dinosaurs extinction

Two years in the darkness of the Earth after the asteroid disaster
US scientists concluded that the Earth was dark for two years after being hit by an asteroid 65 million years ago, Phys.org reported yesterday.
Suffering from meteorite disaster but why dinosaurs are extinct, birds are not?
About 66 million years ago, a giant meteorite hit Earth, wiping out three-quarters of all organisms on Earth, and warming the climate for 100,000 years.
Bad luck makes dinosaurs extinct
Asteroids have crashed into Earth at the time of the most vulnerable dinosaurs, leading to the elimination of this animal on the surface of the globe.