Besides pneumatic bones, another useful flight adaptation in birds is

Options

A. Syrinx
B. Pygostyle
C. Furcula
D. Quill feathers

Answer

### Step-by-Step Solution:

1. **Understanding Flight Adaptations in Birds**:
- Birds have several adaptations that enable them to fly efficiently. One of the key adaptations is the presence of pneumatic bones, which are lightweight due to air cavities.

2. **Analyzing the Options**:
- The question provides four options:
- A) Syrinx
- B) Pygostyle
- C) Furcula
- D) Quill Feathers

3. **Evaluating Each Option**:
- **Syrinx**: This is the vocal organ of birds, not directly related to flight.
- **Pygostyle**: This is a bone formed by the fusion of caudal vertebrae, serving as an attachment site for tail feathers, but does not contribute to flight adaptation.
- **Furcula**: Also known as the wishbone, it is a forked bone that strengthens the thoracic skeleton but is not a primary adaptation for flight.
- **Quill Feathers**: These are essential for flight as they provide lift and control. Quill feathers consist of a central stem (scapus), a hollow lower part (calamus), and a solid upper part (rachis). They help in aerodynamics and protection against environmental factors.

4. **Conclusion**:
- After evaluating all the options, it is clear that the quill feathers are another useful flight adaptation in birds besides pneumatic bones. Therefore, the correct answer is **D) Quill Feathers**.