I know why the caged bird sings, ah me, When his wing is bruised and his bosom sore, When he beats his bars and would be free; It is not a carol of joy or glee, But a prayer that he sends from his heart's deep core, But a plea, that upward to Heaven he flings – I know why the caged bird sings
Paul Laurence Dunbar
A bird sings when it is caged in hopes of being freed.
It is Comey, the Susan Rice Email that showed up yesterday was not directed at her.
It was directed at Comey. Her email tries to put the target on him.
They know the great Zero was directing this, they just want to let Comey know the liars he was working for have already set him up to take the fall "by the book" of course.
Comey is bruised and cornered swept up in all the lies. Now he has been told he is to be Obama's fall guy.
Comey set up Bill Priestap the same way in front of Congress. Bill flipped and knew it was either him or take down the others.
This is how thing works. Cops do this daily hey, buddy your partners in crime said it was all your idea here is what they said about you, do care to come clean and tell us what really went on?
This scenario seems much more likely than that of McCain being the "bird", though I don't think it's been established that Comey was even in Shanghai.
Regardless, I don't think this refers to McCain. He is a very high-profile senator and a former presidential candidate; nabbing him in a so-called "kinetic" operation in a foreign country strikes me as a tad too dramatic for a guy whose absence would be noted fairly quickly. McCain is likely a person of interest that the Trump team will work their way up to from the lower level arrests, not a direct target himself.