On: Birds had to relearn flight after meteor wiped out...

[deepsun]

What about tons of regular birds that don't need trees? Eagles, condors, gulls, albatrosses, etc.

[vvanders → deepsun]

Where do you think eagles nest and raise their young before they can learn to fly?

[seszett → vvanders]

Many species of birds nest on the ground or below ground in treeless places though.

[AnimalMuppet → vvanders]

Trees, telephone poles, on the sides of cliffs. No trees or telephone poles? It would limit their range, but not ruin them.

[pfdietz → deepsun]

Species like those likely wouldn't have survived the food web collapse at the extinction.