Bird nests (cats, trees, leaves, birds)

[azoria]

Most of the trees here are still de-leafed but they'll be leafing out soon. We also seem to have attracted a lot of migratory birds here in Seattle recently. Birds galore all of a sudden.

Without leaves, it's easy to spot bird nests in the trees. Do birds use the same nests year after year or do they build new ones each year?

I've got my eye on a couple of nests but I can't tell if birds are living there or not. And these existing nest have certainly attracted the attention of several local cats so I'm thinking there is bird activity, but I'm not seeing anything.

[Gerania]

I'm not checking the internet, but there's a lot of, what to call it, variation. Some birds use old nests, sites; some only build and use new nests; other birds use the nesting sites of previous inhabitants, other species. Something will likely move into those old nests or build there.

[brokencrayola]

Birds build new ones and also use the ones that already exist.