Answer:

There are several causes, among which are:

• The taking into the crop of irritating, indigestible substances
• Overloading the crop
• Eating decomposed meat or other putrid articles
• The presence of parasitic worms in the crop, especially maggots.
  

The organ becomes practically paralyzed and much distended. The contents decompose and ferment and an offensive liquid and gas accumulates as will be indicated by feeling the crop and the belching of the bird.

The crop should be emptied by holding the bird by the legs head downward and gently kneading the organ, thereby forcing the contents out through the mouth.

Keep the bird without food for twelve to eighteen hours and then feed lightly of easily digested foods.

As soon as the crop is emptied give one grain of bicarbonate of soda and one and one-half grains of subnitrate of bismuth in a dessert spoonful of water and repeat the dose once a day for three days.