Here are a few options for a WordPress post_tag description for “成鳥” (Chéngniǎo) in Traditional Chinese, depending on the nuance you want to convey:

**Option 1 (Simple & Direct):**

* **Description:** 已完全發育的鳥類。 (Yǐ wánquán fāyù de niǎolèi.) – Fully developed birds.
* **Use case:** For general categorization of articles about adult birds.

**Option 2 (Slightly More Descriptive):**

* **Description:** 達到性成熟，完成發育的鳥類。 (Dádào xìngchéngshú, wánchéng fāyù de niǎolèi.) – Birds that have reached sexual maturity and completed their development.
* **Use case:** When your posts might discuss aspects of adult bird behavior, breeding, or physiology.

**Option 3 (Emphasizing Contrast with “幼鳥”):**

* **Description:** 相對於幼鳥，已完全長成的鳥類。 (Xiāngduì yú yòuniǎo, yǐ wánquán zhǎngchéng de niǎolèi.) – In contrast to young birds, a type of fully grown birds.
* **Use Case:** Helpful if you’re frequently using the tag “幼鳥” (Young Bird).

**Option 4 (Focusing on Appearance):**

* **Description:** 具有成熟羽毛和完整體型的鳥類。 (Jùyǒu chéngshóu yǔmáo hé wánzhěng tǐxíng de niǎolèi.) – Birds with mature plumage and complete body forms.
* **Use case:** If your posts often highlight visual characteristics.

**How to choose:**

Consider the main themes of your WordPress content. Which aspect of “成鳥” is most relevant to your articles? Choose the description that best reflects the scope of your content and the information you wish to convey to your audience. You can also adjust the length of them if needed!