There isn’t a season or a time of day birds aren’t singing at Camp Salmen. In springtime when love is in the air, a great variety of birds of a feather are trying to get together, however, mating isn’t the only reason birds call out. Sometimes they’re letting everyone in earshot know it’s their territory or they’re warning others of potential predators in the neighborhood or maybe they’re trying to locate a lost chick. Sometimes it seems they simply want everyone to know how happy they are just to be here. So you’d think that an animal that relies so much on making noise would have big ears to listen; big honking ones like a Fruit Bat, yet they appear to have none.
Birds do, in fact have ears but not external ones. They lack pairs of the sound-gathering devices called “pinna” (ears) found on other animal’s heads. Besides avoiding the obvious problems with wind resistance they seem to do pretty well with just holes located a little behind and below the eyes. These are usually covered with fine feathers for a couple of reasons. One is to keep stuff out of the hole and the other is to function like a foam cover over a blustery politician’s microphone; it filters out the wind noise that flying would bring about. This technique works very well for hawks and owls, Birdland’s best listeners. They can hear clearly enough to concentrate on faint rustlings that betray the presence of a mouse or other prey in the leaf litter down below. Additionally, their ears are lopsided; each is not located on the exact opposite place on their head. This asymmetry makes it easier to more closely determine exactly where the sound is coming from, giving Mr. Mouse even less of a chance of avoiding detection. Oddly enough, what look like ears on Screech and Horned Owls are just ornamental tufts of feathers.
Birds hear about as well as humans. Their inner ear is actually structured like ours with multiple chambers, eardrums, little tapping bones and fluid-filled cochleae containing tiny hairs to translate sound into nerve impulses. Scientists have been able to strap them down and submit them to audio testing to find they are superior in detecting some aspects of sound and come up short in others. See http://www.earthlife.net/birds/hearing.html.
Another vital function of ears for birds is finding and maintaining the pitch-perfect balance they need to operate within the three dimensions they travel. This is very important for an animal that can whip around trees like they do or perch high on a wire to sing their little hearts out and not fall down.