feather-brained

Extending such a policy to other caged birds would not be a feather-brained idea.

She was herself, Marie Becu, the slangy, light-hearted, feather-brained daughter of the streets; respecting nothing, fearing nothing, confused by nothing—as ready to shriek gutter oaths at her king as at her footman.

Charity, not unsupported by probability, has trusted that Madame de Medalle could not read Latin, but she certainly could read English; and only an utterly corrupted heart, or an incurably dense or feather-brained head, could hide from her the fact that not a few of the English letters she published were damaging to her father’s character.

"What can that feather-brained little woman have been about not to have sent him to school long ago!" was his thought.

The feather-brained flies, on the other hand, to whom the mystery of glass means nothing and who possess no power of thought whatever, merely flutter wildly hither and thither, and end by rushing against the friendly opening that sets them free.