'Bird brain' is no longer a cut down
April 29, 2001

The temperature rises, the barometer reading is low, winds are southerly. Birds common and rare return from their sojourn in warmer climes.

They are rather suddenly evident in our surroundings. This accepted annual event is labeled "migration."

In spite of countless observations, studies and experimentation, this biennial event is a mystery or at best a collection of speculative theories.

There are two basic questions: How do birds migrate and why do they migrate? Other questions that arise "boggle" the human mind. How do they know when to migrate? How do they know the way?

Migration is apparently triggered by a biological urge to migrate called the "sex drive." Day length appears to be a cue, but that theory is not entirely clear.

The "drive" is there, the weather is favorable...a bird heads north, what problems lie ahead?

Method of travel is easy...they can fly. Flying requires energy which is stored as fat. They have to fuel up by eating intensively before they take off, with frequent stop-overs to refuel, on the way.

Many song birds migrate at night. ON moonlit nights their silhouettes may be seen against the moon. this gives them time to feed during the day. Night flight also eliminates the hazards of predators, like hawks. Birds that feed on the wing, such as swallows, migrate during the day.

They are launched and on their way. How do they know where to go? What navigational system do they have? Experiments have shown that they have the ability to navigate by both the sun and the stars.

Their sense of direction is presumed to be an inherited trait. Other suggested aids range from the use of landmarks, low frequency sounds emitted from the earth, and even smells. Scientists can only imagine the array of cues and senses used by birds to find their way.

The term "bird-brain" can be a compliment when taking into consideration that a bird's brain is capable of programming all the information needed to go from their south to north bicultural habitats.

Why do birds migrate? What possible benefit can there be in taking the risk of a northward flight of many miles in the spring.

In temperate climes the spring and summer days are longer than those nearer the equator where they are always the same length. Insects and other invertebrates abound in the temperate zones during the summer growing season.

Long days allow for more hours in which to feed hungry nestlings. In some cases the longer days allow the youngsters to develop faster and the parents might then have a second brood.

Migration questions have puzzled people for centuries. And then there's always the question "Why don't all birds migrate?"

We are grateful to those who spend the winter months with us, but we happily welcome those that return in the spring.