Hi Ted, et al.,
Good question! While like David said bats often fly irregularly and
the wrong direction, Some nights, especially later in the night, most
of the bats I see are all going the right direction and flying
directly. Because I am using a scope I can ID them ok, but now that my
3 year old daughter is into moonwatching with me I only get use of the
scope some of the time and use my binoculars when she is watching. I
quickly realized how many birds are missed and how dificult it is to
tell a bird from a bat at a lower magnification. I tried both 8 and 10
power bins and although the 10s were better, I could not always detect
birds my daughter was seeing and/or definitely assign bird/bat. So
that sparked the next experiment , different zoom levels on my scope.
It makes sense, but I saw more birds at 60x than at 20x. Also again,
more birds with a polarizing filter on the end, this was also easier
on the eyes. So where does that leave us? Well definetly we need much
more thought of optics used and how to assign some type of detection
probability. I have some ideas on how to do this, Ted you might be in
a good position to immediately test this with your class this wekend!
Anyway, something to ponder as we gear up to do this on a larger scale.
Talk to you all soon,
Mike
Sent from my iPhone
On Sep 4, 2009, at 6:30 AM, David Mozurkewich
<[email protected]> 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
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