Biology Why does the professor mention the wood thrush?

Biology
Narrator
Listen to part of a lecture in a biology class. The class is discussing animal behavior.
Professor
OK, the next kind of animal behavior I want to talk about might be familiar to you. You may have seen, for example, a bird that’s in the middle of a mating ritual. And, and suddenly it stops and preens—you know, it takes a few moments to straighten its feathers—and then returns to the mating ritual. This kind of behavior—this doing something that seems completely out of place—is what we call a displacement activity.
Displacement activities are activities that animals engage in when they have conflicting drives—if, if we take our example from a minute ago—if the bird is afraid of its mate, it’s conflicted, it wants to mate, but it’s also afraid and wants to run away, so instead it starts grooming itself. So the displacement activity, the, the grooming, the straightening of its feathers seems to be an irrelevant behavior.
So what do you think another example of a displacement activity might be?
Male student
How about an animal that, um, instead of fighting its enemy or running away, it attacks a plant or a bush?
Professor
That’s a really good suggestion, Carl, but that’s called redirecting. The animal is redirecting its behavior to another object, in this case, the plant or the bush. But that’s not an irrelevant or inappropriate behavior—the behavior makes sense—it’s appropriate under the circumstances, but what doesn’t make sense is the object the behavior’s directed towards. OK, who else? Carol?
Female student
I think I read in another class about an experiment, um, where an object that the animal was afraid of was put next to its food—next to the animal’s food—and the animal, it was conflicted between confronting the object, and eating the food, so instead it just fell asleep. Like that?
Professor
That’s exactly what I mean. Displacement occurs because the animal’s got two conflicting drives, two competing urges, in this case, fear and hunger—and what happens is they inhibit each other—they cancel each other out in a way, and a third, seemingly irrelevant behavior surfaces .. . through a process that we call disinhibition.
Now, in disinhibition, the basic idea is that two drives that seem to inhibit, to hold back a third drive, well, well, they get in the way of each other in a, in a conflict situation, and somehow lose control, lose their inhibiting effect on that third behavior... wh-which means that the third drive surfaces . . . it-it’s expressed in the animal’s behavior.
Now, these displacement activities can include feeding, drinking, grooming, even sleeping. These are what we call "comfort behaviors." So why do you think displacement activities are so often comfort behaviors, such as grooming?
Male student
Maybe because it’s easy for them to do—I mean, grooming is like one of the most accessible things an animal can do—it’s something they do all the time, and they have the-the stimulus right there, on the outside of their bodies in order to do the grooming—or if food is right in front of them. Basically, they don’t have to think very much about those behaviors.
Female student
Professor, isn’t it possible that animals groom because they’ve gotten messed up a little from fighting or mating? I mean, if a bird’s feathers get ruffled, or an animal’s fur—maybe it’s not so strange for them to stop and tidy themselves up at that point.
Professor
That’s another possible reason, although it doesn’t necessarily explain other behaviors such as eating, drinking, or sleeping. What’s interesting is that studies have been done that suggest that the animal’s environment may play a part in determining what kind of behavior it displays. For example, there’s a bird—the wood thrush, anyway when the wood thrush is in an attack-escape conflict—that is, it’s caught between the two urges to escape from or to attack an enemy—if it’s sitting on a horizontal branch, it’ll wipe its beak on its perch. If it’s sitting on a vertical branch, it’ll groom its breast feathers. The immediate environment of the bird—its immediate, um, its relationship to its immediate environment seems to play a part in which behavior it will display.