Help understanding trailing "ものを" in song lyrics

Question

The following is a stanza from an enka song:

あれから幾つの　流れ星
かぞえた女の　一途な願い
面影胸に　待ちわびて
積丹かもめに　なれるなら
カムイの岬　どこまでも
あなたを探して　飛ぶものを

I get what the lyrics are saying, I'm just wondering what the final "ものを" refers to or what it connects to.

Answer 1

「ものを」 here is a sentence-ending particle expressing a feeling of regret, dissatisfaction, etc. regarding something you have little control over.

In this song, the regret is about being unable to go look for 「あなた」 at will the way the speaker could if she were a 積丹{しゃこたん}かもめ ("a Shakotan seagull").

This 「～～ものを」 is synonymous to 「～～のになあ」、「～～のだがなあ」, etc.

Good question!