I wrote about birds and mirrors a while ago, and not much has changed scientifically since then. Most bird species tested have interpreted their own reflections as other individuals, responding either with aggression or courtship. Female pigeons who view their own reflections ovulate, apparently interpreting their reflections as suitable mates. Among birds, only magpies, so far, have been demonstrated to understand that the mirror reflects their own image, although pigeons can be trained to use spatial information from mirrors correctly in the real world.
So why bring this up again? Recently I saw a Yellow-rumped Warbler interacting with its reflection in a car side mirror, and took a video with my phone. Here it is (apologies for the lack of zoom):
At the time I took the video, I didn’t think much of it beyond general amusement. But rewatching it, I began to have some questions.
If the warbler interprets the reflection as another warbler, why does it attack? In the breeding season, another bird might merit some aggression, but it’s winter flock season here; the warbler was in a flock of other yellow-rumps at the time, and certainly did not respond to every glimpse of its flockmates with an attack. And why does the warbler keep going back to the mirror? It can’t see the reflection when it is perched on the mirror, as it is after each attack; it could easily interpret the vanishing of its opponent as the opponent’s having fled, and leave victorious. It can’t be going back to the mirror out of loneliness; the tree directly above it is chirping full of its fellows.
Some birds, given an option between a mirror and a view of an actual other live individual, prefer the mirror; the researchers suggested that this is because the mirror-bird’s behavior is predictable, but I wonder if there isn’t more going on here. We know most birds don’t understand mirrors—but perhaps they do understand that there is something off about them. The warbler in the video looks around after each scuffle with its reflection, as if looking for the mirror bird. Could the birds’ preference for their reflections—the warbler’s repeated returns to the mirror—be curiosity? A desire to return to a stimulus that doesn’t match the animal’s previous experience, and figure it out?
Clearly, a single warbler video does not a dataset make, and I’m not currently in a position to test any of this properly. But I’m going to pay more attention now to any birds I see interacting with their reflections. If you’ve ever seen a bird with a mirror, let me know in the comments what you think.
Reference
Derégnaucourt S, Bovet D. 2016. The perception of self in birds. Neuroscience & Biobehavioral Reviews 69:1-14.
Tough Little Birds 
Maybe it’s because it’s own reflection looks like a BIGGER bird than it has encountered before as things look closer than they really are (I.e. amplified) & it either feels threatened by the bigger bird or feels it needs to assert its own superiority over the bigger bird, or thinks it’s protecting the flock in the tree above from the bigger bird. I don’t really know, but just some thoughts.
hello
I have recently moved to a new property. I am a mosaic artist and have a seat that is made of tiny pieces of mirror. So far the seat has been attacked by 4 angry choughs and today two tiny pardelotes decided to chase the birds in the mirrors away. Since I want the birds to visit my garden I have covered the seat with a sheet to give the birds the impression that they won the territory and successfull chased away the interlopers.
Haha! I’m sure the birds will be very proud of themselves. Thanks for sharing. Did the birds at your old place not attack the seat?
I am very curious about what a bird thinks when it see’s it refection.There is a bird in my yard that keeps comming back to the mirror’s I have no matter where I move them too, it is an on going thing this bird seems to do day and night.I am trying to figure out if this bird loves him self or hate’s what he thinks is another bird.It is the very beginning of summer and there are birds everywhere around but it seems this is the same bird, the reason I think this is because it dose the same thing every time. Although funny for the most part he has ruined a couple of my good mirror’s , I had them out in the yard because I was doing diffrent projects with them but now I dont have the heart to take the mirror’s away from this bird.
Hi Jennifer,
Most likely, the bird hates what he sees as a particularly irritating other bird. Most rival birds would react to his actions in a standard way: if he got aggressive, they would flee or fight, and then if they lost, they would leave. The bird in the mirror reacts in nonsensical ways: he does exactly what the other bird is doing, and only that, and he apparently can’t be defeated in a fight. (I imagine that this is annoying in the same way that someone repeating everything you say was infuriating when you were a child.) In animal behavior we might call this a “super stimulus”: a stimulus that is more extreme than the animal would encounter in natural situations, and therefore may provoke a more extreme reaction.
I’d recommend removing the mirrors: the bird isn’t actually enjoying himself, and he’s wasting time that could be better spent doing pretty much anything else (finding food, building a nest, etc.). There’s also a risk that he’ll crash into the mirror too hard and injure himself.
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I have a mirror on the back of my house. I have heard that this is dangerous for birds as they may fly into it. This does not seem to be an issue in the layout of the space. I am more concerned about what appears to be obsessive behavior of the wild finches and their interactions with the mirror. I argue with myself whether or not to remove the mirror but I am myself obsessed with their behavior. What I presume to be the female, a dull green color, fights the reflection in the same manner you describe with car mirror. The one I believe is the male, a blue with a yellow and red throat, chooses to fly past the mirror doing stunts. I managed to capture decent pictures of him playing in action. I don’t really want to deprive them of what almost seems like a window into more of reality, but I don’t want to hurt them either. Let me know if you are interested in the pictures, we’ll figure out some way to transfer them.
I would be quite interested to see the pictures! My email is klabarbera[at]berkeley.edu if you want to send them. (I’m curious what finches these are – are you in Australia?)
The main potential harms of the mirror are 1) crashing into it and 2) getting stressed out by “fighting” a reflection that never gives up. The risk of #1 depends of the layout of the area: if there’s a large open area where they can get up a lot of speed before hitting the mirror, or (worse) if the mirror is set up in a way that reflect the sky so that they might try to fly THROUGH the mirror, that’s dangerous. If there is vegetation or other obstacles around the mirror and the birds are only flying a meter or so to it, then that seems pretty safe. The risk of #2 depends on the birds’ behavior, and you’ll be the best judge of that: are the birds fighting the mirror CONSTANTLY, and not seeming to take a break? Then consider covering the mirror for part of the day to give them a break.
That might be a good compromise even if you think they’re fine, actually: cover the mirror in the evening, uncover it when you wake up (assuming you don’t rise at dawn like the birds do!). That will give the birds some time without the mirror, and let you continue to enjoy their antics.