Brood parasite is

Options

A. Crow
B. Pigeon
C. House sparrow
D. Koel

Answer

### Step-by-Step Solution:

1. **Understanding Brood Parasitism**:
- Brood parasitism is a specific type of parasitism where one bird species lays its eggs in the nest of another bird species. The host bird then unknowingly raises the eggs and chicks of the parasitic bird.

2. **Identifying the Characteristics**:
- In brood parasitism, the parasitic bird typically does not build its own nest. Instead, it relies on the host bird to incubate and feed its young. This behavior can have significant impacts on the host's reproductive success.

3. **Examples of Brood Parasites**:
- One of the most well-known examples of a brood parasite is the **koel**. The koel lays its eggs in the nests of other birds, such as crows or magpies, and the host birds take care of the koel chicks.

4. **Evaluating the Options**:
- Given the options: crow, pigeon, sparrow, and quail, we need to identify which of these is a brood parasite.
- The **koel** is a recognized brood parasite, while the other options (crow, pigeon, sparrow, quail) do not exhibit this behavior.

5. **Conclusion**:
- Therefore, the correct answer to the question "Brood parasite is" is the **koel**.