Infra-sonics and Bird Migration:

There are some migratory birds who can hear ultra-low frequency sounds. This is particularly interesting in light of the fact that unlike elephants or whales - who use these sounds to communicate over long distances, birds don't really produce these sounds; at least they don't produce them from within their bodies.

There is some thought that birds use this ability to help them navigate; and that they have mapped the terrain of their migrations by knowing the sounds of the earth as it is played upon by the weather; how the winds play over mountain ridges like profound, expansive flutes and the waves play the shores in their deep rhythm, slowly modulating the pressures of the earth's atmosphere.

The ability to hear in this manner would allow a flock of birds to determine the scope and breadth of an oncoming storm - days before it's arrival. It might allow them to know if a storm is a result of the seasonal instability of Autumn, or if it is the true onset of Winter.

There was a time when farmers determined the fickle turning of the seasons not by set planting and harvesting dates but by the arrivals and departures of migrating birds; though it is really only in this century of common global travel that bird migration has been considered in geographic terms.

Before this time speculation was varied as to where the birds went. Some believed that they flew to the moon or that they retired into caves and holes in trees to hibernate. There were even those who believed until recently that the swallows would plunge into lakes, descend to the bottom and creep into the mud and slime to sleep until the spring warmed them back to life, whence they would rise to the surface again to take flight.

We know now that something no less miraculous but perhaps a bit more practical occurs; birds follow the seasons across the latitudes of the globe. And while we can easily understand this in terms of their wanting to keep warm in the winter, this doesn't really explain why the Arctic tern flies 22,000 miles yearly from pole to pole when it could just stop in the Bahamas for the chillier months. Clearly something else is happening here. 

A few years ago I was out to Abbott's Lagoon on what has become a regular pilgrimage for me. For those of you who are not familiar with this area, I can tell you that it is an exquisite place to encounter all manner of birds, living and dead. On this one occasion I was walking toward the lower lagoon when I saw a man carrying two bird carcasses; one of a cormorant and the other a grebe. I am always curious about this type of thing so I went over to ask him what he had. First he held up the grebe and said "Patagonia" then the cormorant, saying "Guyana." He said nothing more. This was actually the first time I saw birds from a global perspective.

I feel closer to understanding what migration is about when I see a hummingbird, or the Indian Paintbrush blooming through the summer. Hummingbirds are fond of the paintbrush nectar. There also happens to be a very tiny flower mite that likes it as well. These two creatures have a long standing companionship based on their common tastes; so when the hummingbird dips her beak into the Indian Paintbrush, this mite climbs up into the hummingbirds bill and sets up housekeeping - tidying up the micro-flora and microfauna residing there.

It is the biologically diverse environment in the hummingbird's beak that helps convert her food into the high energy nourishment needed to keep her aloft - so keeping her bill tidy is an important task. In exchange for this service, the hummingbird gives the mite a 5,000 mile lift to the jungles of Peru where it exits - to live out the next stage of it's life in the jungle flowers. For me this ties the Peruvian jungle to the California coast by way of these tiny silver threads of migration. 

When people think of spring it is invariably associated with the return of the songbirds from their wintering grounds. Robins come to mind; and in this area, the redwing blackbirds who saturate the marshes with their cosmic soundfields. But it is Autumn now and if the sounds of birds are less pronounced, they are none-the-less just as dense.

Many songbirds migrate nocturnally; and while they don't generally migrate in flocks, they move by circumstance in groups; keeping tabs on each other by the use of "call notes" or "chip notes" - brief announcements of their presence to other birds of kin. We generally miss these sounds as they often occur thousands of feet up in the air, though they can sometimes be heard in the early hours of dawn as the birds return to earth for the day.

These "chip notes" are a part of bird vocabulary that we understand as "placement tools" - a set of sounds that enable birds establish their presence with each other on the ground and to avoid collision in flight.

A year ago July I was out at the Lagoon watching the seabirds work their nesting grounds. It was a hot, pregnant day with countless species busy securing their nesting areas and gathering food for their offspring. Within this horizon I was transfixed by a tight cluster of hundreds of plovers rapidly ducking and weaving across the body of water. The sound of their collective wing beats was a dense flutter that I can only describe as "butterfly thunder."

It was at the apex of their tight sweeps, when they all silenced their wings for a brief moment that they exclaimed with a volley of chip notes; returning immediately to powered flight. They knew where they were; something larger was binding them together. Since that time I can no longer look at a flock of birds without seeing a single body.

The idea that birds could use sound for navigation may seem extraordinary until you consider sound as a placement tool. We humans have used sound as a vehicle for the conveyance of information; information in the form of words and music. This use of sound is so effective, it tends to eclipse the more fundamental use of sound by all creatures as the perception of location - a tool to we use to explore our surroundings and figure out were we are in them.

Probably the most basic illustration of this lays in the fact that during the development of a human embryo, the second perception to develop after touch through the skin is the perception of balance through the middle ear. This is the gyroscope of our body and allows the fetus to remain upright in the womb. This occurs in the seventh week. It is clear that any creature not distracted by a symbolic vocabulary could have a more complex relationship to their perception of sound.

 Humans tend to measure the capabilities of other species in human terms - and it is amazing how much we miss by doing so. From this perspective, when we think of migrating flocks of geese cutting their deep V's across the fall sky, we think they are organized in some hierarchy with the wise old gander at the lead showing the others the way.

I don't believe it really works this way; I've watched. The foremost position changes -perhaps directed by the shifting density of the winds. The two echelons of geese undulate behind like threads in a stream, taking advantage of the wake of their fellow traveler's forward motion.

When I lived in New York's Hudson Valley I would see the geese comming through in the late Fall – just in front of the deep Winter storms from the North. Often you would know they were approaching before you saw them – you would sort of "hear" them - their approach was palpable. The density of the atmosphere would shift and the next thing you would witness was this apparition pressing across the sky.


Michael Stocker
October 1996 
© 1996 Michael Stocker