I have a bunch of photos from reader Stephen Barnard of Idaho, but he has sent a largesse of red-tailed hawks (Buteo jamaicensis). So here’s a special post with those photos, one of which provides a lesson about evolution.
His note:
The second photo shows the nictitating membrane.
I can’t resist pointing out that humans carry the vestigial remnant of a nictitating membrane from our ancestors in the form of the plica semilunaris in the corner of the eye (full nictitating membranes are absent in nearly all mammals except monotremes and marsupials). Go look at your plica semilunaris in the mirror now! Spread your eye as in the diagram and look in the corner by the nose. That’s the remnant of the nictitating membrane that your reptilian ancestors had. (Some of you who are less evolved* will have a more pronounced remnant.)
Here’s a photo of what to look for:
The hawk with the membrane retracted:
*only kidding, but I like to joke about that with the students
I’ve been in windstorms when a nictitating membrane would have come in handy.
Your photos are a marvel to behold. I keep sharing them with my teens. Thank you!
Ain’t that the truth.
Beautiful shots as always, Stephen.
I remember looking at my eye in a mirror as a child and noticing it – just thinking it was kind of cool. I’m glad to learn that it is something really cool.
Dogs have a remnant of the membrane as well. My vet pulled my dog’s once and I can especially see it if I waken her suddenly.
And the nightmare inner eyelid on a cat D:
Here’s a closeup of crocodile eye in action
oops, sorry about the embedding, didn’t mean to do that
Cool
Actually, I think it’s perfectly relevant in this case. Thanks for posting it.
¡Ai caruncle!
Heh heh
Had a look. I must be the missing link.
I love the colors of their plumage. There are a few Copper’s Hawks that live in my neighborhood. We have a real problem with non-native bird species (non-native species of all kinds really) in South Florida and it’s really exciting to watch these hawks hunt ring-necked doves and parrots. But the Cooper’s Hawk just isn’t as pretty as his red-tailed cousin.
Very cool. I wonder if the membrane can stay shut like an eyelid or if it’s always reflexive like a blink. I also didn’t realize the membrane was so opaque, or maybe that’s just something to do with the lighting. The crocodile’s is more transparent.
I find the first hawk photo very intriguing. First time I’m getting a good look at how the feet are closely tucked in flight. Thanks for the great work, Stephen.