A famous quirk: ~羽 is also the traditional counter for rabbits. The usual explanation is that during periods when Buddhist rules discouraged eating four-legged animals, rabbits were counted like birds so they could still be eaten. In everyday modern Japanese you will also hear rabbits (and small birds in casual speech) counted with ~匹 (hiki), but ~羽 is the classic, “correct” choice for birds.
Be warned that ~羽 has some of the most variable readings of any counter. After numbers that end in a small っ sound (6, 8, 10, 100) you often hear ぱ, and after numbers ending in ん (3, 1000, and 何羽) you hear ば - but many speakers, especially nowadays, simply use plain わ everywhere. Both columns below are acceptable; the highlighted readings are the more traditional sound-changed forms.
| No. | Kana | Kanji |
|---|---|---|
| 1 | いちわ | 一羽 |
| 2 | にわ | 二羽 |
| 3 | さんば | 三羽 |
| さんわ | ||
| 4 | よんわ | 四羽 |
| 5 | ごわ | 五羽 |
| 6 | ろっぱ | 六羽 |
| ろくわ | ||
| 7 | ななわ | 七羽 |
| しちわ | ||
| 8 | はっぱ | 八羽 |
| はちわ | ||
| 9 | きゅうわ | 九羽 |
| 10 | じゅっぱ | 十羽 |
| じゅうわ | ||
| 11 | じゅういちわ | 十一羽 |
| 12 | じゅうにわ | 十二羽 |
| 13 | じゅうさんば | 十三羽 |
| じゅうさんわ | ||
| 20 | にじゅうわ | 二十羽 |
| 21 | にじゅういちわ | 二十一羽 |
| 100 | ひゃっぱ | 百羽 |
| ひゃくわ | ||
| 1000 | せんば | 千羽 |
| せんわ | ||
| 10 000 | いちまんば | 一万羽 |
| いちまんわ | ||
| How many | なんば | 何羽 |
| なんわ |
A nice piece of cultural trivia: 千羽鶴 (“a thousand paper cranes”) uses this counter - a string of 1000 origami cranes folded as a wish for healing or good fortune.
Check out other counters.