there are already too many Davids on this list... ;) if you check out that moonwatching vid I posted, you'll see that indeed the bad was moving in the right "general" direction, and the only way I told it from a bird was based on the cadence of the flight, plus when I viewed it on the big screen you could make out the forward appearance of the wing, etc.
What David is talking about, though, can be seen in this really cool paper by Sid Gauthreaux and John Livingston (http://tinyurl.com/m7q2t5), where bats especially show more erratic flight on thermal imagery. But, when moonwatching, given prevailing winds, bats which are not actively feeding could (and probably do) move in the same direction as birds, and insects definitely will move with the prevailing winds. Most of the separation, then, falls on the observer, and as Mike pointed out, magnification may be the key. good moon watching David ____________________________________________________ David A. La Puma, Ph.D. Dept. of Ecology, Evolution, & Natural Resources Online Teaching Portfolio: http://www.woodcreeper.com/teaching Lockwood lab: http://rci.rutgers.edu/~jlockwoo Websites: http://www.woodcreeper.com http://badbirdz2.wordpress.com Photos: http://www.flickr.com/photos/woodcreeper On Fri, Sep 4, 2009 at 7:31 AM, Erik Johnson <ejoh...@tigers.lsu.edu> wrote: > David et al., > > All the birds are flying the same direction while other critters have > random flight paths. > > Is this really a safe assumption? Last night I did some moon watching > and the majority (just barely) of birds were headed westish. But > others were flying south, some northeast, etc. I was fairly confident > these were birds and not bats, but Mike made a good point about optics > (I was using 10x binocs) and wasn't videoing so I have no way to prove > to myself (or you guys) what I was seeing. In any case, I checked out > the radar and there was decent volume, but the radial velocity had a > trend of movement to the SW, but with a lot of scatter. Again, were > these birds? I think so. Perhaps variation in the direction of > movements is more apparent where I am along the gulf coast where > topography and bird ecology (water-crossing avoidance vs not; > trans-gulf vs circum-gulf; etc) significantly alter the behavior of > individual birds. I can imagine that farther north birds are pretty > much bombing south (although no doubt topography and ecology are > important there, too). I have had similar experience listening to > call notes - where you can pick out birds going in all directions. So > I think this phenomenon is real, at least here. > > Happy listening, > Erik Johnson > S Lafayette, LA (~40mi N of the Gulf of Mexico) > ejoh...@lsu.edu > > > > > > On Fri, Sep 4, 2009 at 5:30 AM, David > > Mozurkewich<moz...@bellatlantic.net> wrote: > >> On Fri, 2009-09-04 at 02:53 -0600, Ted Floyd wrote: > >> > >>> I should think that, given distant and fleeting views of such animals, > >>> there's the potential to over-count birds by accidentally counting bats > >>> and moths. Any pearls of wisdom on this one? > >> > >> Ted, > >> > >> All the birds are flying the same direction while other critters have > >> random flight paths. This eliminates most false alarms and is good > >> enough except when the birds are a minority of your detections. > >> -- > >> David Mozurkewich > >> Seabrook, MD USA > >> > >> > >> -- > >> NFC-L List Info: > >> http://www.NortheastBirding.com/NFC_WELCOME > >> http://www.NortheastBirding.com/NFC_RULES > >> > >> http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html > >> -- > >> > > > > -- > NFC-L List Info: > http://www.NortheastBirding.com/NFC_WELCOME > http://www.NortheastBirding.com/NFC_RULES > > http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html > -- > -- NFC-L List Info: http://www.NortheastBirding.com/NFC_WELCOME http://www.NortheastBirding.com/NFC_RULES http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html --
