As discussed here: How would a Reflecting-Oven-Jay Evolve?

The Reflecting-oven-Jay

This is a small African predatory bird with a perfectly smooth set of wings with an area of ~100 cm2, so maybe the size of a pigeon. It hunts in large flocks, around 10,000 birds to a group (there are plenty of real birds that form flocks this size). Using some basic multiplication, this flock can focus about 130 kW of sunlight. The flock decides to kill and eat an elephant, who has a metabolism of around 3000 watts and already has to work to keep cool on a warm day (heat sink ears, spraying water on self, etc). By spreading out and focusing sunlight on the elephant, the birds totally overwhelm the elephants ability to cool itself, raising its body temperature by about a degree Celsius every 2 minutes (130 kW / 4 tons*specific heat of water), leading to slow heatstroke and death. Divided evenly, there's a lb of meat for every bird in the flock, a huge windfall, sustaining the group though any cloudy days until the next kill.

Assuming it evolved as described in the answers to that question, is this actually viable?

We've seen birds self-organize into vast flocks so creating a formation should be achievable but:

How much light could an individual Jay actually concentrate into an area?

Can the flock manage to scale that up to a sufficient power to overheat the target?

Do the birds need to land and use their wings and tails as reflectors (in which case they'd need the right shaped for the land surface) or can they do this while in flight. While in flight would be ideal as it makes them considerably more terrifying.

On the bright side (all puns intended) the fact that they are doing this in an already extremely hot area and aiming at animals already coping with high temperatures does count in their favor. They don't need to raise the temperature very much.

  • $\begingroup$ If there are enough of them (and certainly flocks of 1000+ birds are not uncommon) they don't all have to be constantly aiming at the target to keep enough heat on it to continually raise its temperature. I would think it would just take some clever formation flying so that at any given moment ~70% of them are focused. $\endgroup$ – thanby - reinstate Monica Apr 24 '15 at 11:24
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    $\begingroup$ I get the feeling we keep thinking of them reflecting sunlight with the wings or back or tail. I saw them more akin to hummingbirds (and being able to fly while staying in one place - hovering - and thus using the feathers on their chest/bellies becomes possible. - Not sure if thats actually more viable, but it's how I saw it. $\endgroup$ – Spacemonkey Apr 24 '15 at 14:43
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    $\begingroup$ @Seth They need to reflect a lot of light though, bills wouldn't have enough surface area. $\endgroup$ – Tim B Apr 24 '15 at 15:32
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    $\begingroup$ Another problem is that we have birds which flock together to hunt and take down a target. Why use the slow and uncertain process of sun reflection when they can just all claw and talon the elephant in a swarm? I can't even imagine how the poor elephant defends itself other than swinging its head and hopefully knocking some with its tusks/trunk $\endgroup$ – DoubleDouble Apr 24 '15 at 21:49
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    $\begingroup$ There are real-world creatures using combined heat (from their bodies) to slow-cook animals larger than themselves. Japanese honey bees vs giant hornet: youtube.com/watch?v=K6m40W1s0Wc (warning, flashing lights!) $\endgroup$ – Neil Slater Apr 25 '15 at 7:05

My attempt doesn't truly answer if it is feasible or not, but it does try to come up with a believable solution.

The problem is flight

If this bird indeed developed this behavior through survival, we can almost immediately discard any notion of it using it's reflective feathers while on the ground. Not that birds are necessarily all slow on the ground, some are very fast (ostriches), but from an evolutionary historical standpoint, birds than are very fast on the ground, aren't in the air, and vice-versa. Not to mention ground predators don't necessarily need to see as much in order to pounce on their prey if it's on the ground. So our bird is a good flyer. But how can a flying bird reflect sunlight. A bird in flight will normally hold itself almost horizontally. Meaning feathers on its back, wings, head, and tail would reflect light upwards (mostly) and the ones underneath would have no sunlight to reflect. This makes directing light reflection rather inefficient for most.

A bird with unusual flight abilities

The hummingbird is the only bird I know of that can hover. (You can read up on it on Wikipedia). It also needs huge amounts of food and is basically constantly fighting starvation because it spends too much energy but let's get back to the question at hand. Hovering allows for more precise placement in a defined space. It also allows the bird to position itself much more vertically, meaning there's an actual non-dynamic surface (belly or back&head) that can now reflect effectively sunlight towards something. Add the ability to place itself properly and a flock of hovering birds could form some kind of a reflective panel formation, using up to 20-30% (invented number) of their surface to reflect light.


Another idea lacking on information about how feasible it is.

Imagine if the birds had tails like a peacock branching behind them. Except less wispy, more reflective.

White Peacock

You could make them ground based, but the scenario seems to indicate that flying is better.

So instead, for birds in flight, imagine if the tail moves not only up or down, but can tilt from side to side. This will interfere with their flying, so either the wings need to overcome the drag from the tail or the bird actually glides from its tail (which overcomes the drag from the wings) while using its wings to reflect the light, though that causes some amusing images of gliding birds in my mind.

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    $\begingroup$ Peacocks have to close their fans when they fly- too much drag. (It's not tail feathers: the fan is grown halfway down their backs where they can amass enough muscle to erect it.) Also, a fan can't give the aerodynamic shapes for flying. $\endgroup$ – Zither13 Apr 25 '15 at 7:36
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    $\begingroup$ @Zither13 +1 Good information! $\endgroup$ – DoubleDouble Apr 27 '15 at 15:43
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    $\begingroup$ I'm not necessarily recommending a peacock flying with its fan open, but a bird with a horizontal fan (which can be supported by the air/wind itself if not by muscles) that is either smaller and can be tilted while the bird flys normally or larger and provides gliding capability while being able to reflect using its wings. $\endgroup$ – DoubleDouble Apr 27 '15 at 15:43
  • $\begingroup$ I like the ground based solution, just for the opportunity to watch the elephant try to charge them! $\endgroup$ – Cort Ammon May 26 '15 at 15:04
  • $\begingroup$ @Zither13 is correct about the fan not being the tail feathers, they're the tail coverts. The tail itself is used to lift them, however. See this photo $\endgroup$ – Draco18s no longer trusts SE Jun 23 '17 at 15:35

Mythbusters did an episode trying to use solar power to repel a pirate ship (at the behest of President Obama). They found one major challenge is aiming. If you're the only one putting a jittery bright light on the target, it's easy to see your errors and correct them. With 10,000 jittery bright lights, it becomes hard to determine which one is yours, and good aim was very difficult. They solved it by putting a mesh in front of the mirror-holders so that each mirror holder could see where their light hit the mesh, and extrapolate out to the ship.

Accordingly,to aim, the oven-jay would probably need to have a special limb which reaches out in below the oven-jay and acts like a targeting recticle (or like Mythbuster's mesh). The oven jay would need to calibrate this geometric structure, and then ensure it doesn't change during flight (which is not easy for any organic structure).

Also worth noting would be that the path of an oven-jay would be very predictable during attack, because it would have to hold its wings at a very exacting angle. Oven-jays would have to fear predators from above while they are attacking. An attack could take a very long time. Consider the heat of 13 1kW space heaters, and think about how long that would have to be focused to actually kill an elephant. The ovenjays are only 10x faster than that.


They could be a two-step reflector akin to a mirror telescope: the huge swarm flies below, reflecting and focussing the sunlight upwards, and a small swarm flies above, reflecting and further focussing the light through a small hole in the lower swarm. They could circle all the while, which would also fit the inclination needed for the focussing

enter image description here

Note that both mirrors would be bowls, which would roughly fit the way the birds would need to angle their wings for flying in circles.

The different mirroring might be sexual dimorphism, one gender is mirrored on the upside (and therefore make up the lower mirror), and one gender would be mirrored on the underside to populate the upper mirror.

The leisurely circling would also alleviate the need for perfect focus: They could keep this up for hours, while the elefant would exert itself trying to get away.

I thought about the circling and the angles of the wings some more: If the oven-jays fly in circles around the axis of the telescope, the wing angles (angle of bird vs. horizontal) for birds near the axis would be more greater (because the curvature of the flightpath would be tighter), while the mirror actually needs to be more horizontal there. This could be solved by having them all fly in similar ellipses, thereby setting the parts of the flightpath with higher curvature (and therefore steeper wing-angling) farther from the axis, and the parts with less curve and less wing-angling nearer to the axis. Center of the ellipse would be the axis.

Flight-paths seen from above

Pictured: Flightpaths as seen from above

  • $\begingroup$ Interesting idea, it does solve several of the problems with getting the reflection angles right at the cost of increased complexity. $\endgroup$ – Tim B Apr 13 '18 at 22:49
  • $\begingroup$ This is what I was thinking, but while the end result would certainly work better it's also much more difficult to explain how it evolved. That being said if you started with a bird prone to circling over dying animals (vultures) it might make more sense that they discovered how to do this. $\endgroup$ – adaliabooks Apr 16 '18 at 9:52
  • $\begingroup$ re: the evolution of this mechanism, you do not need to evolve it as a predatory tactic from the get-go. Just as the mammalian immune-system (a mind-bogglingly complex construct), it might have gotten kickstarted as the confluence of several features that evolved as something different (courtship, thermal regulation, camouflage/mimicri, foraging behaviour,...) and only then begun evolution as a coherent feature. $\endgroup$ – bukwyrm Apr 16 '18 at 11:58

No, as written it does not work, spacemonkey is right flying and reflecting do not realistically combine. And even in ground you would probably need to be stationary for some time, a state also known as "predator attractor".

I could expand on what spacemonkey explains about the reasons, but instead I'll just tweak the ****** birds to something that might work and maybe even evolve.

It is all about heat management. Assume a bird that evolves to reflect as much heat as it can. Make the feathers in wings transparent to sunlight in a further effort to reduce heat while flying. Would also give the bird lower visual profile while flying, making it harder to recognize by both predators and prey. And even if the predators sees the bird making the wings harder to makes predicting its evasions harder.

Now imagine a huge flock of these birds. Sunlight streams down thru the transparent wings of the flock or reflects off their white bodies. It hits the ground below and a large part of it converts to heat. But the flock reflects the resulting infra-red back creating essentially a mobile greenhouse under it.

This behaviour could evolve since the resulting updraft would make flying easier, if the bird forms flocks for some other reasons. And yes being surrounded by these birds would make you hot, provided it was tropical midday. So heat exhaustion might happen and be usable as weapon. Large flocks of these birds could drive off competition from carrion simply by hovering around until the competitor must leave. From that it is a short step to using the the heat to create new carrion. The special effect is very different from what you probably wanted, though.


An idea not touched upon yet is flying in a group around the target.

While flying light can easily bounce off the wings and make the whole idea of focusing the light into the target hard. Standing on the ground to do the same is also just as hard due to threat from predators.

So my take on it would be: the back and tail feathers are reflective and this focuses the light onto the target as they circle it. So, no hovering is involved and all light should, if at the correct angle, focus into the target as they go around it.

  • $\begingroup$ this decreases the overall area though, beacuse they would have to reflect the sunlight in a very flat angle, akin to x-ray telescopes - those also have far more mirror-surface than actual gathering-area $\endgroup$ – bukwyrm Apr 13 '18 at 22:34

The birds won't be able to stalk and kill a large beast with their ability. Aiming will be nearly impossible during flight, and landing on the target allows for many ways of retalition. Also, by hitting an elephant by about two degrees every minute, the elephant will have plenty of time to hide under the shade of trees, or to go into a river where the water will be a heat sink.

Your birds could hunt in some other way. In Australia every living creature is trying to kill every other living creature in one way or another, and sometimes they get creative. Australian birds of prey have taken a page from Cave Johnson and learned to burn other animals' houses down. Your birds could do the same thing, but they don't need to find a fire. They can make their own. Just burn the savannah high grass.

This has a lot of advantages:

  • A single bird can start a fire that will spread through a large area;
  • Not only there will be more meat than the birds can eat, it will be cooked, making it easier to digest. Same thing happened with hominids when our ancestors tamed fire;
  • This method of hunting is delightful to watch (I am not a pyromaniac).

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