A few weeks ago Gus McNab was over and we were discussing spotlighting and I mentioned how I have a good population of Owlet Nightjars on our block but I never see them at night because their eyes don’t eyeshine, despite wandering the woods after hours. He told me (politely) how wrong I was and the issue was that I was not holding the torch in the right place to see it. What I needed to do was walk around like a unicorn with the torch beam emenenting from between my eyes. I (polietly) said that is faseniting, thinking that this was surely some ploy to make me look like an idiot…not that help is required…and thinking how that could possibly be true? Last night, I had a visiting bird-o who wanted to see Nightjars and other things so we decided to wander the tracks and see what we could find. First try was for White-throated Nightjars…two birds pearched up for us, brilliant eyeshine. A koala started calling back at the house so we wandered back, yep bright eye shine…we then decided to walk down to “owlet-nightjar grove” and I had three birds respond and two come in, one quite close. I put the torch on the bird and as expected no-eyeshine…but then I tried Gus’ recomendation and move the torch between my eyes and wow, its eyes shown back bright red like a Christmas tree. Amazing! Gus you were right, but I have no idea what the explanitaion was or why this is the case! Thanks for the tip…wanted to share publically. Cheers, Roger Roger McNeill Samford Valley, SEQ =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) to: birding-aus-request@vicnet.net.au http://birding-aus.org ===============================
Hello Chris, Thanks again for your interesting and detailed response. Now that you mention Jack, he gave a fascinating lecture on this subject to the folks at O’Relillys Bird Week some years ago – I have but a vague recollection of the detail – such is the joy of getting older! I do have a good picture of a Tawny Frogmouth in staring mode – I should annotate it appropriately. Cheers Graeme On 19/11/2013, at 9:41 AM, Chris Corben wrote: =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
Hi Graeme There’s an interesting aspect to this. The man to talk to is Jack Pettigrew, who has done a massive amount of work on the eyes of these creatures. I know he looked at Owlet Nightjars, but am not sure what he found. But because of my long involvement with Frogmouths, I do remember the story with them. They are apparently at least unusual in being able to swivel the eyes within their sockets. I thought Jack said this was very unusual in birds, but am not sure. But the case with Frogmouths is quite fascinating. Because they can swivel their eyes, they have two different modes of vision. In one mode, the eyes look out to the sides and then there is very little overlap, so their sight covers a very wide angle but without the bifocal overlap which gives a sense of depth. Like the vision you would expect of a Snipe! So this is well suited to looking for threats, but not for catching prey. In the second mode, the eyes swivel around to face the front, giving them a much narrower field of view but with broad bifocal overlap and good sense of depth. More like a Human or an Owl. If you watch a roosting Frogmouth in the daytime, you can see these modes very easily. Typically, a roosting Frogmouth perches in a very relaxed position, sort of like a Kookaburra in general pose. I am convinced they never sleep – certainly I have seen no evidence of it. They are constantly alert. If they see what might be a threat, they then strike the classic “broken branch” pose, where they stretch out their body and slim it down so it looks smaller and less conspicuous. In this pose, they watch you through one eye, looking out sideways at you and reducing the eye to just a slit, which isn’t very conspicuous, and I think is the reason people think they are asleep – because the eye looks shut. If you then walk around them, they follow you with very inconspicuous head motions – keeping you in view with one eye. But typically there will come a point where they suddenly turn to face you, swivel their eyes around and stare straight at you with both eyes, at which time they take on a look which is much more owl-like! I don’t know if an Owlet Nightjar can swivel its eyes. Cheers, Chris. On 11/18/2013 03:29 PM, Graeme Chapman wrote: — Chris Corben. =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
=============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
Water buffalo eyes also look blue and crocodiles are red. So if you’re walking through the bush in Kakadu and you see blue eyes then be careful (and yes, I have been in this position and it was a buffalo). Occasionally one can encounter a crocodile crossing land in the late dry season. So big red eyes, with a bit of distance between them, might be avoided as well. Barramundi eyes shine red too, by the way. Good to know if you’re fishing at night. Denise Denise Lawungkurr Goodfellow PO Box 71, Darwin River, NT 0841 043 8650 835 PhD candidate, SCU Vice-chair, Wildlife Tourism Australia Nominated for the Condé Nast international ecotourism award, 2004 by the natural history and cultural tourism American website, Earthfoot. Wildlife Adviser, BBC¹s Deadly 60¹ On 19/11/13 3:39 AM, “Chris Corben” < cjcorben@hoarybat.com> wrote: =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
You can see eyeshine on an incredibly wide range of insects and spiders. As with birds, and everything else I have seen an eye-shine from, the colour is dependent on the viewing conditions, particularly the angle from which you view it in relation to the subject’s head. The colour may also appear to change with how close you are, but that might be just a perception thing. However, it is usually obvious that some things differ in colour in typical viewing conditions. A Greater Glider or a cat typically look very bright and greenish, while most possums look more red, orange or yellow in most conditions. Typical Nightjars look very bright, but distinctly orange-reddish. Frogs when viewed well usually look whitish or pink. Sheep look more blue. Interestingly, Owls, Frogmouths and Owlet Nightjars generally don’t look very bright, despite that they are very nocturnal. There is a huge difference in eyeshine brilliance between a typical Nightjar and a Frogmouth! Cheers, Chris. On 11/18/2013 06:57 AM, Andrew Hobbs wrote: — Chris Corben. =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
Ooops. As Philip Veerman reminded me (at least to me), arachnids are not insects of course . So while I had thought that their eyes are compound eyes, in fact they have multiple simple eyes or ocelli. Andrew On 18/11/2013 8:08 PM, Andrew Hobbs wrote: — *********************************************************** Andrew Hobbs pardalote@iinet.net.au *********************************************************** =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
Given the nature of insect eyes, is it possible that you are seeing some sort of irridescent effect, similar to the irridescent colours seen in some insects and bird feathers etc. (due to diffraction, multiple reflections and interference etc.) Andrew On 18/11/2013 7:03 PM, Denise Goodfellow wrote: — *********************************************************** Andrew Hobbs pardalote@iinet.net.au *********************************************************** =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
On 18/11/2013 3:23 PM, Peter Shute wrote: I don’t know about Owlet-nightjars. The fainter red colour would suggest not, (Although some animals have a Tapetum Lucidum layer that gives a bright reddish shine) but that seems a bit strange in a bird that is supposed to be nocturnal. Perhaps most of its activity is crepuscular, and there has been less selective pressure to develop or maintain the structure. Alternatively perhaps the evolutionary line lost or didn’t gain the ability to produce the structure in the past. The Owlet-nightjars are a group which appears to have evolved rather early on in the evolutionary history of birds. They are certainly not closely related to the owls or nightjars; groups which do appear to have a Tapetum Lucidum layer. Phylogeny of the owlet-nightjars (Aves: Aegothelidae) based on mitochondrial DNA sequence John P. Dumbacher, Thane K. Pratt, and Robert C. Fleischer Molecular Phylogenetics and Evolution 29 (2003) 540–549 at http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.61.2950&rep=rep1&type=pdf Andrew — *********************************************************** Andrew Hobbs pardalote@iinet.net.au *********************************************************** =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
And wolf spiders’ eyes (for that’s what you’re seeing), appear to change colour as you approach them! Denise Denise Lawungkurr Goodfellow PO Box 71, Darwin River, NT 0841 043 8650 835 On 18/11/13 6:24 PM, “Mona Loofs Samorzewski” < mona@loofs-samorzewski.com> wrote: =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
Thanks Andrew for that excellent explanation. Along the same vein, I have walked around the bush at Howard Springs near Darwin at night with a head torch on, and seen many many reflections coming from the ground from spiders eyes. And they were blue! A friend with a hand-held torch wasn’t seeing them at all until he put my head torch on. And then we realised how many spiders we were walking on… Mona On 18/11/2013, at 4:54 PM, Andrew Hobbs wrote: and for the same reason. =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
So Owlet-nightjars don’t have this Tapetum Lucidum? I assume putting the torch closer to your eyes to help see the fainter shine uses the same principal as moving a camera flash further from the lens to reduce red-eye. Peter Shute Sent from my iPad =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
As an aside to this topic – Does shining a bright light into an animal’s eyes do any damage to the eyes? John Wooroloo WA —–Original Message—– [mailto:birding-aus-bounces@lists.vicnet.net.au] On Behalf Of Andrew Hobbs Sent: Monday, 18 November 2013 1:55 PM There are two types of ‘eye shine’. As Chris said it is partly simple physics. By the nature of the eye and its focus on the back of the eye when light is shone into it there is a reflection from the back of the eye. As is the case with anything being illuminated, at least some of the light is reflected back along the same path and will appear to cause the eye to ‘shine’ (compared to the rather non-reflective coat of hair, feathers etc). But there is another factor. Some animals (including some birds such as owls) which are active at night, have a layer at the back of the eye called a ‘Tapetum Lucidum’. This layer contains mineral crystals which have the property of reflecting almost all the incident light back along the same path as the incident light. (Look up ‘Corner reflector’ on Wikipedia) This layer is behind the layer of light sensitive cells, doubling the sensitivity of the eye. (The cells have two chances of capturing photons; coming and going). When you shine a light into an animal or bird with these eyes they really do appear to shine very brightly. However the reflection is not perfect and some light is reflected back somewhat ‘off axis’. In this case, because the reflection is so strong, you can still see a reflection even if your eyes are well off the same axis as the torch beam. In contrast, in animals (and birds) without a Tapetum Lucidum, the light is reflected of the Fundus at the back of the eye. This is not a good reflector but some does get reflected back along the axis. Because the reflection is so much weaker your eyes need to be much closer to the axis of the torch beam to see the effect. The colour of the eye reflection from the Tapetum Lucidum depends upon the properties of the crystals in the layer. It can vary more or less across the full visible spectrum. However in animals without that layer the reflection is always red. The red colour is mainly due to the haemoglobin in the blood vessels at the back of the eye. (This is the basis for the red eye effect in people. We don’t have a Tapetum Lucidum.) Andrew On 18/11/2013 12:18 PM, Chris Corben wrote: — *********************************************************** Andrew Hobbs pardalote@iinet.net.au *********************************************************** =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org =============================== =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
There are two types of ‘eye shine’. As Chris said it is partly simple physics. By the nature of the eye and its focus on the back of the eye when light is shone into it there is a reflection from the back of the eye. As is the case with anything being illuminated, at least some of the light is reflected back along the same path and will appear to cause the eye to ‘shine’ (compared to the rather non-reflective coat of hair, feathers etc). But there is another factor. Some animals (including some birds such as owls) which are active at night, have a layer at the back of the eye called a ‘Tapetum Lucidum’. This layer contains mineral crystals which have the property of reflecting almost all the incident light back along the same path as the incident light. (Look up ‘Corner reflector’ on Wikipedia) This layer is behind the layer of light sensitive cells, doubling the sensitivity of the eye. (The cells have two chances of capturing photons; coming and going). When you shine a light into an animal or bird with these eyes they really do appear to shine very brightly. However the reflection is not perfect and some light is reflected back somewhat ‘off axis’. In this case, because the reflection is so strong, you can still see a reflection even if your eyes are well off the same axis as the torch beam. In contrast, in animals (and birds) without a Tapetum Lucidum, the light is reflected of the Fundus at the back of the eye. This is not a good reflector but some does get reflected back along the axis. Because the reflection is so much weaker your eyes need to be much closer to the axis of the torch beam to see the effect. The colour of the eye reflection from the Tapetum Lucidum depends upon the properties of the crystals in the layer. It can vary more or less across the full visible spectrum. However in animals without that layer the reflection is always red. The red colour is mainly due to the haemoglobin in the blood vessels at the back of the eye. (This is the basis for the red eye effect in people. We don’t have a Tapetum Lucidum.) Andrew On 18/11/2013 12:18 PM, Chris Corben wrote: — *********************************************************** Andrew Hobbs pardalote@iinet.net.au *********************************************************** =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================
Roger It’s very simple physics. Almost anything looks brightest when the light source is close to your eyes. But in addition, a bird’s eye is pretty much retro-reflective. That is, the light reflected by it mostly goes back along the path it came from. If you think about it, you are looking at the inside of a sphere, so wherever the light comes from, it is reflected back in the reverse direction. The same principle is used to make road markings shine brightly at night. The paint on a road is filled with tiny glass spheres, so that from whatever direction the light arrives, some portion of it is retro-reflected. Since the headlights of a car are not too far off the line of your sight, a lot of that light comes back to your eyes, and the markings look bright. If the paint was just plain gloss paint, it would be much more reflective, but nearly all the light from the headlights would be reflected away from the driver, and the paint would look essentially black. As does smooth ice, and for the same reason. Owlet Nightjars eyes are not nearly so bright as White-throated Nightjar’s eyes. But even a White-throated can be seen at much greater distance with a light which is close to your eyes. It makes such a difference, that you can wear a headlamp and see the eyes of things like owls at reasonable distance even though the headlamp is not very bright. A side benefit of this is that the lower light levels will scare the bird a lot less, so you can actually gain by having a lower intensity light if it is close to your eyes. A headlamp is perfect for that! Incidentally, if you know to look for it, you can see eye-shine of animals in all sorts of unexpected ways. A classic case is to get to a place where there are frogs on the surface of the water. If you get the sun straight behind you (eg in early morning or late afternoon), you will be able to see their eye-shines surprisingly well, especially if you use binoculars. Using binoculars with a headlamp is a great way to find all sorts of creatures at night. Frogs, snakes, geckoes, spiders, small mammals and even bats in the right situations. Just use your binoculars to look at the spot of light from the headlamp. Cheers, Chris. On 11/17/2013 08:39 PM, Roger McNeill wrote: — Chris Corben. =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) http://birding-aus.org ===============================