[thedoc (OP)]

Fay Briggs asked the Naked Scientists:
   I heard that due to an asteroid, a giant crater was formed 66 million years ago and the debris wiped out the dinosaurs.  I have also been told that birds are dinosaurs.  So, how did the birds survive?
Regards
What do you think?

[chiralSPO]

My guess is that being warm-blooded is part of it, as both mammals and birds are warm blooded, and only some dinosaurs were...

[evan_au]

It is thought that vaporized rock was blasted into space through the vacuum left behind the falling meteorite. This rock would have condensed in space to small glass beads which fell down through the atmosphere. This is supported by the worldwide distribution of these glass spherules.
See: https://en.wikipedia.org/wiki/Alvarez_hypothesis#Evidence

One theory is that these glass spherules would have rained down through the upper atmosphere, raising the Earth's surface temperature to oven temperatures for a few hours following the impact. Since a ballistic trajectory takes about 45 minutes to reach any point on the Earth, the bombardment would be worldwide within 45 minutes (faster than the speed of sound), and the intensity would have dropped significantly after a few hours.

According to this theory, animals living in burrows would have survived, with perhaps 30cm of soil above them; presumably this would have included small dinosaurs, small birds, small mammals, lizards and animals living in caves. As would aquatic animals like fish and semi-aquatic animals with a low metabolism like crocodiles and turtles that can remain submerged for long periods.