Tuesday, March 8, 2011

Bird Songs

This is another excerpt from my wife Kate's latest book; Joy of Birding. 

Over the years, I have started to listen to the sounds of my backyard with more purpose.  Who is already out and about?  How many birds are at the feeder?  Are there any squabbles going on yet?  Has someone seen a cat or sent up an alarm about a hawk?  Do I hear any new voices?  Is there a new bird in the forest preparing to set up housekeeping? Are they commenting on the weather?
            I work in an urban area. One evening, I left my office especially late, my head full of worries and concerns over “office stuff”.  As I reached my car, I heard a sound in the vicinity of a tree near by. A beautiful heartfelt song was coming from the branches. I walked over and listened for a few moments.  No need to see him, I knew who he was.  A lovesick male mockingbird, still unmated a little late in the season. In the moonlight, in a pine tree surrounded by highways, skyscrapers and steel, he was pouring out a beautiful song, hoping against hope that somewhere in the concrete jungle a female was waiting for him. For a few moments we shared the evening together, two beings sharing a common understanding.  When I got into my car, my office worries had been replaced. My head, as my daughter used to say, was full of birds.
The variety in bird vocalizations is remarkable. It is a complex and astoundingly beautiful form of communication. Bird sounds take many forms and perform many functions—to attract mates, to warn away others, to communicate with their own species and to announce the boundaries of their territory.  It may seem impossible to try to decipher the seemingly endless variety of sounds, but there are a few basic principles that can help you to understand what birds are saying.

The Song Songbirds make up over half of the world’s bird population.  Bird songs are a series of notes, both short and long, that have a pleasing musical sound. These are the sounds of spring and summer.  The male songbird uses a song to attract a mate. The mating song tends to be complex and elaborate, often with many variations. The nightingale, it is said, has over 300 different love songs at its disposal. Still others, like the cowbird, have been recorded using over 40 different notes. In most species, females listen, but do not respond to these songs.  
Males also use their songs to tell others that this is their territory.  These songs tend to be shorter and simpler. They are meant to tell rival birds where they are and what the boundaries of their property are.  There are gaps in these songs, when the male pauses to listen for answers from possible rivals. 
Though songs are used mostly by males, some species, like the Northern Cardinal, use songs to communicate with each other throughout the season. Both the male and the female sing. Some birds have multiple versions of their song, while others repeat certain phrases over and over.  Still others have single noted songs.   

            Dawn is a busy time for birdsong. Maybe it is because the air is relatively still and the sounds carry better than later in the day. Songs sung at dawn tend to be clearer and more elaborate than songs performed later in the day.  There are also songs sung sotto voce, whispering songs that are often soft renditions of the bird’s regular song, sung during migration, on the nest or in inclement weather.

The Call Calls are short vocalizations that are used by all birds, both male and female. They are used year ’round and have a very specific purpose.  The most common use is to make contact, either with a mate, with other members of their species or with the mixed flock that they are migrating with.          
Flight calls are used by some birds during night migrations or even when they are just flying from perch to perch.
Alarm calls warn the presence of a predator. Some alarm calls are just louder, more urgent versions of the standard contact call, while others are high-pitched and repetitive sirens.
Begging calls are whiny cries performed by juveniles still looking for a handout from their parents.
Some birds can be distinguished from their similar counterparts by their call.  We have a mixed flock of Black-Capped Chickadees and Carolina Chickadees.  Their appearance is virtually identical.  But we can identify them by their different call notes.  The Carolina Chickadee has a higher pitch and a faster pattern than the Black-Capped. Their songs are different too.
On the other hand, our finches are a hopeless blur to us.  If we don’t actually see them, we usually have a hard time figuring out who is in the trees. Is it the House Finch or the Purple Finch? Or could it be a Warbling Vireo?

Mimicry Some birds have a remarkable ability to simulate other bird sounds and even non-bird sounds. The catbird mimics a number of different birds, giving a rival the impression that the territory is already full. The Blue Jay does a great imitation of the Red-shouldered hawk, a skill designed to send his rivals at the bird feeder running for cover.  Starlings, mockingbirds and goldfinches are also excellent mimics.

Non-vocal Communications Birds are not limited by their vocal skills.  Some birds, like the Downy Woodpecker, drum with their beaks to attract females. Clicking noises made by snapping bills and thrumming sounds made by loud wing clapping are also used by males to elicit attention.  The Ruffed Grouse beats the air with his wings and the American Woodcock’s wings make a twittering sound when it flies.

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