Sims can't bird watch on one residential lot

[nocomment]

*Sigh*  It's always something.  I don't think this is important, but I'm curious if it's happened to anyone else.

I have one residential lot where the sims can't bird watch.  Other lots are fine.  I checked and I have Jase's (probably) outdated teen bird watch hack.  Possibly that's a problem? 

[toad]

Try removing it, and see what happens.

[theresatv]

Do you have any trees on the lot? I believe no trees = no birds.

[sloppyhousewife]

Do you have any trees on the lot? I believe no trees = no birds.

Unrelated - I had sims watch birds on lots that had not one single green spot.

[nocomment]

Ok, it turned out to be my own mistake.  I put a floor across the whole second floor, but there are no walls anywhere.  In my mind that means the ground is "outside."  It seems the game doesn't agree.  This finally dawned on me, and I removed some floor tiles.  Underneath that area, they can now bird watch.