This year I decided to make an attempt at getting into the Halloween spirit with this Great Horned Owl image. I think this birds “blown” eye contributes to the effect.
1/400, f/7.1, ISO 400, 500 f/4, 1.4 tc, natural light
This adult was actually preening but I thought the combination of the somewhat unusual pose with the open beak and red tongue was appropriate for Halloween.
And then there’s that “blown” eye (notice that the pupil is not round).
In my experience the incidence of blown eyes (atypical shape/appearance of the pupil relative to the rest of the visible eye) is unusually high in owls, though I have seen it in one adult Bald Eagle (scroll down to the 12th photo). I speculate that the following factors may contribute to the seemingly high incidence of this condition in owls:
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most blown eyes are caused by injury (I assume) during aggressive encounters with prey or other animals. GHO’s in particular are known for their aggressiveness
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owls have unusually large eyes which might make them more vulnerable to injury
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owls tend to hunt in low light which may make injury more likely
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owls tend to have brightly colored corneas and their eyes are large and conspicuous so the shape of their pupil is easier to see than it would be in birds with smaller, dark eyes
Some of this is speculation on my part. Others may have more informed explanations for this condition in owls and other birds.
Happy Halloween!
Ron
Glad to hear that you are on the mend.
And yes, this owl does have the Halloween look down pat. Thank you.
Thank you Elephant’s Child, for your comment and your ongoing concern.
Of course I have to chime in here … the ‘blown’ eye is actually termed an ‘anterior synechia’ – basically there’s been a injury, and some kind of damange or scar tissue has created an adhesion of the iris to the cornea, effectively pulling the pupil out of a true circle. Sometimes the pupil constricts fine and looks normal when constricted, but you see the synechia more when it dilates. Or the opposite – the adhesion can keep the pupil from totally constricting. Light still enters the lens and hits the retina, but they don’t have as much control as they would normally. Owls have voluntary control over their constriction/dilation – and if you watch carefully, you’ll see the pupil size change when neither the overall light nor the angle of light has changed. They constrict and dilate as they look at things up close or further away. When I have an owl on my glove, the pupils can turn into pinpricks as they see something well beyond my vision! They also can have pupils of unequal size – so you can’t use the typical test one uses in humans to see if they have a concussion. Depending on any other damage the eye may have sustained (for which the synechia might be the lingering, long term effect), their vision may or may not be compromised.
About half the owls we get into rehab (and owls make up 60% of what we see) have been in collisions with vehicles. Some of your hypotheses might be correct, Ron – but add in collisions as a much higher probability than encounters with prey or other animals. In fact, you’ll see that owls (and other raptors) close their nictitating (third) eyelid just as they go to attack something, in order to protect the eye from dust or other injury. The size of the eye makes them prominent but they also have a much larger bony sclerotic wing around the eye than other raptors, which helps protect them… and the cornea is amazingly tough! The eyes of nocturnal/crepuscular owls (and other nocturnal critters) are larger than diurnal birds, as you mention, for extra light gathering power – but they are remarkably well-suited for low-light conditions, so the fact they are moving around in those conditions should not lead to a higher probability of injury – that would not lead to the evolutionary success owls have attained, when you think about it. Although, like any bird, they see better in the light than in the dark, they have a much higher percentage of rods (black/white) than cones (color) than most birds and can utilize low light conditions brilliantly. Hawks and eagles get hit by cars also, but somehow it seems that more owls are hunting alongside the road or crossing low.
When you next have a light-eyed owl in your view, watch the pupils dilate and constrict. It’s truly fascinating the control they have.
Thanks so very much, Louise – this is EXACTLY the kind of stuff I’ve wondered about for a long time, ever since first noticing these blown eyes in owls several years ago and also since I became aware of the amazing control owls have over their pupils. I knew that they did it, but didn’t know many of the details you’ve provided.
I assume that when you’re talking about “collisions” as a cause of these injuries you’re not just talking about collisions with moving vehicles but with stationary objects like fences, etc. Many of my observations of owls with eye injuries (including blown eyes) have been with birds resident in remote areas with virtually no traffic. For example, three of the GHO’s I’ve seen with eye injuries have been on our remote Montana farm (the bird in this post is one of them) where there is no traffic of any consequence and one of those birds was a youngster that may not have even fledged yet. At the time I thought that the eye might have been injured by live prey (large Richardson’s Ground Squirrels) brought by one of the parents.
Thank you once again, Louise. Fascinating information – so glad you “chimed in”.
They can of course collide with stationary objects – windows, for example, as well as fences (although I haven’t personally seen this kind of eye injury from fences – they are usually barbed wire rips and tears, including of the eyelid, but mostly doing horrific damage to the body and wings) [barbed wire is right up there with lead shot/sinkers in my personal Book of Things I Would Ban if I were in charge of the world!] But I’ve also received a screech owl who hit the rear end of a pick up truck, which was going about 10 mph on a gravel road, so hard he blinded himself in both eyes. sigh. I hadn’t thought of struggles with prey causing this kind of blunt trauma – I would think that would more likely end up with corneal tears and abrasions, which can scar, certainly, but those look different from the synechias. But I could also be way off base there!
Thanks for coming back on this once again Louise.
The young bird I mentioned with the eye injury wasn’t necessarily a synechia. The bird kept its eyelid closed because of the injury so I couldn’t actually see the eye but the eyelid was obviously swollen and traumatized. Who knows what actually happened…
Very intimidating!
My thoughts exactly, Naomi.
Great photo, thanks! Any chance the blown eye is gender related? If I remember correctly, research of Black Oystercatchers indicated blown eye most often correlated with the females.
I don’t know, Nala, although I seem to recall reading something about exactly what you mention in oystercatchers.
Thank you to all those who have commented so far. I’m glad you like the shot and hope you have a fun Halloween.
On another note, several have inquired about my recent health problems. I just got back from the ENT specialist and it turns out that I’ve had a plugged salivary gland, causing significant pain and swelling in my neck and jaw. I’ve been out of sorts with it for several days but it finally seems to be resolving itself and hopefully it won’t reoccur. Thanks for your concern.
Ok, enough about my health. Back to birds…
It’s a sensational shot Ron! Thanks for sharing!
Charlotte
Happy Halloween Ron !
Oops RON!
Cool ron! Very SPOOKY. The lightness in the wood really adds to the shot.
I love how you capture these extraordinary moments! It’s a wonderful Halloween post.
It works. Scary! And beautiful too. Great light, really nice composition.
It does give the owl an “odd” look!