How we cite our quotes:
Shall I tell you the secret
and if I do, will you get me
out of this bird suit? (10-12)
It seems our speaker is feeling a little isolated in her own skin (bird suit) and the role she's supposed to play. She wants out of that "bird suit" and would prefer to be something other than your typical seductive Siren.
I don't enjoy it here
squatting on this island
looking picturesque and mythical (13-15)
The island strikes us as a kind of symbol for our speaker's feelings of isolation in her own "picturesque" myth. She's bored with the two-dimensional world her mythologists have placed her in. So Atwood may also be exploring the biases writers have when characterizing their villains and heroes as archetypes, not people.
with these two feathery maniacs,
I don't enjoy singing
this trio, fatal and valuable. (16-18)
Our speaker may have company (two feathery maniacs), but since they're in the same situation she is (with the same two-dimensional characteristics), she can't expect much excitement or surprises. So she's isolated not only on the island but also by the company she keeps, which offers no chance for a little something different.