[obol] Re: Nictating membrane?
- From: "Jenkins, Maurice A." <alanjenkins@xxxxxx>
- To: "canyoneagle@xxxxxxxxxxx" <canyoneagle@xxxxxxxxxxx>, 'OBOL' <obol@xxxxxxxxxxxxx>
- Date: Sun, 6 Jul 2014 21:20:37 +0000
Lori,
I think the peregrine is showing its closed outer eyelids, not the nictitating
membrane, and it's in the first stages of sleep---maybe a short nap. During
the day at a time when the Oregon days are long and warm and the kids are
ever-hungry, what's a harassed Mom to do?
Here's a link I found with Google to a peregrine brooding its young with its
eye(s?) closed:
http://www.wqed.org/birdblog/peregrine-faqs/question-why-are-her-eyes-white/
and it resembles your great photos.
I conducted a time-lapse photographic study of nesting Gyrfalcons in Greenland
for my M.Sc. thesis. This was done with super-8 movie film because the only
digital equipment in 1973 was one's fingers and thumbs and they are a base-10
system.
I set my cameras, which continually took 1 frame each minute, on 2 Gyrfalcon
nests during the nesting season. There was enough light at that latitude in
the summer to be able to read inside my tent 24 hours a day; so, I was eager to
know if the falcons slept at "night." Later in the lab, from the developed
film, I observed that the first stage of sleep was for the incubating or
brooding adult (usually the female did those duties) to close both eyelids.
The Gyrfalcon's eyelids are covered with short white feathers, down feathers I
think, but I don't know that for sure. Slowly the falcon's head would droop
slowly and end up resting on the nest substrate, a raven nest at one site, soil
substrate at the other. The last phase would be for the bird to turn its head
over one wing and rest the head on its back, tucking the beak into the dorsal
plumage above the vertebrae. These stages went back and forth from one to the
other. I assume that Gyrfalcons and Peregrine Falcons have very similar sleep
behaviors. Some of the sleep behavior that I describe can be seen in digital
camera snapshot frames here:
https://www4.uwm.edu/letsci/biologicalsciences/falcon/peregrine-falcon-information-2013.cfm
One has to scroll through various frames of other subjects to find them.
Regards,
Alan Jenkins
Creswell, Oregon
________________________________________
From: obol-bounce@xxxxxxxxxxxxx [obol-bounce@xxxxxxxxxxxxx] on behalf of L
Markoff [canyoneagle@xxxxxxxxxxx]
Sent: Sunday, July 06, 2014 9:54 AM
To: 'OBOL'
Cc: canyoneagle@xxxxxxxxxxx
Subject: [obol] Nictating membrane?
While on the coast last week I took a few photos of a Peregrine at Yaquina
Head. When I downloaded the photos I noticed its eyes looked odd. I am
guessing this is due to its nictating membrane being engaged. If not that,
then can anyone tell me what is going on?
Photos here:
https://www.flickr.com/gp/canyoneagle/X0Df8n/
And here is a tidbit I found on the topic of nictating membrane from The
Peregrine Fund:
For additional protection, raptor eyes are equipped with not one, not two, but
three eyelids. Two of their eyelids are just like ours; they move up and down
to close their eyes. The third eyelid is known as a nictitating membrane, and
this is the eyelid they use to blink with. It is a thin, semi-transparent lid,
which moves from side to side. Closing and opening it helps keep their eyes
moist and clean. When closed, it also helps to protect the bird’s eyes but
still allows some vision. Raptors might close their nictitating membrane when
feeding their chicks, when making contact with their prey, when in a fast dive,
or even during a heavy rainstorm. An osprey closes its nictitating membrane
when diving into water after fish - just like we might put on a pair of water
goggles before plunging in to a pool.
Lori Markoff
Eugene
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