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Index of Subjects
Index of Subjects Hi Steve, Richard and others, Since athletes have been brought up in the discussion, here is a summary from the program Mythbusters on the Discovery Channel which tested whether eye black gave players an advantage or whether it was simply a myth. Explanation:In 1942, Washington Redskins' fullback Andy Farkas hit the football field with ash from a burnt cork smeared below his eyes. Today, these iconically sooty swipes have evolved into a variety of synthetic substances worn by football and baseball players alike. But does eye black really absorb light and prevent glare as some players suggest? The MythBusters put this smear campaign to the test to uncover eye black's visual advantage, using a light meter to measure its effectiveness. Turns out, indirect light does more than make players blink. It creates "veiling glare," which reduces their ability to see clearly. Wearing eye black won't keep this optical phenomenon from happening, but it can tone it down. The stripes improve the eye's ability to differentiate between light and dark, and that increased contrast means you can see in greater detail. The better you can see the minutia around you, the better you can track an object as its speed increases - which is obviously important to outfielders following a pop fly's sunward trajectory. Does donning eye black improve athletic performance? While the MythBusters can't blindly guarantee its effects are a game-winner, they can see one thing clearly: Eye black can give a baseballer's eyesight a definite boost. Given this finding I'd expect to see most of the raptors and aerial insectivores with black near the eyes. Many raptors do, particularly the bird hunters (e.g. the accipiters and falcons). However, immature accipiters don't have 'black' around the eyes. A number of aerial foragers also have 'dark' faces, though again there is often an age and even a male versus female difference. Perhaps it is enough to have dark areas under the eye as opposed to light or perhaps there are differences in the prey they exploit. However, many of the small flycatchers have white eye-rings which seems to be counter to what we would expect. The trait is also found in birds that don't specialize in catching prey on the wing (e.g. Black-and-White Warblers and Red-breasted Nuthatches who are primarily bark and leaf gleaners), though they do catch insects in flight from time to time. It could be that for many species this is an enhancement to vision, for others it's a courtship trait, for others it is disruptive camouflage and for some it may even be primarily to prevent feather wear (black areas of feathers are tougher than non-black areas). Or, it may be some combination of these. All the best, Lance Lance Laviolette Glen Robertson, Ontario lance.laviolette@lmco.com -----Original Message----- From: naturens-owner@chebucto.ns.ca [mailto:naturens-owner@chebucto.ns.ca] On Behalf Of Stephen R. Shaw Sent: Saturday, March 17, 2012 2:24 AM To: naturens@chebucto.ns.ca Subject: EXTERNAL: Re: [NatureNS] Article: Zoologger: Unmasking the Zorro of the avian world I had a look at this and while it's interesting as Richard says, it seems iffy, perhaps more on account of the treatment by the blogger than of the original authors. The first three 'straw man' ideas offered as to what function the bird's dark eye-stripe fulfills are pretty unconvincing from the start. This bird, a masked shrike, must either be somebody's favorite or just one that was readily available for study, because it doesn't have a particularly prominent eye-stripe. You could pick better birds, over here at least, for such a study (swallow family, two shrikes, both waxwings, black-throated gray warblers), that have much more completely dark eye-surrounding feathers. The idea eventually advanced in principle sounds plausible, that the dark feathers in the eye stripe help reduce the sun's reflection into the eye. This would reduce glare and so increase the visual contrast available to the shrike hunting insects, when perched facing into the sun and looking downwards. If that's the case, though, wouldn't you'd expect that the feathers ABOVE the eye would be black to reduce the sun's reflection, as in chickadees, or do the facial bones under the eye jut out a lot so you'd put the black pigmentation there too (as do AFL-ers)? Just having a dark strip running horizontally through the eye would not seem to be particularly useful for all this. Their test of painting the black feathers white to see if this worsens hunting skill (apparently so) is in the right direction, but using gouache paint that is known to contain white pigments (making it unusually white-reflective} may not be. This could easily have made the reflections much larger than those that would arise from having normal light-coloured feathers in that location -- not a fair test of the idea, unless they measured local light reflectance and controlled for this (not reported in the blog). Black feather pigments seem to be melanins, and I'm not sure if you could bleach these out locally, to retain the feathers' reflective textures but turn them whiter. Perhaps some of the birders here might know, if local bleaching has ever been used earlier to mark individual dark birds for identification. The glaring omission at least in the blog is that many birds have feather patterns that are known or believed to have species- and/or sex-recognition functions. That this has nothing to do with enhancing visual contrast seems obvious where there are pronounced sex-differences, with completely black headed or black-faced males at least in the breeding season, e.g. american redstart, both orioles, bay-breasted warbler. If the major advantage is to possess anti-sun-reflection eye surrounds for insect-hunting, you'd think that both sexes would have developed it and also retained it year round. Not so. Browsing through the warbler pictures in Peterson, an even more frequent feather pattern on the head is to have a supercilium/eyebrow that is white or light coloured. What could that do for vision? -- it would seems like a really bad idea, based on this report, but it is very common. A developmental hangover from the ancestral warbler (bottom of the barrel idea)? Has anyone in the bird world asked this question? Steve, Halifax ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Quoting Richard <sternrichard@gmail.com<mailto:sternrichard@gmail.com>>: > Interesting bird related article from the New Scientist > > Zoologger: Unmasking the Zorro of the avian world >