Depends on the birds. Some will reuse old nests, fixing them up each year, while others will push the old nest and start again from scratch, while still others will wait until another bird has made a nest and then come in and eat their eggs and take over the nest.
And then cowbirds and cuckoos will just lay their eggs in another bird’s nest and fly away.
Adding to this... some species (eg Kestrels) will use stick nests built by other birds (eg Ravens) after they've finished nesting themselves. Tree hollow nesters (eg Cockatoos) will use a hollow after another species (eg Owl) has finished nesting in the hollow.
Yes, had some smaller birds build a nest on the porch of my rental house - wasn't bothering anyone, so I let them stay rent free. They took nearly the whole summer to raise a bunch of chicks to the point they coukd fly off.
The next summer a larger bird used the nest - but built it up in size and had a bunch of chick's that flew off in a matter of weeks.
I have no idea what kind of birds they were, but the larger did use the smaller birds nest - albeit as a base to build from, not as a complete home.
The house finches that live in my courtyard will reuse the nest if it survived winter. If not they build it in the same place and as far from the other bird nest built on the same beam with a different kind of bird in it.
Em_Adespoton t1_itjqfwz wrote
Depends on the birds. Some will reuse old nests, fixing them up each year, while others will push the old nest and start again from scratch, while still others will wait until another bird has made a nest and then come in and eat their eggs and take over the nest.
And then cowbirds and cuckoos will just lay their eggs in another bird’s nest and fly away.