Which of the following is not a feature of flying birds?

Options

A. Presence of air sacs
B. Presence of keel
C. Presence of copulatory organ
D. Pneumatic bones

Answer

To determine which of the following is not a feature of flying birds, we will analyze each option provided.

### Step-by-Step Solution:

1. **Identify the Features of Flying Birds:**
- We need to consider the characteristics that are typically associated with flying birds (class Aves).

2. **Presence of Air Sacs:**
- Flying birds have air sacs that help in respiration and reduce their overall weight, making it easier for them to fly. This feature is indeed present in flying birds.

3. **Presence of Keel:**
- The keel is a prominent bone found in the sternum of flying birds. It serves as an attachment point for the powerful flight muscles, thus aiding in flight. This feature is also present in flying birds.

4. **Presence of Copulatory Organ:**
- In birds, there are no distinct copulatory organs like those found in mammals. Instead, birds have a cloaca, which serves multiple functions including reproduction. Therefore, the presence of a copulatory organ is not a feature of flying birds.

5. **Presence of Pneumatic Bones:**
- Pneumatic bones are hollow bones that help reduce the weight of the bird, facilitating flight. This feature is present in flying birds.

6. **Conclusion:**
- After analyzing all the options, the feature that is not found in flying birds is the presence of copulatory organs. Hence, the correct answer is the option that states "presence of copulatory organ."

### Final Answer:
The feature that is not found in flying birds is the **presence of copulatory organs**.

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