What bird was reputedly left out of Noah's ark but had to perch on the roof?

I'm sure not finding anything about a bird being left off the ark during the initial loading. However, 'a raven was sent out by Noah from the ark' (Genesis 8:7) and there is some discussion that he/she "may" have returned, was refused admission and thus perched on the roof.

I have always wondered about this, since the Raven was an unclean bird... why would Noah risk losing the pair? The male raven of the pair sent out? Or the female thrown out? Either way, there's no mention that the Raven came back. So it's mate would have been alone, and it doesn't qualify among the creatures brought in by sevens, because it is an unclean meat.

Gn:8:7: And he sent forth a raven, which went forth to and fro, until the waters were dried up from off the earth. (KJV)

That was a really busy bird... does it say it ever returned to the ark? No.

http://hermeneutics.stackexchange.com/questions/2607/what-was-noah-thinking-when-he-sent-a-raven-from-the-ark

Three birds were sent out to find land, the first two returned as didn't, the third, the raven did not. (satguru)

The ravens may have laid eggs in the ark, since they were supposed to have been on it a very long time. The mate could have gone off and found it. The idea about the bird sitting on top of the ark sounds like an amusing joke tacked on to the story--like the dog plugging a hole in the ark with his nose and thus always having a cold, wet nose.

The KJV doesn't properly render the route of the bird. The Hebrew phrase translated as "to and fro" is "yatzo vashov", wuite literally "leaving and returning" continually until the land was dry - in other words, the raven never went far enough to find land.