Just last weekend I found myself in the cell phone parking lot at Fargo's Hector Airport waiting for family members to return from a brief trip. It was a pleasant afternoon with ample sunshine and little wind. My vehicle windows were down.
A western meadowlark soon announced its presence by singing its loud flute-like song from atop a nearby sign. A few distant meadowlarks could also be heard. Yet during the ten or so minutes I was parked in the lot, I heard only a few other species singing - savannah sparrow, a calling American crow, and a horned lark. Birdsong is noticeably waning.
Time of day, weather conditions and geographical location all play a part in the totality of birdsong. Yet the overriding factor is simply hormones. Birds sing most during the nesting season and can be nearly silent outside of it. Yes, here we are in early August and a distinguishable pullback in the chorus of birds is taking place.
No other group of animals captures our attention by ear quite like birds do. The grunts, barks, growls, and squeals of mammals just don't measure up when taken together. Sure a bugling elk is exciting to listen to and the odd ticking of a porpoise is intriguing but, as a rule, mammals aren't known to be songsters.
Maybe amphibians come close. Here is another order of animals in which vocalizations play a major role in daily life. Certain frogs and toads emit clear and loud noises, mostly at night. Some are even pleasant to our ears. Yet I can't think of any poems or songs written in honor of frog songs; in contrast to the multitudes written about birds.
Among all of us - we and the animals - vocalizing is simply an attempt to do one thing: communicate something. Whether it's to attract a mate, defend a territory, or pass along some other message, vocalizing is a quite common way animals choose to get the point across.
Many birds, for whatever reason, have evolved complex singing abilities. Most are capable of producing sounds which are inarguably pleasing to the human ear, making them attractive to us not only in the visual realm, but aurally as well.
At the heart of bird vocalizations is a structure unique to them called a syrinx, or song box. Similar to our larynx, this organ produces sound by the movement of air over membranous tissue causing vibration. From this seemingly simple structure an amazing array of different sounds are produced by various bird species.
In spring and into summer the primary song of most passerines is a complex one, usually with elaborate vocal patterns, used to define a territory and to announce availability as a mate. This is the song more driven by hormones than the others and the one most easily recognized by people. There was a time a few weeks back when a person couldn't walk outside in the morning and not be overwhelmed at the number of American robins singing their primary song. Not so much anymore.
In addition to songs, songbirds often emit single, mostly unmusical notes experts refer to as "call notes." These are often thought to be innate utterances given for a long list of reasons which include flight calls at night to maintain flock cohesion, alarm notes, contact notes, and so on.
The complexities involved in animal vocalizations, particularly those in birds, have been the focus of much study over the years and undoubtedly will well into the future. Many questions remain unanswered. Why does an ovenbird have a fairly simple primary song while a brown thrasher sings hundreds of variations in a huge repertoire? We don't know for sure.
As we work our way into the heart of August when most all birds have fledged, each morning will sound just a little quieter. Call notes will continue throughout the year and muted versions of songs might too. But for the full-throated deafening morning chorus, we'll have to wait until next May. In the meantime, it might be a good idea to download that birdsong app onto your smart phone or buy those CDs. Next spring you'll be able to identify the bird simply by listening to its song.