What is pigeon milk? Give its function.

Explanation

### Step-by-Step Solution:

1. **Definition of Pigeon Milk**:
Pigeon milk is a nutritive secretion produced by the crop glands of female birds, particularly pigeons.

2. **Source of Pigeon Milk**:
The crop is a specialized gland in birds where digestion begins. Birds do not have a stomach in the same way mammals do, so they utilize the crop for the initial stages of digestion.

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