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Sand Piper In Flight (ID Help), Bonelli Park, LA County (1 Viewer)

RafaelMatias

Unknown member
Portugal
I agree, Spotted Sandpiper. Interesting that there's only one reflection.

Yep, that caught my eye as well. The bird on the right hand side is not in the same plan as the other one, it's closer to "us" (out of focus) and its reflexion falls below the photo frame.
 

Microtus

Maryland USA (he/him)
Supporter
United States
Yep, that caught my eye as well. The bird on the right hand side is not in the same plan as the other one, it's closer to "us" (out of focus) and its reflexion falls below the photo frame.

Ah. I thought it was slightly further away than the reflective bird.
 

Deb Burhinus

Used to be well known! 😎
Europe
It is a nice capture but my geometry-challenged female brain is trying to work out the optical illusions here. I get that the out of focus bird is at a different depth of field to the focussed bird. Can a nearer bird of the same size really appear so much smaller through digital zooming - we know it can but the fact the reflection is below frame (as Raphael astutely pointed out) suggests the bird is actually a lot nearer than I would imagine even with artefact. It therefore offers unusual visual proof that resulting size difference from this effect can be considerable (especially pertinent when you think we use size so often to determine and distinguish shorebird/wader etc IDs from digital photo.).

The other visual ‘confusion’ I have is, if I’m seeing it correctly, the reflection is somehow reflecting the upper wing pattern - how does this work? Is the wave higher than it looks and we are somehow seeing a refection on the trailing surface of the wave but the digital zoom has ‘flattened’ it? The angle of the bird flying just doesn’t seem acute enough from the horizontal to produce an upperwing refection?
 

RafaelMatias

Unknown member
Portugal
It is a nice capture but my geometry-challenged female brain is trying to work out the optical illusions here. I get that the out of focus bird is at a different depth of field to the focussed bird. Can a nearer bird of the same size really appear so much smaller through digital zooming - we know it can but the fact the reflection is below frame (as Raphael astutely pointed out) suggests the bird is actually a lot nearer than I would imagine even with artefact. It therefore offers unusual visual proof that resulting size difference from this effect can be considerable (especially pertinent when you think we use size so often to determine and distinguish shorebird/wader etc IDs from digital photo.).

The other visual ‘confusion’ I have is, if I’m seeing it correctly, the reflection is somehow reflecting the upper wing pattern - how does this work? Is the wave higher than it looks and we are somehow seeing a refection on the trailing surface of the wave but the digital zoom has ‘flattened’ it? The angle of the bird flying just doesn’t seem acute enough from the horizontal to produce an upperwing refection?


Re your first point, there are a few papers/short notes even on birders magazines dealing with this illusion, which is real and it's explained by optics and physics; I can try and dig them out (but not much time during the next few days), because I cannot recall the exact reasoning, but as far as I can recall, the higher the magnification the stronger the illusion (most evident on telescopes, etc).

Re the 2nd point: imagine the bird was banking to the other side, showing the belly and underwing: would you expect to see the upperparts on the reflexion? ;)
 

Deb Burhinus

Used to be well known! 😎
Europe
Re the 2nd point: imagine the bird was banking to the other side, showing the belly and underwing: would you expect to see the upperparts on the reflexion? ;)

Well wouldn’t that depend on where I was standing? o:D

- seriously though, it looked as if the mantle and far wing was facing the sky so I was trying to work out how it could be reflected in the water at the same time - now you mention it, it’s obviously banking at a steeper angle than I first thought :gh:
 

RafaelMatias

Unknown member
Portugal
Agree - looks the more distant of the two to me too; smaller in measurement in all dimensions, so even despite optical illusions, it has to be the more distant.

Michael, if it were more distant the reflection would show up on water. It's that "detail" that shows where the bird is in space.
 

THE_FERN

Well-known member
Re your first point, there are a few papers/short notes even on birders magazines dealing with this illusion, which is real and it's explained by optics and physics; I can try and dig them out (but not much time during the next few days), because I cannot recall the exact reasoning, but as far as I can recall, the higher the magnification the stronger the illusion (most evident on telescopes, etc).

Re the 2nd point: imagine the bird was banking to the other side, showing the belly and underwing: would you expect to see the upperparts on the reflexion? ;)

how about paper linked here:

https://www.birdforum.net/showthread.php?t=393040
 

THE_FERN

Well-known member
I get a "not found" message in British Birds page when clicking there, but that was one of the papers I was thinking of, exactly. British Birds used to have their papers available for free, but not anymore it seems; I noticed that when looking for another paper some days ago.

EDIT: crossposted with Deb

Weird. I accessed this about a week ago...

[Edit: you can pop the URL into to internet archive wayback machine and get from there (a generally useful trick)]
 
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RafaelMatias

Unknown member
Portugal

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