Sirens are masters of deception in the simplest ways possible: song and flattery. In "Siren Song," our speaker is so clever in the way she deceives us that we're never even aware that we're being duped—the entire time. We're too busy loving all of her talk about us being "unique" and special enough to save her. All the while we're hearing "about" the song and being lured to our deaths, we fail to realize that the very thing we want to learn about is the thing we've been hearing all along. So deception, in this case, is best exercised through the flattery of our egos in believing that we are in fact the greatest heroes of all. (Spoiler alert: we are not.)
Deception in "Siren Song" isn't all about lies, but is rather something that is derived from our willingness to assume we are always the hero and/or predator. Wait—you mean we're not all that and a bag of chips?
The speaker's "cry for help" and flattery in the poem are the ultimate mechanisms for deception here. We're caught off-guard by our own egos and eagerness to play the hero. Hey, at least we tried though, right?
As villainous as the Sirens may appear in "Siren Song" and other Greek myths, we also recognize that these ladies are suffering too. Our speaker is isolated with two "feathery maniacs" on an island she can never leave. Sounds like a blast, right? So our villain isn't without her own vulnerabilities and tragedy, which gives her something more than just the flat two-dimensional interpretations we usually see. On a deeper level, we may imagine our speaker as being isolated in her own myth, due to the biases of writers and mythologists who tend to sketch their characters with limiting characteristics.
Being the star of your own myth isn't all it's cracked up to be in "Siren Song." In fact, it becomes the reason why the speaker feels so isolated on that "picturesque" island.
Villains suffer too in "Siren Song," which suggests that they're not always the two-dimensional characters we would like them to be. (Check out Darth Vader in the final minutes of Return of the Jedi for another example.)
Sirens are always women in Greek mythology, so you know there will be some ideas floating around in "Siren Song" regarding women and the femininity they're meant to represent. Sirens are also supposed to be seductive and sexy, so our speaker may be offering some questions about the sexual roles women so often play in literature. These roles, according to our speaker, often appear "picturesque and mythical," which may come across as flat and predictable, rather than something we might encounter in that thing we like to call… oh yeah, real life. It kind of makes sense, then, that the speaker would feel "bored" with that same old song.
The "song" in Atwood's poem is really a symbol for the two-dimensional characteristics that are often used to represent women and femininity in literature. Where's the humanity?
The Siren's not actually bored with her portrayal in literature. It's all part of her elaborate ruse to get us to feel sorry for her. In other words, it's a trap.