up. Then as they descend, the detection increases again AND they may be calling more frequently as they're planning to settle in for the following day... and may even be communicating with birds already on the ground. Now if some of the acoustic researchers could chime in with some actual data supporting or refuting this, I'll go back to working on the radar ;)
good listening! David ________________________ David A. La Puma Postdoctoral Associate Aeroecology Program Department of Entomology and Wildlife Ecology University of Delaware Visiting Scientist SILVIS Lab (http://silvis.forest.wisc.edu/) University of Wisconsin, Madison Teaching/Research Profile: http://www.woodcreeper.com/teaching Websites: http://www.woodcreeper.com http://badbirdz2.wordpress.com On Fri, May 11, 2012 at 8:26 AM, Lewis Grove <[email protected]> wrote: > Hi Andrew and all, > > Automated detection of calls is a tricky business, though it is relatively > easy to figure out the proportion of calls that you are actually pulling > out - just count calls manually, screen by screen and then see how many > your detectors find. We looked at 90 different random 15-minute segments > from three different recording sites, using multiple observers to find the > total number of calls present. > > Basically, depending on the software package and the parameter > combinations you use (SNR and occupancy are the big ones other than having > your time and frequency bounds correct), you can get wildly different > proportions, ranging from near zero to near 100% of calls. I can't > remember the exact numbers but I believe Tseep-x finds something just shy > of 50% of the warbler/sparrow calls present in a file. Other factors come > in to play here too - background noise (insects) particularly. > > Hopefully all of this data (there's a lot) will someday see the light of > day in a journal - it's overdue. > > Lewis > > > On Fri, May 11, 2012 at 8:19 AM, Andrew Albright < > [email protected]> wrote: > >> Mike - I enjoy reading your reports, so keep 'em coming! >> >> I'm no expert, but I think when I asked the question before it seems >> that the general idea is that nfc are easier to detect in the first >> couple of hours and then around dawn as birds will be flying at lower >> elevations (and they can get so high that you can't detect nfc). But >> I don't know how much data supports this hypothesis and it's quite >> possible that it's from East Cost migration which could be >> significantly different from that seen in Texas. >> >> I have one question - have you ever gone through an hour or a night of >> your data to see/hear how well the automatic detection works? >> Also, what % of nfc can you not assign to a certain species? >> >> Sincerely, >> Andrew >> >> On Thu, May 10, 2012 at 4:15 PM, Mike Farmer <[email protected]> wrote: >> > Since March 1, our Austin city station has recorded 4250 night calls. >> The >> > quieter station 10 miles to the west had 6372. See the attached graph >> > showing the number of calls per hour of the night. This is for the >> quiet >> > station. >> > >> > This chart seems rather too convenient. I am suspicious of it. What is >> > known about this kind of timing? The curve matches the inverse of the >> > relative quiet of a typical night. Life is just quieter in the middle >> of >> > the night. So can’t a lot of this be a detector and noise effect? >> Or do >> > the birds actually fly and call more in the middle of the night? >> > >> > Also this data doesn’t adjust for daylight savings shift in the third >> week >> > of March or the fact that dusk shifts to later times as spring >> progresses. >> > What we really want to plot is the hour after dusk not the actual >> time. But >> > has anyone here figured out a formula for the number of minutes each >> night >> > that dusk shifts? You can google this and get a bunch of graphs but >> there >> > must be a formula ..... probably involving a bunch of cosines and other >> > witchcraft? >> > >> > -Mike Farmer >> > >> > >> > equipment >> > >> > Mic – Oldbird 21c >> > >> > Software – Oldbird tseep, thrush, GlassOFire, Raven Pro, Excel >> > >> > -- >> > NFC-L List Info: >> > Welcome and Basics >> > Rules and Information >> > Subscribe, Configuration and Leave >> > Archives: >> > The Mail Archive >> > Surfbirds >> > BirdingOnThe.Net >> > Please submit your observations to eBird! >> > -- >> >> -- >> >> NFC-L List Info: >> http://www.NortheastBirding.com/NFC_WELCOME >> http://www.NortheastBirding.com/NFC_RULES >> http://www.NortheastBirding.com/NFC-L_SubscribeConfigurationLeave.htm >> >> ARCHIVES: >> 1) http://www.mail-archive.com/[email protected]/maillist.html >> 2) http://www.surfbirds.com/birdingmail/Group/NFC-L >> 3) http://birdingonthe.net/mailinglists/NFCL.html >> >> Please submit your observations to eBird: >> http://ebird.org/content/ebird/ >> >> -- >> >> > > > -- > Lewis Grove > PhD Student, Wildlife Ecology > President, Graduate Student Association > SUNY *E*nvironmental *S*cience and *F*orestry > (814) 880 - 5667 > > > -- > *NFC-L List Info:* > Welcome and Basics <http://www.northeastbirding.com/NFC_WELCOME> > Rules and Information <http://www.northeastbirding.com/NFC_RULES> > Subscribe, Configuration and > Leave<http://www.northeastbirding.com/NFC-L_SubscribeConfigurationLeave.htm> > *Archives:* > The Mail Archive<http://www.mail-archive.com/[email protected]/maillist.html> > Surfbirds <http://www.surfbirds.com/birdingmail/Group/NFC-L> > BirdingOnThe.Net <http://birdingonthe.net/mailinglists/NFCL.html> > *Please submit your observations to eBird<http://ebird.org/content/ebird/> > !* > -- > -- NFC-L List Info: http://www.NortheastBirding.com/NFC_WELCOME http://www.NortheastBirding.com/NFC_RULES http://www.NortheastBirding.com/NFC-L_SubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/[email protected]/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/NFC-L 3) http://birdingonthe.net/mailinglists/NFCL.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
