Birds need to know a lot about each other. They need to know things like who will be the best parent; who will pass on the best genes; who could defeat them in a fight; and which offspring is worth investing in the most. One of the ways that birds can perceive such information about each other is by observing each other’s color signals—and the more researchers study these, the more it becomes clear that birds can tell a lot from color alone.
Let’s make up a bird species – the Superb Junco. This imaginary species has a black hood and pink bill like the Oregon Junco, but its body and tail are iridescent blue-violet. Here is an illustration of three individuals of this species:
Although the cuttlefish may be best known for making those flat cuttlefish bones that your pet bird nibbles to get calcium, this paper shows that it should be known for being a lying cheater.
Cuttlefish, like their relatives the squids and the octopuses, are masters of visual communication. They can change their appearance almost instantaneously (video here), and they use color and pattern to say things like “Back off, I’m angry!” and “Pretty lady, I would like to do some romance with you now,” and “Please don’t do romance with me, I am male.”
In many bird species, the males have to acquire and defend a good territory – filled with great food or great places to put a nest – in order to have a prayer of attracting a mate. There’s even evidence that some females pay more attention to the quality of the male’s territory than to the quality of the male, so having a good territory is a big deal.
In these species, males fight a lot. They fight to get territories and then they fight to keep them. It’s a bit like a football game: you have to run fast and smash into people in order to get the ball, and then continue running fast and smashing into people (and withstanding them smashing into you) in order to hang onto it.
All that fighting takes a lot of time and energy, not to mention risk of injury. So the birds (and many other resource-defending animals) have found a less-dangerous shortcut: instead of fighting, they wear “badges of status,” color markings on their body that stand for how tough they are. Birds with less-tough badges don’t bother challenging the tougher birds, and everyone has to fight less. Sounds great, right? It’s the equivalent of a football player wearing a jersey that says “I’m Tougher Than You,” and the other football players just leaving him alone. So much less violent!
… but it doesn’t seem like it should work, does it? If it did, then anybody could put on a jersey that says “I’m Tougher Than Everybody” and win the Superbowl. What stops the birds from lying?
Black-capped Chickadees may be the easiest birds to identify by ear. Chick-a-dee-dee-dee, they sing, telling you exactly who they are. (I’ve heard that towhees do this too, but the towhees I’ve heard always seem to be saying twee or taree, from which I would not be able to get “towhee” unassisted.)Of course, the chick-a-dee sounds like a vocal nametag to us only because someone had the good sense to name chickadees after their call. But it serves as an identifier among the chickadees too. The “chick-a-dee call complex” consists of four note types (the A, B, C, and D notes in a row might be transcribed as chick-k-ka-dee) that can be given in various combinations. Each note type itself can vary in frequency and duration. The chickadees thus have a lot of potential variation to work with, and they do. The D (dee) notes alone indicate both the identity of the individual bird calling, and the flock it belongs too—rather the same way that an Englishman saying “Hello, my name is George,” might indicate to compatriots both his own identity (George) and, in his accent, the region he is affiliated with. When captive chickadees are put into new flocks, the calls of the new flock members change, converging on each other, to indicate their new flock membership.