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7. Inversion

An inversion layer is a weather phenomenon that is caused by a mass of warm air that is warmer than the air beneath it. Inversion layers are not visible to the naked eye. There are two types of inversion layers that should be of concern to racing pigeon fanciers. One is the high inversion layer that causes an updraught. This layer draws the clouds, air/oxygen, moisture and infra-red from the earth's surface into the upper atmosphere. Racing pigeons are attracted into this type of layer. The reason they are attracted into this layer is because the ultra violet rays required for navigation have been drawn into the upper athmosphere. The birds fly high in search of the navigational elements. The infra red rays that are drawn from the earth's surface causes disorientation and confusion to the birds. The conditions that are evident prior to this type of layer are, clear blue skies, no wind and dead silence with no wild birds to be seen or heard. This layer normally occurs during the warm summer months when the temperature is 25C(78F)or more. These layers occur in various regions around the world. Fanciers frequently lose their young birds, either in the races or from their lofts, after the young birds have entered one of these layers. Please study the two different kinds of inversion described below very carefully.

Two different layers of air an example of inversion

The first one is: high inversion(updraught).

A high inversion layer is shaped like a tornado. Across its mouth it can be 50 miles or more wide and it can be hundreds of miles high. The height of the layer is dependent on the difference in the upper and lower temperatures. The greater the difference the stronger the layer. When youngbirds enter a layer how high they climb is not known. What is important at this stage is their angle of descent. A low angle descent from a high elevation can leave them hundreds or even a thousand miles from home. Whereas if they descend on an obtuse angle they may finish up within a reasonable distance from home. Because of the fact that conditions within a layer are not normal I expect that with the updraft of air and oxygen pigeons would reach heights that would otherwise be impossible for them to reach. After waiting 3 years for suitable conditions to be in place I(Hubert Land) watched some youngbirds I had prepared, enter a layer. I released these young birds at 11.45am and watched with 35x7 binoculars as the birds disappeared out of sight into the elements. Approximately 4 hours later the first young bird arrived back. When I first saw him he was very high and spiralling down. This young bird was disorientated, nervous, confused and appeared to have double vision. This was evident when he tried to land on a telephone pole and missed by about 1 metre. He fell about 3 metres before catching flight again. It appeared as though he saw two separate telephone poles and tried to land on the illusion. Eventually he landed on the loft. The other youngbirds arrived back, each one individually, the last arriving back at 7.30 pm the following evening. Experience shows that young birds surviving entry into a high layer and returning of their own free will make excellent race birds and youngbirds that do not make it back of their own free will are not worth keeping. They will be easily lost if they are raced. Once a young bird has experienced entry into a layer it will avoid entering a layer a second time. It should be noted that while the high inversion layer was in place there was dead silence.There were no wild birds to be seen or heard and no sounds of nature.

Computerized image of inversion layers

The conditions needed for a high inversion are:

-A clear night;
-A temperature in the middle of the day of 25C or more;
-A big difference between day- and night temperature;
-A clear blue sky;
-No clouds;
-No wind;
(Almost always nature is dead silent.)

The second one is: low inversion(downdraught).

The low inversion layer is caused by a downdraught. Warm air traps the cooler air between the clouds and the earth's surface. Inside a low inversion layer racing pigeons or other migratory species cannot navigate. If light winds are present the racing pigeons will follow the wind direction. I(Hubert Land) have only experienced one low layer that had wind associated with it. That wind was very light and came from the east. It takes about two minutes to test for a layer. That test would be carried out at the liberation point. When I am checking the weather conditions that precede a low layer I check for heavy cloud cover, wind conditions, a decrease in temperature that remains constant before the rains that follow a low inversion layer. For the first 25 years of my life I(Hubert Land) lived a stones throw from a railroad track. People in our community kept their clocks set by the train whistle. The trains were always on time. In those days we did not have the weather forecasting we have today. People obtained their weather forecast from the "sound" of the train whistle. A short clear sound indicated good weather, while a long protracted sound guaranteed rain. The reason for this is as follows. In good weather the sound of the whistle disperses quickly into the atmosphere. When there is a low inversion layer present the sound of the whistle bounces off the layer, back to the earth's surface and travels horizontally until it disperses. The inversion layer is like a huge canopy which prevents the birds from seeing the elements they require for navigation. Hence it is not possible for the migratory species to navigate under an inversion layer.

An early morning inversion traps smoke and smog over a big city

Copyright 1998. All rights reserved. Reproduction in whole, in part, in any form or medium, without the express written permission of Steven van Breemen and Hubert Land, is strictly forbidden.

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