Can the moderator PLEASE end this thread?
On Feb 17, 2016, at 12:34 PM, Jennifer Miller <foundnatureblog@xxxxxxxxx> wrote:
Tom's comments about the human eye got me thinking, so I decided to look
around a bit.
I consider the lights from urbanization
different from a direct light like flashlights and flashes.
I no longer have access to a university library and most research papers,
but
I did find some interesting comments posted by
prominent
researchers
(Drs. Jack Pettigrew and Graham Martin)
on
an Australian
bird listserv
. Also included was a photographer's experience
:
http://photo.net/learn/nature/owlflash
Another site had information for nature photographers:
https://www.naturescapes.net/articles/health/flash-photography-and-the-visual-system-of-birds-and-animals/
And the last was the personal recommendations of a photographer for
photographing owls:
http://www.mackerrowphoto.com/night-photography-of-owls
The general gist
of these
being that the researchers think it
would
take 30 - 60 min for eyes to fully adapt to darkness again.
Vision begins to return within the first 5 minutes, but it does take
longer (general consensus is an hour) for vision to be fully adapted to the
dark again.
Generally no permanent damage was observed by the researchers, but caution
should be used because they could be more vulnerable to predation during
this time and the risk to each species should be assessed based on its
normal
behaviors. There was one unfortunate story of a photographer
'
s flash causing a
n owl
to crash into a stone
wall and fall a considerable distance
,
causing serious injury to the bird.
The message I keep coming across is that the cost
s
should be weighed against the benefits and that nesting and nocturnal birds
should only be compromised if the picture will be of
public
educational value.
I would love to learn more about how the eyes of birds work, but I am
traveling at the moment.
Jennifer
Jennifer Miller
Lubbock, TX
{o,o}
/)_)
" "
Email -
Foundnatureblog@xxxxxxxxx
Blog - http://foundnature.weebly.com/index.html
On Feb 15, 2016, at 2:47 PM, Ervin Fleming <endersgt@xxxxxxxxxxxxx> wrote:
My degree is in Astronomy. Observational Astronomy emphasizes the function
of the human eye. The accepted time for full dark adaptation is 25 minutes.
However, stepping into the dark from a lighted room only requires 3-4
minutes for functional adaptation (walking around without killing
yourself). Most of the enhanced vision of night predators comes from the
special layer just above the retina which captures some of the light that
bounces off of the retina and reflects it back to the retina. So their
retina would have roughly the same sensitivity as ours without this aid.
Bottom line: only a very few minutes is needed to return to a retina
without after images. If adaptation was a real issue with night hunters,
they would shun the developed areas due to the high number of intense light
sources. As with other animals, avoiding the cities is no longer an option.
Additionally, the elevated ambient light levels in the urban areas may be
of use to them. I hope this puts your mind at ease a bit.
Tom Fleming
Grand Prairie
On Monday, February 15, 2016 1:12 PM, Jennifer Miller <
foundnatureblog@xxxxxxxxx> wrote:
I was recently watching a documentary about WWII and they talked about how
pilots would have to sit in the dark for up to an hour until their eyes
fully acclimated to darkness. When I see photographs of owls taken at
night, I always wonder how long it takes for their eyes to adjust back to
the darkness and worry about the disruption to their hunting and normal
activities, especially during nesting season. Personally, I avoid even
spotlighting an owl with a flashlight, but does anyone know if bright
flashlights and photography flashes disrupt an owl's normal behavior for a
significant amount of time?
I see lots of discussion about the ethics of using playbacks on the
listserv, but not about using lights on owls.
Thanks for your thoughts,
Jennifer
On Sun, Feb 14, 2016 at 7:56 AM, David McDonald <dkmmdpa@xxxxxxxxx> wrote:permission
Hi Texbirders,
We all know how familiarity sort of breeds laziness. I did not have a
photo of a Barred Owl in the wild yet, despite it being a backyard
bird which I hear at least once a week. I always figured I would find
one roosting in the daytime, but of course I never did.
I read in a birding magazine how to tape a high intensity LED
flashlight to your lens for night photography. So I prepared my camera
before Christmas and this winter I was going to get a photo!
Well I awoke about 4:30 and heard a pair of them hooting in the yard.
I took the camera out and found them on a branch about 20 feet up. I
turned the flashlight on but it wasn't bright enough to focus with the
autofocus and I am horrible on manual. I went back into the house and
set the ISO to 5000 and tried again. One bird was still there. Still
not enough light. Grrrrrr
I went back in, got the tripod and another flashlight. Back outside,
he had flown about 30 feet up in the tree, and I had to go way back to
tilt the camera up on the tripod and hold the flashlight along with
lens as well.
Eureka! I got him. This first one is with his head forward looking a me.
http://www.pbase.com/davidmcd/image/162567426
Here is a side view and can see the spotting on his wings and all of his
tail.
http://www.pbase.com/davidmcd/image/162567427
And lastly he fluffed his wings and his legs are showing - very thick
and strong looking. I think he could carry of one of my cats.
http://www.pbase.com/davidmcd/image/162567428
Another bird off my bucket list :)
Good birding,
David McDonald
Friendswood TX
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