Flight requires a constant supply of energy. The chemical energy that fuels flight is contained in the food the birds eat. The bird uses carbohydrates and fats to provide the energy for flight.

Carbohydrates contain four calories per gram. Carbohydrates are available in nectar, fruits and seeds (grains). Although carbohydrates are widely available in the environment, they have the disadvantage of attracting water. The bird can immediately metabolize the carbohydrates it eats or the calories can be stored. For most birds these bulky wet carbohydrates are not an efficient way to store energy.

Carbohydrates can be converted to fat. One gram of fat contains nine calories. Since fat does not absorb water more calories can be stored in less space. Weight is very important to birds that fly. To avoid extra weight most birds do not have large fat stores unless the external temperature is low or they are preparing to migrate.

This week's focus is on the bird's respiratory, cardiovascular and digestive systems. These systems provide and distribute nutrients to all of the bird's cells.

 

Week 4