To establish the hierarchy in a flock of birds, pecking is normal. However, sometimes malicious pecking may lead to the death of birds.

The possible causes of excessive pecking are:
- high temperatures
- high light intensities
- dust
- poor ventilation
- intestinal disorders
- irriations around the vent
- feed deficiencies (especially protein and salt)
- overcrowding
- lack of feeder space
- boredom

To avoid unnecessary losses by malicious pecking, the beak of birds can be trimmed. Beak trimming is a stressful event and should be done only when it can not be avoided. If trimming is absolutely necessary it must be done properly, because if not, production and welfare will suffer. Poorly beak trimmed flocks have higher mortality and lower uniformity.