Name the main nitrogenous waste excreted out in fish and in birds.

Explanation

### Step-by-Step Solution:

1. **Identify the Nitrogenous Waste in Fish:**
- Fish excrete nitrogenous waste primarily in two forms depending on their classification.
- **Cartilaginous Fish:** These fish, such as sharks and rays, excrete urea as their main nitrogenous waste. Urea is less toxic than ammonia and requires a moderate amount of water for excretion.
- **Bony Fish:** These fish, such as salmon and goldfish, excrete ammonia as their primary nitrogenous waste. Ammonia is highly toxic, but since bony fish are often found in freshwater, they can quickly dilute and excrete it in water.

2. **Identify the Nitrogenous Waste in Birds:**
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